ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 18 Oct 2019 05:00:00 GMT 60 “An effective mutualism? The role of theoretical studies in ecology and evolution” https://amnat.org/an/newpapers/VP-Servedio.html Maria R. Servedio (Feb 2020) What is the role of, and challenges faced by, theoretical studies in ecology and evolution? Read the Article (Just Accepted) In an introductory article to the 2018 Vice-Presidential Symposium collection Maria Servedio briefly reviews how common theory is, how it is perceived by empiricists, and how assumptions made in theoretical studies can pose a challenge to the acceptance of theory. She includes a survey that shows how often citations of theoretical studies in non-theoretical studies are perceived by the theoretical authors as specific and appropriate, as just general to topic, or as incorrect. Although communication of theory to non-theoreticians leaves something to be desired, Servedio includes some recommendations for how the situation might be improved. The article also previews the variety of theoretical papers that comprise the contributions to the Vice-Presidential Symposium collection, including articles by Erol Akçay (on evolution of the game in game theory), Emma Goldberg and Jasmine Foo (on memory in trait macroevolution), Sarah Otto and Alirio Rosales (on the role of narrative in theoretical studies), Paula Vasconcelos and Claus Rueffler (on the evolution of resource specialization), Stephan Peischl and Kimberly Gilbert (on range expansion), Jason Sardell and Mark Kirkpatrick (on sex differences in recombination), and Hanna Kokko (on facultative sex). Abstract Theoretical models often have fundamentally different goals than do empirical studies of the same topic. Models can test the logic of existing hypotheses, explore the plausibility of new hypotheses, provide expectations that can be tested with data, and address aspects of topics that are currently inaccessible empirically. Theoretical models are common in ecology and evolution, and are generally well-cited, but I show that many citations appearing in non-theoretical studies are general to topic and a substantial proportion are incorrect. One potential cause of this pattern is that some functions of models are rather abstract, leading to miscommunication between theoreticians and empiricists. Such misunderstandings are often triggered by simplifying, logistical assumptions that modelers make. The 2018 Vice Presidential Symposium of the American Society of Naturalists included a variety of mathematical models in ecology and evolution from across several topics. Common threads that appear in the use of the models are identified, highlighting the power of a theoretical approach and the role of the assumptions that such models make. More forthcoming papers &raquo; <p>Maria R. Servedio (Feb 2020) </p> <p><b>What is the role of, and challenges faced by, theoretical studies in ecology and evolution? </b></p> <p><i><a href="https://dx.doi.org/10.1086/706814">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n an introductory article to the 2018 Vice-Presidential Symposium collection Maria Servedio briefly reviews how common theory is, how it is perceived by empiricists, and how assumptions made in theoretical studies can pose a challenge to the acceptance of theory. She includes a survey that shows how often citations of theoretical studies in non-theoretical studies are perceived by the theoretical authors as specific and appropriate, as just general to topic, or as incorrect. Although communication of theory to non-theoreticians leaves something to be desired, Servedio includes some recommendations for how the situation might be improved. </p><p>The article also previews the variety of theoretical papers that comprise the contributions to the Vice-Presidential Symposium collection, including articles by Erol Akçay (on evolution of the game in game theory), Emma Goldberg and Jasmine Foo (on memory in trait macroevolution), Sarah Otto and Alirio Rosales (on the role of narrative in theoretical studies), Paula Vasconcelos and Claus Rueffler (on the evolution of resource specialization), Stephan Peischl and Kimberly Gilbert (on range expansion), Jason Sardell and Mark Kirkpatrick (on sex differences in recombination), and Hanna Kokko (on facultative sex). </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>heoretical models often have fundamentally different goals than do empirical studies of the same topic. Models can test the logic of existing hypotheses, explore the plausibility of new hypotheses, provide expectations that can be tested with data, and address aspects of topics that are currently inaccessible empirically. Theoretical models are common in ecology and evolution, and are generally well-cited, but I show that many citations appearing in non-theoretical studies are general to topic and a substantial proportion are incorrect. One potential cause of this pattern is that some functions of models are rather abstract, leading to miscommunication between theoreticians and empiricists. Such misunderstandings are often triggered by simplifying, logistical assumptions that modelers make. The 2018 Vice Presidential Symposium of the American Society of Naturalists included a variety of mathematical models in ecology and evolution from across several topics. Common threads that appear in the use of the models are identified, highlighting the power of a theoretical approach and the role of the assumptions that such models make. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 17 Oct 2019 05:00:00 GMT “Deconstructing evolutionary game theory: coevolution of social behaviors with their evolutionary setting” https://amnat.org/an/newpapers/VP-Akcay-A.html Erol Akçay (Feb 2020) Read the Article (Just Accepted) Abstract Evolution of social behaviors is one of the most fascinating and active fields of evolutionary biology. During the past half century, social evolution theory developed into a mature field with powerful tools to understand the dynamics of social traits such as cooperation under a wide range of conditions. In this paper, I argue that the next stage in the development of social evolution theory should consider the evolution of the setting in which social behaviors evolve. To that end, I propose a conceptual map of the components that make up the evolutionary setting of social behaviors, review existing work that considers the evolution of each component, and discuss potential future directions. The theoretical work reviewed here illustrates how unexpected dynamics can happen when the setting of social evolution itself is evolving, such as cooperation sometimes being self-limiting. I argue that a theory of how the setting of social evolution itself evolves will lead to a deeper understanding of when cooperation and other social behaviors evolve and diversify. More forthcoming papers &raquo; <p>Erol Akçay (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/706811">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>volution of social behaviors is one of the most fascinating and active fields of evolutionary biology. During the past half century, social evolution theory developed into a mature field with powerful tools to understand the dynamics of social traits such as cooperation under a wide range of conditions. In this paper, I argue that the next stage in the development of social evolution theory should consider the evolution of the setting in which social behaviors evolve. To that end, I propose a conceptual map of the components that make up the evolutionary setting of social behaviors, review existing work that considers the evolution of each component, and discuss potential future directions. The theoretical work reviewed here illustrates how unexpected dynamics can happen when the setting of social evolution itself is evolving, such as cooperation sometimes being self-limiting. I argue that a theory of how the setting of social evolution itself evolves will lead to a deeper understanding of when cooperation and other social behaviors evolve and diversify. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT “When synchrony makes the best of both worlds even better: how well do we really understand facultative sex?” https://amnat.org/an/newpapers/VP-Kokko.html Hanna Kokko (Feb 2020) Read the Article (Just Accepted) One can often hear evolutionary biologists describe sexual reproduction as one of the major puzzles in evolutionary theory, sometimes with the addition that facultative sex is an even bigger problem. The problem is that creating offspring sexually is surprisingly inefficient (compared with asexual reproduction), but whenever we are tempted to claim we have understood why sex is on balance selected for, we should also deal with an extra complication: the genetic benefits and economic (demographic) costs scale nonlinearly and do not increase at the same rate when the frequency of sex increases. Very rare sex – for example, once every 100 or 1000 generations – appears, for many models, to be almost as good as obligate sex at producing the adaptive benefit, but it avoids paying the cost in most generations. This is why facultative sex is sometimes stated to offer the best of both worlds, and the consequent puzzle is why not all life is organized that way. This paper does not claim to have found the ultimate solution. Instead, it highlights that existing theories sometimes make simplifications that make the problem mathematically more tractable, but ignore real-life complications that may really matter. One is that facultative sex occurs in synchrony, which links theories of sex with those of bet-hedging. This paper shows why synchrony makes facultative sex even better: if sex is rare, synchrony alleviates mate-finding problems, and if sex has – due to some ecological change – become costlier than before, synchrony helps finding a better rate of sex much more quickly. Abstract Biological diversity abounds in potential study topics. Studies of model systems have their advantages, but reliance on a few well understood cases may create false impressions of what biological phenomena are the ‘norm’. Here I focus on facultative sex, which is often hailed as offering the best of both worlds, in that rare sex offers benefits almost equal to obligate sex, and avoids paying most of the demographic costs. How well do we understand when and why this form of sexual reproduction is expected to prevail? I show several gaps in the theoretical literature, and by contrasting asynchronous with synchronous sex, I highlight the need to link sex theories to the theoretical underpinnings of bet-hedging on the one hand and to mate limitation considerations on the other. Condition-dependent sex, and links between sex with dispersal or dormancy, appear understudied. Simplifications on the one hand are justifiable as a simple assumption structure enhances analytical tractability, but on the other hand, much remains to be done to incorporate key features of real sex to the main theoretical edifice. More forthcoming papers &raquo; <p>Hanna Kokko (Feb 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706812">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>ne can often hear evolutionary biologists describe sexual reproduction as one of the major puzzles in evolutionary theory, sometimes with the addition that facultative sex is an even bigger problem. The problem is that creating offspring sexually is surprisingly inefficient (compared with asexual reproduction), but whenever we are tempted to claim we have understood why sex is on balance selected for, we should also deal with an extra complication: the genetic benefits and economic (demographic) costs scale nonlinearly and do not increase at the same rate when the frequency of sex increases. Very rare sex – for example, once every 100 or 1000 generations – appears, for many models, to be almost as good as obligate sex at producing the adaptive benefit, but it avoids paying the cost in most generations. This is why facultative sex is sometimes stated to offer the best of both worlds, and the consequent puzzle is why not all life is organized that way. This paper does not claim to have found the ultimate solution. Instead, it highlights that existing theories sometimes make simplifications that make the problem mathematically more tractable, but ignore real-life complications that may really matter. One is that facultative sex occurs in synchrony, which links theories of sex with those of bet-hedging. This paper shows why synchrony makes facultative sex even better: if sex is rare, synchrony alleviates mate-finding problems, and if sex has – due to some ecological change – become costlier than before, synchrony helps finding a better rate of sex much more quickly.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>iological diversity abounds in potential study topics. Studies of model systems have their advantages, but reliance on a few well understood cases may create false impressions of what biological phenomena are the ‘norm’. Here I focus on facultative sex, which is often hailed as offering the best of both worlds, in that rare sex offers benefits almost equal to obligate sex, and avoids paying most of the demographic costs. How well do we understand when and why this form of sexual reproduction is expected to prevail? I show several gaps in the theoretical literature, and by contrasting asynchronous with synchronous sex, I highlight the need to link sex theories to the theoretical underpinnings of bet-hedging on the one hand and to mate limitation considerations on the other. Condition-dependent sex, and links between sex with dispersal or dormancy, appear understudied. Simplifications on the one hand are justifiable as a simple assumption structure enhances analytical tractability, but on the other hand, much remains to be done to incorporate key features of real sex to the main theoretical edifice. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT “How does co-evolution of consumer traits affect resource specialization?” https://amnat.org/an/newpapers/VP-Vasconcelos.html Paula Vasconcelos and Claus Rueffler (Feb 2020) How does joint evolution of consumer traits affect resource specialization? Hint: it’s more complicated than you think! Read the Article (Just Accepted) When should we expect the evolution of different resource specialists instead of a single generalists? To simplify the analysis, mathematical models addressing this question are usually based on the assumption of a single evolving consumer trait (think beak size in birds), which led to a pleasingly simple prediction: the evolution of resource specialists is favored by strong trade-offs (where resource generalists perform relatively poorly compared to specialists) while weak trade-offs (where resource generalists perform relatively well) favor the evolution of generalists. However, the assumption of a single evolving consumer trait is not realistic since organisms are complex and the interaction between consumers and their resources is affected by many jointly evolving traits. PhD student Paula Vasconcelos and her supervisor Claus Rueffler from Uppsala University set out to investigate how evolutionary predictions are altered if two or three consumer traits were allowed to jointly evolve. They find that the simple dichotomy suggested by models based on a single evolving trait does not hold true in this more general setting. Instead, weak trade-offs can lead to either one or two specialists, as well as to a single generalist. The reason for these deviating results is that jointly evolving traits can interact in complicated ways in their effect on resource consumption. The results serve as a warning that simplifying assumptions—in this case, that the degree of resource specialization depends on a single trait—must be made carefully, and the results of models that use them should be qualified if the effects of violating these assumptions is unknown. This study touches on another important question in biology: does complexity, as measured in number of jointly evolving traits, facilitates diversification? Surprisingly, the results show that complexity is in fact not a good predictor of diversifying potential as the conditions leading to two specialists are not necessarily more likely to be fulfilled when increasing the number of jointly evolving traits. Abstract Consumers regularly experience trade-offs in their ability to find, handle and digest different resources. Evolutionary ecologists recognized the significance of this observation for the evolution and maintenance of biological diversity long ago and continue to elaborate on the conditions under which to expect one or several specialists, generalists or combinations thereof. Existing theory based on a single evolving trait predicts that specialization requires strong trade-offs such that generalists perform relatively poorly, while weak trade-offs favor a single generalist. Here, we show that this simple dichotomy does not hold true under joint evolution of two or more foraging traits. In this case, the boundary between trade-offs resulting in resource specialists and resource generalists is shifted toward weaker trade-off curvatures. In particular, weak trade-offs can result in evolutionary branching leading to the evolution of two coexisting resource specialists while the evolution of a single resource generalist requires particularly weak trade-offs. These findings are explained by performance benefits due to epistatic trait interactions enjoyed by phenotypes that are specialized in more than one trait for the same resource. More forthcoming papers &raquo; <p>Paula Vasconcelos and Claus Rueffler (Feb 2020) </p> <p><b>How does joint evolution of consumer traits affect resource specialization? Hint: it’s more complicated than you think!</b> </p> <p><i><a href="https://dx.doi.org/10.1086/706813">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hen should we expect the evolution of different resource specialists instead of a single generalists? To simplify the analysis, mathematical models addressing this question are usually based on the assumption of a single evolving consumer trait (think beak size in birds), which led to a pleasingly simple prediction: the evolution of resource specialists is favored by strong trade-offs (where resource generalists perform relatively poorly compared to specialists) while weak trade-offs (where resource generalists perform relatively well) favor the evolution of generalists. However, the assumption of a single evolving consumer trait is not realistic since organisms are complex and the interaction between consumers and their resources is affected by many jointly evolving traits. </p><p>PhD student Paula Vasconcelos and her supervisor Claus Rueffler from Uppsala University set out to investigate how evolutionary predictions are altered if two or three consumer traits were allowed to jointly evolve. They find that the simple dichotomy suggested by models based on a single evolving trait does not hold true in this more general setting. Instead, weak trade-offs can lead to either one or two specialists, as well as to a single generalist. The reason for these deviating results is that jointly evolving traits can interact in complicated ways in their effect on resource consumption. The results serve as a warning that simplifying assumptions—in this case, that the degree of resource specialization depends on a single trait—must be made carefully, and the results of models that use them should be qualified if the effects of violating these assumptions is unknown. </p><p>This study touches on another important question in biology: does complexity, as measured in number of jointly evolving traits, facilitates diversification? Surprisingly, the results show that complexity is in fact not a good predictor of diversifying potential as the conditions leading to two specialists are not necessarily more likely to be fulfilled when increasing the number of jointly evolving traits.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsumers regularly experience trade-offs in their ability to find, handle and digest different resources. Evolutionary ecologists recognized the significance of this observation for the evolution and maintenance of biological diversity long ago and continue to elaborate on the conditions under which to expect one or several specialists, generalists or combinations thereof. Existing theory based on a single evolving trait predicts that specialization requires strong trade-offs such that generalists perform relatively poorly, while weak trade-offs favor a single generalist. Here, we show that this simple dichotomy does not hold true under joint evolution of two or more foraging traits. In this case, the boundary between trade-offs resulting in resource specialists and resource generalists is shifted toward weaker trade-off curvatures. In particular, weak trade-offs can result in evolutionary branching leading to the evolution of two coexisting resource specialists while the evolution of a single resource generalist requires particularly weak trade-offs. These findings are explained by performance benefits due to epistatic trait interactions enjoyed by phenotypes that are specialized in more than one trait for the same resource. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT “Evolution of dispersal can rescue populations from expansion load” https://amnat.org/an/newpapers/VP-Peischl-A.html Stephan Peischl and Kimberly J. Gilbert (Feb 2020) Read the Article (Just Accepted)Abstract Understanding the causes and consequences of range expansions or range shifts has a long history in evolutionary biology. Recent theoretical, experimental, and empirical work has identified two particularly interesting phenomena in the context of species range expansions: (i) gene surfing and the relaxation of natural selection, and (ii) spatial sorting. The former can lead to an accumulation of deleterious mutations at range edges, causing an expansion load and slowing down expansion. The latter can create gradients in dispersal-related traits along the expansion axis and cause an acceleration of expansion. We present a theoretical framework that treats spatial sorting and gene surfing as spatial versions of natural selection and genetic drift, respectively. This model allows us to analytically study how gene surfing and spatial sorting interact and derive the probability of fixation of pleiotropic mutations at the expansion front. We use our results to predict the co-evolution of mean fitness and dispersal rates, taking into account the effects of random genetic drift, natural selection, and spatial sorting, as well as correlations between fitness- and dispersal-related traits. We identify a “rescue effect” of spatial sorting, where the evolution of higher dispersal rates at the leading edge rescues the population from incurring expansion load. More forthcoming papers &raquo; <p>Stephan Peischl and Kimberly J. Gilbert (Feb 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/705993">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>nderstanding the causes and consequences of range expansions or range shifts has a long history in evolutionary biology. Recent theoretical, experimental, and empirical work has identified two particularly interesting phenomena in the context of species range expansions: (i) gene surfing and the relaxation of natural selection, and (ii) spatial sorting. The former can lead to an accumulation of deleterious mutations at range edges, causing an expansion load and slowing down expansion. The latter can create gradients in dispersal-related traits along the expansion axis and cause an acceleration of expansion. We present a theoretical framework that treats spatial sorting and gene surfing as spatial versions of natural selection and genetic drift, respectively. This model allows us to analytically study how gene surfing and spatial sorting interact and derive the probability of fixation of pleiotropic mutations at the expansion front. We use our results to predict the co-evolution of mean fitness and dispersal rates, taking into account the effects of random genetic drift, natural selection, and spatial sorting, as well as correlations between fitness- and dispersal-related traits. We identify a &ldquo;rescue effect&rdquo; of spatial sorting, where the evolution of higher dispersal rates at the leading edge rescues the population from incurring expansion load. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT Nominations for the Sewall Wright Award https://amnat.org/announcements/NomWright.html The American Society of Naturalists invites nominations for the 2020 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator who is making fundamental contributions to the Society’s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2020 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society. The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all areas of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years. The names of former recipients can be found here: https://www.amnat.org/awards.html#Wright For the 2020 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by January 15, 2020, via e-mail to Monica Geber (mag9@cornell.edu). Please indicate “Sewall Wright Award” in the subject line and let the filename of the nomination letter indicate the name of the nominee. <p>The American Society of Naturalists invites nominations for the 2020 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator who is making fundamental contributions to the Society&rsquo;s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2020 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all areas of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years.</p> <p>The names of former recipients can be found here:<br /> <a href="https://www.amnat.org/awards.html#Wright">https://www.amnat.org/awards.html#Wright</a></p> <p>For the 2020 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by January 15, 2020, via e-mail to Monica Geber (<a href="mailto:mag9@cornell.edu">mag9@cornell.edu</a>). Please indicate &ldquo;Sewall Wright Award&rdquo; in the subject line and let the filename of the nomination letter indicate the name of the nominee.</p> Tue, 15 Oct 2019 05:00:00 GMT Nominations for the Edward O. Wilson Naturalist Award https://amnat.org/announcements/NomEOWilson.html The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career (within 25 years of completion of the PhD) who has made significant contributions to the knowledge of a particular ecosystem or group of organisms.&nbsp;Time since PhD degree can be extended in light of parental leave. Other forms of exceptional caregiving responsibility [e.g., partner, spouse, aged parent, etc]. or extenuating circumstances will be considered on a case-by-case basis. Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. The recipient need not be a member of the Society. The award will consist of an especially appropriate work of art and a prize of $2,000. The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;https://www.amnat.org/awards.html#Wilson Nominations will be held over for two years. The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 15, 2020, to Joe Travis (travis@bio.fsu.edu). Please indicate "E. O. Wilson Award" in the subject line.&nbsp; <p>The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career (within 25 years of completion of the PhD) who has made significant contributions to the knowledge of a particular ecosystem or group of organisms.&nbsp;Time since PhD degree can be extended in light of parental leave. Other forms of exceptional caregiving responsibility [e.g., partner, spouse, aged parent, etc]. or extenuating circumstances will be considered on a case-by-case basis.</p> <p>Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. <em>The recipient need not be a member of the Society</em>. The award will consist of an especially appropriate work of art and a prize of $2,000.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;<a href="https://www.amnat.org/awards.html#Wilson">https://www.amnat.org/awards.html#Wilson</a></p> <p>Nominations will be held over for two years.</p> <p>The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 15, 2020, to Joe Travis (<a href="mailto:travis@bio.fsu.edu">travis@bio.fsu.edu</a>). Please indicate &quot;E. O. Wilson Award&quot; in the subject line.&nbsp;</p> Tue, 15 Oct 2019 05:00:00 GMT Listen to Diverse Scientists Tell Their Stories--Story Collider 2019 https://amnat.org/announcements/ANNCollider.html This was a moving, edifying, and entertaining evening. As Samuel Scarpino said on Twitter: "The @storycollider x @Evol_mtg crossover was by far the best conference event I&#39;ve attended.&nbsp; It was inspiring, humbling, and emotional.&nbsp; I can&#39;t recommend listening to these scientists tell their stories enough." Aparna Agarwal https://soundcloud.com/sse-communications/aparna-agarwal-story-collider-evolution-2019 Patty Brennan https://soundcloud.com/sse-communications/patty-brennan-story-collider-evolution-2019 Ambika Kamath https://soundcloud.com/sse-communications/ambika-kamath-story-collider-evolution-2019 C. Brendan Ogbunu https://soundcloud.com/sse-communications/c-brandon-ogbunu-story-collider-evolution-2019 Scott Taylor https://soundcloud.com/sse-communications/scott-taylor-story-collider-evolution-2019 Stories are powerful. Whether hilarious or heartbreaking, subversive or soothing, it matters who takes the stage and what stories are told. On June 23, 2019, The Story Collider hosted a live show at the Evolution Meetings in Providence. This event is co-organized by the Diversity Committees of the ASN, SSB, and SSE with the goal of highlighting the diverse voices of evolutionary biology!The Story Collider producers and event organizers worked with the volunteers who offered stories: about almost anything—an important experiment, a rough day in the field, misadventure, love, loss, and more; but it must be about you. Our format does not include slides or props.It’s about lived experiences. Exotic locations and exciting action never hurt, but what we care about is how you’ve grown as a result of the events in your life. If you’re selected for the show, experienced Story Collider producers will work with you for more than a month to help you prepare. <p>This was a moving, edifying, and entertaining evening. As Samuel Scarpino said on Twitter: &quot;The @storycollider x @Evol_mtg crossover was by far the best conference event I&#39;ve attended.&nbsp; It was inspiring, humbling, and emotional.&nbsp; I can&#39;t recommend listening to these scientists tell their stories enough.&quot;</p> <ul> <li>Aparna Agarwal <a href="https://soundcloud.com/sse-communications/aparna-agarwal-story-collider-evolution-2019">https://soundcloud.com/sse-communications/aparna-agarwal-story-collider-evolution-2019</a></li> <li>Patty Brennan <a href="https://soundcloud.com/sse-communications/patty-brennan-story-collider-evolution-2019">https://soundcloud.com/sse-communications/patty-brennan-story-collider-evolution-2019</a></li> <li>Ambika Kamath <a href="https://soundcloud.com/sse-communications/ambika-kamath-story-collider-evolution-2019">https://soundcloud.com/sse-communications/ambika-kamath-story-collider-evolution-2019</a></li> <li>C. Brendan Ogbunu <a href="https://soundcloud.com/sse-communications/c-brandon-ogbunu-story-collider-evolution-2019">https://soundcloud.com/sse-communications/c-brandon-ogbunu-story-collider-evolution-2019</a></li> <li>Scott Taylor <a href="https://soundcloud.com/sse-communications/scott-taylor-story-collider-evolution-2019">https://soundcloud.com/sse-communications/scott-taylor-story-collider-evolution-2019</a></li> </ul><p>Stories are powerful. Whether hilarious or heartbreaking, subversive or soothing, it matters who takes the stage and what stories are told. On June 23, 2019, The Story Collider hosted a live show at the Evolution Meetings in Providence. This event is co-organized by the Diversity Committees of the ASN, SSB, and SSE with the goal of highlighting the diverse voices of evolutionary biology!</p><p>The Story Collider producers and event organizers worked with the volunteers who offered stories: about almost anything&mdash;an important experiment, a rough day in the field, misadventure, love, loss, and more; but it must be about you. Our format does not include slides or props.It&rsquo;s about lived experiences. Exotic locations and exciting action never hurt, but what we care about is how you&rsquo;ve grown as a result of the events in your life. If you&rsquo;re selected for the show, experienced Story Collider producers will work with you for more than a month to help you prepare.</p> Tue, 15 Oct 2019 05:00:00 GMT Nominations for the Joint Council IDEA Award https://amnat.org/announcements/NomIDEAaward.html The American Society of Naturalists, the Society for the Study of Evolution, and the Society of Systematic Biologists announce the call for nominations for the 1st annual ASN/SSE/SSB Inclusiveness, Diversity, Equity, and Access (IDEA) Award. The IDEA Award will be given to a person at any career stage who has strengthened the ecology and evolutionary biology community by promoting inclusiveness and diversity in our fields. The award can also be presented to a group. The recipient will receive a plaque at the annual meeting of ASN/SSB/SSE and a $1000 honorarium. ***Eligibility Note: No contemporary officer, editor, member of diversity committee, or meeting organizer of the three societies is eligible for the award.*** Nomination packages should include: 1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A single letter including biographical information (name, title, organization) of the person or group being nominated, along with a short description (300 words or less) of the activities supporting the nomination.&nbsp; The letter must also include a section on the nature of impact the person or group has had on inclusivity, diversity, and equity in the field. &nbsp; 2)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A brief biosketch or list of activities (maximum 3 pages) for the person/group nominated. 3)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Self-nominations are welcome and should be accompanied by a letter of support for the nomination from someone familiar with the activities of the nominee. Nominations should be submitted by January 15, 2020 by going to the award nomination form: http://bit.ly/evoidea <p>The American Society of Naturalists, the Society for the Study of Evolution, and the Society of Systematic Biologists announce the call for nominations for the 1st annual ASN/SSE/SSB Inclusiveness, Diversity, Equity, and Access (IDEA) Award. The IDEA Award will be given to a person at any career stage who has strengthened the ecology and evolutionary biology community by promoting inclusiveness and diversity in our fields. The award can also be presented to a group. The recipient will receive a plaque at the annual meeting of ASN/SSB/SSE and a $1000 honorarium.</p> <p>***Eligibility Note: No contemporary officer, editor, member of diversity committee, or meeting organizer of the three societies is eligible for the award.***</p> <p><strong>Nomination packages should include:</strong></p> <p>1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A single letter including biographical information (name, title, organization) of the person or group being nominated, along with a short description (300 words or less) of the activities supporting the nomination.&nbsp; The letter must also include a section on the nature of impact the person or group has had on inclusivity, diversity, and equity in the field. &nbsp;</p> <p>2)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A brief biosketch or list of activities (maximum 3 pages) for the person/group nominated.</p> <p>3)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Self-nominations are welcome and should be accompanied by a letter of support for the nomination from someone familiar with the activities of the nominee.</p> <p>Nominations should be submitted by January 15, 2020 by going to the award nomination form: <a href="http://bit.ly/evoidea">http://bit.ly/evoidea</a></p> Mon, 14 Oct 2019 05:00:00 GMT Call for Nominations for ASN President and Vice President https://amnat.org/announcements/NomASNOfficersANN.html Members of the American Society of Naturalists are encouraged to submit nominations for the Executive Committee (EC). Elections will be held in 2020 for President and Vice President. The President serves on the EC from 2021-2025, acting as President in 2022 The Vice President serves on the EC from 2021-2023, acting as VP in 2022. The VP organizes a symposium to be presented at the meetings in 2022 and edits the symposium papers for publication in The American Naturalist. Names of nominees for specific offices should be submitted by January 15, 2020, to Megan Frederickson (m.frederickson@utoronto.ca) Please indicate “ASN Nomination” in the subject line. As you contemplate nominations, you may want to check the current (https://www.amnat.org/about/governance/execcomm.html) and past officers (https://www.amnat.org/about/history/past-ec.html) for reference. &nbsp;The PRESIDENT leads the ASN Executive Council and selects the membership of the award and officer nomination committees. The President selects the President’s Award for the “best” paper in The American Naturalist in the past year, gives the ASN Presidential Address and presents the Society’s awards at the annual meeting, and represents the ASN in multiple other ways through the year. The President serves on the Executive Council for five years, including one year as President-Elect and three years as a Past-President. The VICE PRESIDENT organizes the Vice-President’s Symposium for the annual meeting and edits the special supplement to The American Naturalist that contains the papers derived from the VP Symposium. The Vice-President is also the Society’s liaison for the organizers of the annual meeting. The Vice-President serves as a member of the Executive Council for three years, two as a regular member and one as ex officio member. <p>Members of the American Society of Naturalists are encouraged to submit nominations for the Executive Committee (EC). Elections will be held in 2020 for President and Vice President.</p> <ul> <li>The President serves on the EC from 2021-2025, acting as President in 2022</li> <li>The Vice President serves on the EC from 2021-2023, acting as VP in 2022. The VP organizes a symposium to be presented at the meetings in 2022 and edits the symposium papers for publication in <em>The American Naturalist</em>.</li> </ul> <p><strong>Names of nominees for specific offices should be submitted by January 15, 2020, to Megan Frederickson (<a href="mailto:m.frederickson@utoronto.ca?subject=ASN%20Nomination">m.frederickson@utoronto.ca</a>)</strong></p> <p>Please indicate &ldquo;ASN Nomination&rdquo; in the subject line.</p> <p>As you contemplate nominations, you may want to check the current (<a href="https://www.amnat.org/about/governance/execcomm.html">https://www.amnat.org/about/governance/execcomm.html</a>) and past officers (<a href="https://www.amnat.org/about/history/past-ec.html)">https://www.amnat.org/about/history/past-ec.html)</a> for reference.</p> <p>&nbsp;</p><p>The <strong>PRESIDENT </strong>leads the ASN Executive Council and selects the membership of the award and officer nomination committees. The President selects the President&rsquo;s Award for the &ldquo;best&rdquo; paper in <em>The American Naturalist </em>in the past year, gives the ASN Presidential Address and presents the Society&rsquo;s awards at the annual meeting, and represents the ASN in multiple other ways through the year. The President serves on the Executive Council for five years, including one year as President-Elect and three years as a Past-President.</p> <p>The <strong>VICE PRESIDENT </strong>organizes the Vice-President&rsquo;s Symposium for the annual meeting and edits the special supplement to <em>The American Naturalist </em>that contains the papers derived from the VP Symposium. The Vice-President is also the Society&rsquo;s liaison for the organizers of the annual meeting. The Vice-President serves as a member of the Executive Council for three years, two as a regular member and one as ex officio member.</p> Mon, 14 Oct 2019 05:00:00 GMT “Theory in service of narratives in evolution and ecology” https://amnat.org/an/newpapers/VP-Otto.html Sarah P. Otto and Alirio Rosales (Feb 2020) Read the Article (Just Accepted)Abstract Considering the role of theory in ecology and evolution, we argue that scientific theorizing involves an interplay between narratives and models in which narratives play a key creative and organizing role. Specifically, as scientists, we reason through the use of narratives that explain biological phenomena by envisaging, or mentally simulating, causal paths leading from a plausible initial state to an outcome of interest. Within these narratives, parts may appear clear, while others puzzling. It is at these tenuous junctions – junctions where reasoning is made challenging by conflicting possible outcomes – that we often build mathematical models to support and extend, or reject and revise, our narratives. Accordingly, models, both analytical and computational, are framed by and interpreted within a narrative. We illustrate these points using case studies from population genetics. This perspective on scientific theorizing helps to clarify the nature of theoretical debates, which often arise from the narratives in which math is embedded, not from the math itself. Finally, this perspective helps place appropriate creative weight on the importance of developing, revising, and challenging narratives in the scientific enterprise. More forthcoming papers &raquo; <p>Sarah P. Otto and Alirio Rosales (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/705991">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsidering the role of theory in ecology and evolution, we argue that scientific theorizing involves an interplay between narratives and models in which narratives play a key creative and organizing role. Specifically, as scientists, we reason through the use of narratives that explain biological phenomena by envisaging, or mentally simulating, causal paths leading from a plausible initial state to an outcome of interest. Within these narratives, parts may appear clear, while others puzzling. It is at these tenuous junctions – junctions where reasoning is made challenging by conflicting possible outcomes – that we often build mathematical models to support and extend, or reject and revise, our narratives. Accordingly, models, both analytical and computational, are framed by and interpreted within a narrative. We illustrate these points using case studies from population genetics. This perspective on scientific theorizing helps to clarify the nature of theoretical debates, which often arise from the narratives in which math is embedded, not from the math itself. Finally, this perspective helps place appropriate creative weight on the importance of developing, revising, and challenging narratives in the scientific enterprise. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Sex differences in the recombination landscape” https://amnat.org/an/newpapers/VP-Sardell.html Jason M. Sardell and Mark Kirkpatrick (Feb 2020) Read the Article (Just Accepted)Abstract Sex differences in overall recombination rates are well known, but little theoretical or empirical attention has been given to how and why sexes differ in their recombination landscapes: the patterns of recombination along chromosomes. In the first scientific review of this phenomenon, we find that recombination is biased towards telomeres in males and more uniformly distributed in females in most vertebrates and many other eukaryotes. Notable exceptions to this pattern exist, however. Fine scale recombination patterns also frequently differ between males and females. The molecular mechanisms responsible for sex-differences remain unclear, but chromatin landscapes play a role. Why these sex differences evolve also is unclear. Hypotheses suggest that they may result from sexually antagonistic selection acting on coding genes and their regulatory elements, meiotic drive in females, selection during the haploid phase of the life cycle, selection against aneuploidy, or mechanistic constraints. No single hypothesis, however, can adequately explain the evolution of sex differences in all cases. Sex-specific recombination landscapes have important consequences for population differentiation and sex chromosome evolution. More forthcoming papers &raquo; <p>Jason M. Sardell and Mark Kirkpatrick (Feb 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/704943">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>ex differences in overall recombination rates are well known, but little theoretical or empirical attention has been given to how and why sexes differ in their recombination landscapes: the patterns of recombination along chromosomes. In the first scientific review of this phenomenon, we find that recombination is biased towards telomeres in males and more uniformly distributed in females in most vertebrates and many other eukaryotes. Notable exceptions to this pattern exist, however. Fine scale recombination patterns also frequently differ between males and females. The molecular mechanisms responsible for sex-differences remain unclear, but chromatin landscapes play a role. Why these sex differences evolve also is unclear. Hypotheses suggest that they may result from sexually antagonistic selection acting on coding genes and their regulatory elements, meiotic drive in females, selection during the haploid phase of the life cycle, selection against aneuploidy, or mechanistic constraints. No single hypothesis, however, can adequately explain the evolution of sex differences in all cases. Sex-specific recombination landscapes have important consequences for population differentiation and sex chromosome evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Memory in trait macroevolution” https://amnat.org/an/newpapers/VP-Goldberg.html Emma E. Goldberg and Jasmine Foo (Feb 2020) Read the Article (Just Accepted)Abstract The history of a trait within a lineage may influence its future evolutionary trajectory, but macroevolutionary theory of this process is not well developed. For example, consider the simplified binary trait of living in cave versus surface habitat. The longer a species has been cave-dwelling, the more may accumulated loss of vision, pigmentation, and defense restrict future adaptation if the species encounters the surface environment. However, the Markov model of discrete trait evolution that is widely adopted in phylogenetics does not allow the rate of cave-to-surface transition to decrease with longer duration as a cave-dweller. Here, we describe three models of evolution that remove this ‘memory-less’ constraint, using a renewal process to generalize beyond the typical Poisson process of discrete trait macroevolution. We then show how the two-state renewal process can be used for inference, and we investigate the potential of phylogenetic comparative data to reveal different influences of trait duration, or ‘memory’ in trait evolution. We hope that such approaches may open new avenues for modeling trait evolution and for broad comparative tests of hypotheses that some traits become entrenched. More forthcoming papers &raquo; <p>Emma E. Goldberg and Jasmine Foo (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/705992">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he history of a trait within a lineage may influence its future evolutionary trajectory, but macroevolutionary theory of this process is not well developed. For example, consider the simplified binary trait of living in cave versus surface habitat. The longer a species has been cave-dwelling, the more may accumulated loss of vision, pigmentation, and defense restrict future adaptation if the species encounters the surface environment. However, the Markov model of discrete trait evolution that is widely adopted in phylogenetics does not allow the rate of cave-to-surface transition to decrease with longer duration as a cave-dweller. Here, we describe three models of evolution that remove this &lsquo;memory-less&rsquo; constraint, using a renewal process to generalize beyond the typical Poisson process of discrete trait macroevolution. We then show how the two-state renewal process can be used for inference, and we investigate the potential of phylogenetic comparative data to reveal different influences of trait duration, or &lsquo;memory&rsquo; in trait evolution. We hope that such approaches may open new avenues for modeling trait evolution and for broad comparative tests of hypotheses that some traits become entrenched. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Social games and genic selection drives mammalian mating system evolution and speciation” https://amnat.org/an/newpapers/Feb-Sinervo.html Barry Sinervo, Alexis S. Chaine, and Donald Miles (Feb 2020) Genes drive mating system evolution in models and rodents Read the Article (Just Accepted) Whether animals partner with just one mate or with many, or even if individuals in a population differ in their mating patterns, has largely been explained by control over territorial resources. In an upcoming issue of The&nbsp;American Naturalist, researchers from the US and France have proposed a new explanation: genes for three alternative behaviors of aggression, sneaking, and the combination of cooperation and care that underlie both mating and social behavior can drive the evolution of mating patterns. The research team used mathematical models to describe mating system evolution based on genes for male-male competition (vs. cooperation), choice of neighborhoods, and paternal care premised on shared genes between interacting individuals. Using published data on rodent mating behavior, they then tested whether the predictions generated by their genetic model captured patterns in mating system while ignoring resource distribution. Rodents exhibit behaviors that the researchers modeled, including alternative mating tactics, genetic recognition, and paternal care, which are often linked to specific genes identified in molecular studies. Both distribution of mating systems and reconstruction of the evolutionary history of rodent mating systems among 288 species across all families match predictions of the model. Interestingly, cooperation and care behaviors associated with a monogamous mating strategy moves species from a mixed-mating system containing alternative strategies towards either monogamous or polygynous species and accelerates speciation. Monogamy in rodents (~20%) is far more common than previously believed. Taken together, these findings open a new possibility for what drives mating patterns: genes that underlie cooperative and care behavior linked to how you interact with offspring and neighbors and drive a rock-paper-scissors (RPS) dynamic among alternative behavioral types. The model generalizes the RPS game from mating dynamics to speciation across vertebrate classes and other organisms. Abstract Mating system theory based on economics of resource defense has been applied to describe social system diversity across taxa. Such models are generally successful, but fail to account for stable mating systems across different environments or shifts in mating system without a change in ecological conditions. We propose an alternative approach to resource defense theory based on frequency dependent competition among genetically determined alternative behavioral strategies characterizing many social systems (polygyny, monogamy, sneak). We modeled payoffs for competition, neighborhood choice, and paternal care to determine evolutionary transitions among mating systems. Our model predicts 4 stable outcomes driven by the balance between cooperative and agonistic behaviors: promiscuity (2 or 3 strategies), polygyny, and monogamy. Phylogenetic analysis of 288 rodent species support assumptions of our model and is consistent with patterns of evolutionarily stable states and mating system transitions. Support for model assumptions include monogamy and polygyny evolve from promiscuity and paternal care and monogamy are coadapted in rodents. As predicted by our model, monogamy and polygyny occur in sister taxa among rodents more often than chance. Transitions to monogamy also favor higher speciation rates in subsequent lineages, relative to polygynous sister lineages. Taken together, our results suggest that genetically based neighborhood choice behavior and paternal care can drive transitions in mating system evolution. While our genic mating system theory could complement resource based theory, it can explain mating system transitions regardless of resource distribution and provides alternative explanations such as evolutionary inertia when resource ecology and mating systems do not match. More forthcoming papers &raquo; <p>Barry Sinervo, Alexis S. Chaine, and Donald Miles (Feb 2020) </p> <p><b>Genes drive mating system evolution in models and rodents </b></p> <p><i><a href="https://dx.doi.org/10.1086/706810">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hether animals partner with just one mate or with many, or even if individuals in a population differ in their mating patterns, has largely been explained by control over territorial resources. In an upcoming issue of <i>The&nbsp;American Naturalist</i>, researchers from the US and France have proposed a new explanation: genes for three alternative behaviors of aggression, sneaking, and the combination of cooperation and care that underlie both mating and social behavior can drive the evolution of mating patterns. The research team used mathematical models to describe mating system evolution based on genes for male-male competition (vs. cooperation), choice of neighborhoods, and paternal care premised on shared genes between interacting individuals. Using published data on rodent mating behavior, they then tested whether the predictions generated by their genetic model captured patterns in mating system while ignoring resource distribution. Rodents exhibit behaviors that the researchers modeled, including alternative mating tactics, genetic recognition, and paternal care, which are often linked to specific genes identified in molecular studies. Both distribution of mating systems and reconstruction of the evolutionary history of rodent mating systems among 288 species across all families match predictions of the model. Interestingly, cooperation and care behaviors associated with a monogamous mating strategy moves species from a mixed-mating system containing alternative strategies towards either monogamous or polygynous species and accelerates speciation. Monogamy in rodents (~20%) is far more common than previously believed. Taken together, these findings open a new possibility for what drives mating patterns: genes that underlie cooperative and care behavior linked to how you interact with offspring and neighbors and drive a rock-paper-scissors (RPS) dynamic among alternative behavioral types. The model generalizes the RPS game from mating dynamics to speciation across vertebrate classes and other organisms.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ating system theory based on economics of resource defense has been applied to describe social system diversity across taxa. Such models are generally successful, but fail to account for stable mating systems across different environments or shifts in mating system without a change in ecological conditions. We propose an alternative approach to resource defense theory based on frequency dependent competition among genetically determined alternative behavioral strategies characterizing many social systems (polygyny, monogamy, sneak). We modeled payoffs for competition, neighborhood choice, and paternal care to determine evolutionary transitions among mating systems. Our model predicts 4 stable outcomes driven by the balance between cooperative and agonistic behaviors: promiscuity (2 or 3 strategies), polygyny, and monogamy. Phylogenetic analysis of 288 rodent species support assumptions of our model and is consistent with patterns of evolutionarily stable states and mating system transitions. Support for model assumptions include monogamy and polygyny evolve from promiscuity and paternal care and monogamy are coadapted in rodents. As predicted by our model, monogamy and polygyny occur in sister taxa among rodents more often than chance. Transitions to monogamy also favor higher speciation rates in subsequent lineages, relative to polygynous sister lineages. Taken together, our results suggest that genetically based neighborhood choice behavior and paternal care can drive transitions in mating system evolution. While our genic mating system theory could complement resource based theory, it can explain mating system transitions regardless of resource distribution and provides alternative explanations such as evolutionary inertia when resource ecology and mating systems do not match. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Shared patterns of genome-wide differentiation are more strongly predicted by geography than by ecology” https://amnat.org/an/newpapers/Feb-Rennison-A.html Diana J. Rennison, Kira E. Delmore, Kieran Samuk, Gregory L. Owens, and Sara E. Miller (Feb 2020) Geographic proximity of populations strongly predicts magnitude of parallel genomic differentiation Read the Article (Just Accepted) Abstract Closely related populations often display similar patterns of genomic differentiation, yet it remains an open question which ecological and evolutionary forces generate these patterns. The leading hypothesis is that this similarity in divergence is driven by parallel natural selection. However, several recent studies have suggested that these patterns may instead be a product of the depletion of genetic variation that occurs as result of background selection (i.e. linked negative selection). To date, there have been few direct tests of these competing hypotheses. To determine the relative contributions of background selection and parallel selection to patterns of repeated differentiation, we examined 24 independently derived populations of freshwater stickleback occupying a variety of niches and estimated genomic patterns of differentiation in each relative to their common marine ancestor. Patterns of genetic differentiation were strongly correlated across pairs of freshwater populations adapting to the same ecological niche, supporting a role for parallel natural selection. In contrast to other recent work, our study comparing populations adapting to the same niche produced no evidence signifying that similar patterns of genomic differentiation are generated by background selection. We also found that overall patterns of genetic differentiation were considerably more similar for populations found in closer geographic proximity. In fact, the effect of geography on the repeatability of differentiation was greater than that of parallel selection. Our results suggest that shared selective landscapes and ancestral variation are the key drivers of repeated patterns of differentiation in systems that have recently colonized novel environments. More forthcoming papers &raquo; <p>Diana J. Rennison, Kira E. Delmore, Kieran Samuk, Gregory L. Owens, and Sara E. Miller (Feb 2020) </p> <p><b>Geographic proximity of populations strongly predicts magnitude of parallel genomic differentiation </b></p> <p><i><a href="https://dx.doi.org/10.1086/706476">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>losely related populations often display similar patterns of genomic differentiation, yet it remains an open question which ecological and evolutionary forces generate these patterns. The leading hypothesis is that this similarity in divergence is driven by parallel natural selection. However, several recent studies have suggested that these patterns may instead be a product of the depletion of genetic variation that occurs as result of background selection (i.e. linked negative selection). To date, there have been few direct tests of these competing hypotheses. To determine the relative contributions of background selection and parallel selection to patterns of repeated differentiation, we examined 24 independently derived populations of freshwater stickleback occupying a variety of niches and estimated genomic patterns of differentiation in each relative to their common marine ancestor. Patterns of genetic differentiation were strongly correlated across pairs of freshwater populations adapting to the same ecological niche, supporting a role for parallel natural selection. In contrast to other recent work, our study comparing populations adapting to the same niche produced no evidence signifying that similar patterns of genomic differentiation are generated by background selection. We also found that overall patterns of genetic differentiation were considerably more similar for populations found in closer geographic proximity. In fact, the effect of geography on the repeatability of differentiation was greater than that of parallel selection. Our results suggest that shared selective landscapes and ancestral variation are the key drivers of repeated patterns of differentiation in systems that have recently colonized novel environments. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Integrating fitness components reveals that survival costs outweigh other benefits and costs of group living in two closely related species” https://amnat.org/an/newpapers/Feb-Brouwer.html Lyanne Brouwer, Andrew Cockburn, and Martijn van de Pol (Feb 2020) Integrating fitness components reveals the importance of survival in shaping the costs and benefits of group living Read the Article (Just Accepted) Studies on group living animals have shown that living in groups maybe beneficial, for example because it increases foraging success, provides protection against predators, or even increases reproduction because group members assist in raising each other’s offspring. However, group living can also be costly because group members compete for food, space, or mating opportunities. Despite the enormous attention on the costs and benefits of group living, a limitation is that most studies have focused on a single cost or benefit—for example, the cost on survival or the benefit for reproduction. This means that it is unclear what the overall costs and benefits of group living are. In this study, Brouwer and collaborators investigate how six different fitness components vary with group size and subsequently integrate these to determine the overall costs and benefits of group living in two closely related fairy-wrens, family-living songbirds from Australia. They find that despite the differences between the species, the overall costs and benefits of group living are very similar, suggesting that the same behavioral mechanisms are important. For both species, the costs for additional group members on survival are most important for integrated fitness and this is amplified through carry-over effects of group size between years (i.e. large groups suffer survival costs, and are likely to do so the next year as well). In both species, integrated fitness of most group members was highest in small groups (size 2-3), and larger group sizes reduced fitness. How group size affects integrated fitness varied among different types of individuals, suggesting that group members potentially have a conflict of interest over optimal group size. This study provides a quantitative framework for future studies that aim to understand what demographic and behavioral mechanisms favor the evolution of cooperation or cause intra-group conflict. Abstract Group living can be beneficial when individuals reproduce or survive better in the presence of others, but simultaneously there might be costs due to competition for resources. Positive and negative effects on various fitness components might thus counteract each other, so integration is essential to determine their overall effect. Here, we investigated how an integrated fitness measure (reproductive values; RV) based on six fitness components varied with group size among group members in cooperatively-breeding red-winged and superb fairy-wrens (Malurus elegans and M.&nbsp;cyaneus). Despite life history differences between the species, patterns of RVs were similar, suggesting that the same behavioral mechanisms are important. Group living reduced RVs for dominant males, but for other group members this was only true in large groups. Decomposition analyses showed that our integrated fitness proxy was most strongly affected by group size effects on survival, which was amplified through carry-over effects between years. Our study shows that integrative consideration of fitness components and subsequent decomposition analysis provide much needed insights into the key behavioral mechanisms shaping the costs and benefits of group living. Such attribution is crucial if we are to synthesize the relative importance of the myriad group size costs and benefits currently reported in the literature. More forthcoming papers &raquo; <p>Lyanne Brouwer, Andrew Cockburn, and Martijn van de Pol (Feb 2020) </p> <p><b>Integrating fitness components reveals the importance of survival in shaping the costs and benefits of group living </b></p> <p><i><a href="https://dx.doi.org/10.1086/706475">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>tudies on group living animals have shown that living in groups maybe beneficial, for example because it increases foraging success, provides protection against predators, or even increases reproduction because group members assist in raising each other’s offspring. However, group living can also be costly because group members compete for food, space, or mating opportunities. Despite the enormous attention on the costs and benefits of group living, a limitation is that most studies have focused on a single cost or benefit&mdash;for example, the cost on survival or the benefit for reproduction. This means that it is unclear what the overall costs and benefits of group living are. In this study, Brouwer and collaborators investigate how six different fitness components vary with group size and subsequently integrate these to determine the overall costs and benefits of group living in two closely related fairy-wrens, family-living songbirds from Australia. </p><p>They find that despite the differences between the species, the overall costs and benefits of group living are very similar, suggesting that the same behavioral mechanisms are important. For both species, the costs for additional group members on survival are most important for integrated fitness and this is amplified through carry-over effects of group size between years (i.e. large groups suffer survival costs, and are likely to do so the next year as well). In both species, integrated fitness of most group members was highest in small groups (size 2-3), and larger group sizes reduced fitness. How group size affects integrated fitness varied among different types of individuals, suggesting that group members potentially have a conflict of interest over optimal group size. This study provides a quantitative framework for future studies that aim to understand what demographic and behavioral mechanisms favor the evolution of cooperation or cause intra-group conflict.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>roup living can be beneficial when individuals reproduce or survive better in the presence of others, but simultaneously there might be costs due to competition for resources. Positive and negative effects on various fitness components might thus counteract each other, so integration is essential to determine their overall effect. Here, we investigated how an integrated fitness measure (reproductive values; RV) based on six fitness components varied with group size among group members in cooperatively-breeding red-winged and superb fairy-wrens (<i>Malurus elegans</i> and <i>M.&nbsp;cyaneus</i>). Despite life history differences between the species, patterns of RVs were similar, suggesting that the same behavioral mechanisms are important. Group living reduced RVs for dominant males, but for other group members this was only true in large groups. Decomposition analyses showed that our integrated fitness proxy was most strongly affected by group size effects on survival, which was amplified through carry-over effects between years. Our study shows that integrative consideration of fitness components and subsequent decomposition analysis provide much needed insights into the key behavioral mechanisms shaping the costs and benefits of group living. Such attribution is crucial if we are to synthesize the relative importance of the myriad group size costs and benefits currently reported in the literature. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “The evolution of immigration strategies facilitates niche expansion by divergent adaptation in a structured metapopulation model” https://amnat.org/an/newpapers/Jan-Kisdi.html Éva Kisdi, Helene C. Weigang, and Mats Gyllenberg (Jan 2020) The evolution of immigration strategies facilitates niche expansion by divergent adaptation in a metapopulation model Read the Article (Just Accepted) Via Darwinian evolution, organisms adapt to the habitats where they live. Yet once adapted to a particular set of environmental conditions, it is pretty hard to broaden this "niche" of environments where the organism thrives, because adapting to a new environment usually comes at the cost of diminishing success in the old habitat. Since most individuals survive and reproduce in the old habitat, sacrificing reproduction in this habitat is too high a price for improving the chances of the few who wither in the new habitat. As a result, no change occurs and the niche is conserved. Many animals are able to choose actively where they live. Habitat choice appears to aggravate niche conservatism; as individuals choose favorable environments to which they are already adapted, they will not be exposed to new habitats. When not exposed to new habitats, there is no need to adapt to them. Live where you succeed, then there is no need to change how you live. This vicious circle can however be broken. The model of Kisdi et al. highlights the range of habitats that are marginally favorable, i.e., favorable if empty but unfavorable if crowded. In these habitats, a delicate balance evolves, where the local population size is just on the edge between making the habitat favorable or unfavorable. Once two strains of the organism are present (representing a minimum of genetic variability), this delicate balance is upset. No matter how little is the initial difference between the strains, each marginal habitat will be preferentially used by the strain that is better adapted there. With the two strains using different habitats, they start to adapt to different environmental conditions, which drives their habitat preferences further apart. As a result, the niche expands. Abstract Local adaptation and habitat choice are two key factors that control the distribution and diversification of species. Here we model habitat choice mechanistically as the outcome of dispersal with non-random immigration. We consider a structured metapopulation with a continuous distribution of patch types, and determine the evolutionarily stable immigration strategy as the function linking patch type to the probability of settling in the patch upon encounter. We uncover a novel mechanism whereby coexisting strains that only slightly differ in their local adaptation trait can evolve substantially different immigration strategies. In turn, different habitat use selects for divergent adaptations in the two strains. We propose that the joint evolution of immigration and local adaptation can facilitate diversification, and discuss our results in the light of niche conservatism versus niche expansion. More forthcoming papers &raquo; <p>Éva Kisdi, Helene C. Weigang, and Mats Gyllenberg (Jan 2020) </p> <p><b>The evolution of immigration strategies facilitates niche expansion by divergent adaptation in a metapopulation model </b></p> <p><i><a href="https://dx.doi.org/10.1086/706258">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">V</span>ia Darwinian evolution, organisms adapt to the habitats where they live. Yet once adapted to a particular set of environmental conditions, it is pretty hard to broaden this "niche" of environments where the organism thrives, because adapting to a new environment usually comes at the cost of diminishing success in the old habitat. Since most individuals survive and reproduce in the old habitat, sacrificing reproduction in this habitat is too high a price for improving the chances of the few who wither in the new habitat. As a result, no change occurs and the niche is conserved. </p><p>Many animals are able to choose actively where they live. Habitat choice appears to aggravate niche conservatism; as individuals choose favorable environments to which they are already adapted, they will not be exposed to new habitats. When not exposed to new habitats, there is no need to adapt to them. Live where you succeed, then there is no need to change how you live. </p><p>This vicious circle can however be broken. The model of Kisdi et al. highlights the range of habitats that are marginally favorable, i.e., favorable if empty but unfavorable if crowded. In these habitats, a delicate balance evolves, where the local population size is just on the edge between making the habitat favorable or unfavorable. Once two strains of the organism are present (representing a minimum of genetic variability), this delicate balance is upset. No matter how little is the initial difference between the strains, each marginal habitat will be preferentially used by the strain that is better adapted there. With the two strains using different habitats, they start to adapt to different environmental conditions, which drives their habitat preferences further apart. As a result, the niche expands. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>ocal adaptation and habitat choice are two key factors that control the distribution and diversification of species. Here we model habitat choice mechanistically as the outcome of dispersal with non-random immigration. We consider a structured metapopulation with a continuous distribution of patch types, and determine the evolutionarily stable immigration strategy as the function linking patch type to the probability of settling in the patch upon encounter. We uncover a novel mechanism whereby coexisting strains that only slightly differ in their local adaptation trait can evolve substantially different immigration strategies. In turn, different habitat use selects for divergent adaptations in the two strains. We propose that the joint evolution of immigration and local adaptation can facilitate diversification, and discuss our results in the light of niche conservatism versus niche expansion. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Community assembly and climate mismatch in Late-Quaternary eastern North American pollen assemblages” https://amnat.org/an/newpapers/Feb-Knight.html Clarke Knight, Jessica L. Blois, Benjamin Blonder, Marc Macias-Fauria, Alejandro Ordonez, and Jens-Christian Svenning (Feb 2020) Plot twist! Over 21 ka, climate-assemblage mismatch increased during fast climate shifts and in high-latitude/tree-dominated areas Read the Article (Just Accepted)What can the last 21 millennia in North America tell us about our future? Modern community ecology, which focuses on the here and now, is often disconnected from historical perspectives. However, important ecological processes – like vegetation response to climate change – manifest over a range of timespans, from decades to centuries, and millennia to deep-time. If the empirical richness of historical data could be more routinely applied to modern ecological concepts, ecologists could help forecast vegetation survival and persistence under future climate scenarios, as well as provide temporal context for modern concerns in community ecology. “We know that rapid environmental change defines our current world,” said lead author Clarke Knight, a PhD candidate at UC Berkeley in environmental science, “but by leveraging paleo data we can better understand past analogues that are applicable to modern situations.”Knight teamed up with researchers from UC Merced, the University of Oxford, and Aarhus University to look at vegetation change in North America over the last 21,000 years using a large, publicly-available fossil pollen dataset. They investigated how well plant communities kept pace with climatic changes and if certain community qualities (like the amount of trees) could predict the level of matching with the past climate. They found, for example, that tree-dominated, high-latitude communities were often out of step with climate. Such findings help constrain predictions for community response to future climate change. And, more broadly, by working at the edges of modern and paleo sciences, researchers can utilize history and advance the science of&nbsp;ecology. Abstract Plant community response to climate change ranges from synchronous tracking to strong mismatch. Explaining this variation in climate change response is critical for accurate global change modeling. Here we quantify how closely assemblages track changes in climate (match/mismatch) and how broadly climate niches are spread within assemblages (narrow/broad ecological tolerance, or ‘filtering’) using data for the last 21 ka for 531 eastern North American fossil pollen assemblages. Although climate matching has been strong over the last 21 millennia, mismatch increased in 30% of assemblages during the rapid climate shifts between 14.5 to 10 ka BP. Assemblage matching rebounded towards the present day in 10-20% of assemblages. Climate-assemblage mismatch was greater in tree-dominated and high-latitude assemblages, consistent with persisting populations, slower dispersal rates, and glacial retreat. In contrast, climate matching was greater for assemblages comprising taxa with higher median seed mass. Over half of the assemblages were climatically filtered at any given time, with peak filtering occurring at 8.5 ka BP for nearly 80% of assemblages. Thus, vegetation assemblages have highly variable rates of climate mismatch and filtering over millennial scales. These climate responses can be partially predicted by species’ traits and life histories. These findings help constrain predictions for plant community response to contemporary climate change. More forthcoming papers &raquo; <p>Clarke Knight, Jessica L. Blois, Benjamin Blonder, Marc Macias-Fauria, Alejandro Ordonez, and Jens-Christian Svenning (Feb 2020)</p> <p><b>Plot twist! Over 21 ka, climate-assemblage mismatch increased during fast climate shifts and in high-latitude/tree-dominated areas </b></p> <p><i><a href="https://dx.doi.org/10.1086/706340">Read the Article</a></i> (Just Accepted)</p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">W</span>hat can the last 21 millennia in North America tell us about our future? Modern community ecology, which focuses on the here and now, is often disconnected from historical perspectives. However, important ecological processes &ndash; like vegetation response to climate change &ndash; manifest over a range of timespans, from decades to centuries, and millennia to deep-time. If the empirical richness of historical data could be more routinely applied to modern ecological concepts, ecologists could help forecast vegetation survival and persistence under future climate scenarios, as well as provide temporal context for modern concerns in community ecology. &ldquo;We know that rapid environmental change defines our current world,&rdquo; said lead author Clarke Knight, a PhD candidate at UC Berkeley in environmental science, &ldquo;but by leveraging paleo data we can better understand past analogues that are applicable to modern situations.&rdquo;</p><p>Knight teamed up with researchers from UC Merced, the University of Oxford, and Aarhus University to look at vegetation change in North America over the last 21,000 years using a large, publicly-available fossil pollen dataset. They investigated how well plant communities kept pace with climatic changes and if certain community qualities (like the amount of trees) could predict the level of matching with the past climate. They found, for example, that tree-dominated, high-latitude communities were often out of step with climate. Such findings help constrain predictions for community response to future climate change. And, more broadly, by working at the edges of modern and paleo sciences, researchers can utilize history and advance the science of&nbsp;ecology.</p> <hr /><h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>lant community response to climate change ranges from synchronous tracking to strong mismatch. Explaining this variation in climate change response is critical for accurate global change modeling. Here we quantify how closely assemblages track changes in climate (match/mismatch) and how broadly climate niches are spread within assemblages (narrow/broad ecological tolerance, or &lsquo;filtering&rsquo;) using data for the last 21 ka for 531 eastern North American fossil pollen assemblages. Although climate matching has been strong over the last 21 millennia, mismatch increased in 30% of assemblages during the rapid climate shifts between 14.5 to 10 ka BP. Assemblage matching rebounded towards the present day in 10-20% of assemblages. Climate-assemblage mismatch was greater in tree-dominated and high-latitude assemblages, consistent with persisting populations, slower dispersal rates, and glacial retreat. In contrast, climate matching was greater for assemblages comprising taxa with higher median seed mass. Over half of the assemblages were climatically filtered at any given time, with peak filtering occurring at 8.5 ka BP for nearly 80% of assemblages. Thus, vegetation assemblages have highly variable rates of climate mismatch and filtering over millennial scales. These climate responses can be partially predicted by species&rsquo; traits and life histories. These findings help constrain predictions for plant community response to contemporary climate change.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Beyond Brownian motion and the Ornstein-Uhlenbeck process: Stochastic diffusion models for the evolution of quantitative characters” https://amnat.org/an/newpapers/Feb-Blomberg.html Simone P. Blomberg, Suren I. Rathnayake, and Cheyenne M. Moreau (Feb 2020) New evolutionary models for continuous traits, with an R package! Diffusion models get a closer evolutionary examination Read the Article (Just Accepted) Consider the way population geneticists model the evolution of gene frequencies over time, or the way quantitative genetic models are used for the understanding of trait evolution in response to natural selection. The evolutionary history of organisms does not enter into the mathematical equations describing the evolution of genes or traits. The models are “ahistorical” and hence are termed “microevolutionary” models: models that describe the evolution of traits (or genes) over short time scales. In contrast, a key principle of “macroevolutionary” models is that history matters. We cannot truly comprehend the evolution of traits without an understanding of the context of trait evolution gained by comparing multiple species over “deep time” using the so-called “comparative method.” Biologists who are interested in the evolution of quantitative traits (such as body mass, limb length, etc.) often wish to understand the tempo and mode of trait evolution over “deep time.” They ask questions such as, “Do some organisms evolve faster than others?”, “Has there been a shift in the mean value of a trait at some point in an organism’s evolutionary history?”, “How strong is natural selection in determining trait values?”, and “How are multiple traits related to each other and to the environment?” One way that biologists attempt to answer these questions is to fit mathematical models to trait data which describe the way evolution unfolds over time and along an evolutionary tree. Such models are called “diffusions,” as they model the path of a trait through evolutionary time as if it were a particle diffusing through a medium, being affected by both deterministic and stochastic forces. Most current diffusion models of evolution are designed for traits that follow the Normal distribution: the bell-shaped curve. In a new paper in The&nbsp;American Naturalist, a team from the University of Queensland in Australia, led by Dr. Simone Blomberg, describe two new models of trait evolution that do not require the traits to be described by a bell curve. These new models allow the study of quantitative traits that are not easily examined using current methods, such as lifespan or sex ratio. Using methods first developed for use in physics and quantitative finance, the team also demonstrate how to derive new, different models of evolution, how to understand their properties, and how to fit them to trait data on an evolutionary tree. They provide software tools to do this, using modern computer-intensive statistical techniques. The UQ team hope their new paper in The&nbsp;American Naturalist will inspire biologists to become more adventurous in modelling trait data over “deep time” and throw off the shackles of the Normal distribution! Abstract Gaussian processes such as Brownian motion and the Ornstein-Uhlenbeck process have been popular models for the evolution of quantitative traits and are widely used in phylogenetic comparative methods. However, they have drawbacks which limit their utility. Here we describe new, non-Gaussian stochastic differential equation (diffusion) models of quantitative trait evolution. We present general methods for deriving new diffusion models, and develop new software for fitting non-Gaussian evolutionary models to trait data. The theory of stochastic processes provides a mathematical framework for understanding the properties of current and future phylogenetic comparative methods. Attention to the mathematical details of models of trait evolution and diversification may help avoid some pitfalls when using stochastic processes to model macroevolution. More forthcoming papers &raquo; <p>Simone P. Blomberg, Suren I. Rathnayake, and Cheyenne M. Moreau (Feb 2020) </p> <p><b>New evolutionary models for continuous traits, with an R package! Diffusion models get a closer evolutionary examination </b></p> <p><i><a href="https://dx.doi.org/10.1086/706339">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsider the way population geneticists model the evolution of gene frequencies over time, or the way quantitative genetic models are used for the understanding of trait evolution in response to natural selection. The evolutionary history of organisms does not enter into the mathematical equations describing the evolution of genes or traits. The models are “ahistorical” and hence are termed “microevolutionary” models: models that describe the evolution of traits (or genes) over short time scales. In contrast, a key principle of “macroevolutionary” models is that history matters. We cannot truly comprehend the evolution of traits without an understanding of the context of trait evolution gained by comparing multiple species over “deep time” using the so-called “comparative method.” </p><p>Biologists who are interested in the evolution of quantitative traits (such as body mass, limb length, etc.) often wish to understand the tempo and mode of trait evolution over “deep time.” They ask questions such as, “Do some organisms evolve faster than others?”, “Has there been a shift in the mean value of a trait at some point in an organism’s evolutionary history?”, “How strong is natural selection in determining trait values?”, and “How are multiple traits related to each other and to the environment?” One way that biologists attempt to answer these questions is to fit mathematical models to trait data which describe the way evolution unfolds over time and along an evolutionary tree. Such models are called “diffusions,” as they model the path of a trait through evolutionary time as if it were a particle diffusing through a medium, being affected by both deterministic and stochastic forces. </p><p>Most current diffusion models of evolution are designed for traits that follow the Normal distribution: the bell-shaped curve. In a new paper in <i>The&nbsp;American Naturalist</i>, a team from the University of Queensland in Australia, led by Dr. Simone Blomberg, describe two new models of trait evolution that do not require the traits to be described by a bell curve. These new models allow the study of quantitative traits that are not easily examined using current methods, such as lifespan or sex ratio. Using methods first developed for use in physics and quantitative finance, the team also demonstrate how to derive new, different models of evolution, how to understand their properties, and how to fit them to trait data on an evolutionary tree. They provide software tools to do this, using modern computer-intensive statistical techniques. </p><p>The UQ team hope their new paper in <i>The&nbsp;American Naturalist</i> will inspire biologists to become more adventurous in modelling trait data over “deep time” and throw off the shackles of the Normal distribution! </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>aussian processes such as Brownian motion and the Ornstein-Uhlenbeck process have been popular models for the evolution of quantitative traits and are widely used in phylogenetic comparative methods. However, they have drawbacks which limit their utility. Here we describe new, non-Gaussian stochastic differential equation (diffusion) models of quantitative trait evolution. We present general methods for deriving new diffusion models, and develop new software for fitting non-Gaussian evolutionary models to trait data. The theory of stochastic processes provides a mathematical framework for understanding the properties of current and future phylogenetic comparative methods. Attention to the mathematical details of models of trait evolution and diversification may help avoid some pitfalls when using stochastic processes to model macroevolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT Applications for the 2020 ASN Jasper Loftus-Hills Young Investigator’s Awards https://amnat.org/announcements/NomYIAforms.html &nbsp; The Jasper Loftus-Hill Young Investigator’s Award of the American Society of Naturalists honors outstanding promise and accomplishments of young investigators who conduct integrative work in the fields of Ecology, Evolutionary Biology, Behavioral Ecology, and Genetics. Applicants working in any of these fields are encouraged to apply. The award honors outstanding promise and accomplishments of young investigators (3 years post-Ph.D., or in the final year of their Ph.D) who conduct integrative work in ecology, evolution, behavioral ecology, and genetics (see * below) . The award was established in 1984 to recognize exceptional work by investigators who received their doctorates in the three years preceding the application deadline, or who are in their final year of graduate school. The award commemorates Jasper Loftus-Hills (1946-1974), an Australian biologist of exceptional promise who died tragically during the course of fieldwork three years after receiving his degree. Winners of this award will present a research paper in the Young Investigator’s Symposium at the ASN annual meeting and receive a $500 prize, a travel allowance of $700, cost of registration for the meetings, and a supplement of $500 in case of intercontinental travel. Four awards are made annually. Recipients need not be members of the Society. In order to apply for this award, applicants should go to this link to the Google form, where they will be asked to answer a few questions and upload their application (see ** below). The application should consist of one pdf, with the following (in this exact order): - CV (no page limit) - Research statement (3 page limit, including figures) - 3 reprints Additionally, two letters by individuals familiar with the applicant’s work should be uploaded by referees to the following link to a Google form.&nbsp;(see ** below).&nbsp; Applicants are responsible for ensuring their letter writers submit their letters before the deadline (this can be done before submitting an application), as applications will not be considered complete without these two letters. &nbsp; *Time since PhD degree can be extended by 1 year for each child born or adopted during this period if the applicant was a primary care giver. Other forms of exceptional care giving responsibility (e.g. partner, spouse, aged parent, etc.) will be considered on a case-by-case basis. **Applicants and letter writers will be required to sign into an account registered with Google to upload their applications and letters, respectively. Please contact Renee Duckworth (rad3@email.arizona.edu) and / or Janneke Hille Ris Lambers (jhrl@uw.edu) for an alternative approach if that is not possible. &nbsp;Jasper Loftus-Hills (1946-1974) was an Australian biologist of exceptional promise who lost his life doing fieldwork recording frog calls in Texas, three years after receiving his degree from the University of Melbourne. An obituary appeared in Copeia in 1974 (Alexander, Richard D. "Jasper Loftus-Hills." Copeia 1974:812-13). The Golden Coqu&iacute; (in the photo above) was discovered on Puerto Rico by George E. Drewry, Kirkland L. Jones, Julia R. Clark, and Jasper J. Loftus-Hills. They had planned to name the species for its color, but when Loftus-Hills was killed in 1974, his colleagues chose instead to name it in his honor: A further description of Jasper Loftus-Hills appeared in Copeia 2015 (103:467-475), which is a retrospective on his mentor, Murray John Littlejohn (doi:&nbsp;http://dx.doi.org/10.1643/OT-15-274) The most gifted graduate student Murray ever worked with (in his own estimation) was Jasper Loftus-Hills, whose Ph.D. thesis “Auditory function and acoustic communication in anuran amphibians” was completed in 1971. Jasper followed in Murray’s footsteps to Austin and then went on to Cornell University and the University of Michigan. He was tragically killed by a hit-and-run driver while doing night fieldwork on Gastrophryne in Texas in 1974. The 1992 Gastrophryne paper coauthored by Jasper and Murray is a lucid analysis of the state of the art in character displacement and reinforcement, two terms burdened with a long history of confusion. (Loftus-Hills, J. J., and M. J. Littlejohn.&nbsp;1992.&nbsp;Reinforcement and reproductive character displacement inGastrophryne carolinensis&nbsp;and&nbsp;G. olivacea&nbsp;(Anura: Microhylidae): a re-evaluation.&nbsp;Evolution 46:896–906.) &nbsp; <p>&nbsp;</p> <p>The Jasper Loftus-Hill Young Investigator&rsquo;s Award of the American Society of Naturalists honors outstanding promise and accomplishments of young investigators who conduct integrative work in the fields of Ecology, Evolutionary Biology, Behavioral Ecology, and Genetics. Applicants working in any of these fields are encouraged to apply.</p> <p>The award honors outstanding promise and accomplishments of young investigators (3 years post-Ph.D., or in the final year of their Ph.D) who conduct integrative work in ecology, evolution, behavioral ecology, and genetics <strong><a href="#time">(see * below</a></strong>) . The award was established in 1984 to recognize exceptional work by investigators who received their doctorates in the three years preceding the application deadline, or who are in their final year of graduate school. The award commemorates Jasper Loftus-Hills (1946-1974), an Australian biologist of exceptional promise who died tragically during the course of fieldwork three years after receiving his degree.</p> <p>Winners of this award will present a research paper in the Young Investigator&rsquo;s Symposium at the ASN annual meeting and receive a $500 prize, a travel allowance of $700, cost of registration for the meetings, and a supplement of $500 in case of intercontinental travel. Four awards are made annually. Recipients need not be members of the Society.</p> <p>In order to apply for this award, applicants should go to this<span style="font-size:11.0pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"> <a href="https://forms.gle/QyC99nAJb7HE42KS8" style="color:blue; text-decoration:underline">link</a> to the Google form, </span></span>where they will be asked to answer a few questions and upload their application <span style="font-size:11.0pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><a href="#time">(<strong>see ** below</strong>)</a></span></span>. The application should consist of one pdf, with the following (in this exact order):<br /> - CV (no page limit)<br /> - Research statement (3 page limit, including figures)<br /> - 3 reprints</p> <p>Additionally, two letters by individuals familiar with the applicant&rsquo;s work should be uploaded by referees <span style="font-size:11.0pt"><span style="font-family:&quot;Calibri&quot;,sans-serif">to the following <a href="https://forms.gle/DcSjx34MasjwPGZe7" style="color:blue; text-decoration:underline">link</a> to a Google form.&nbsp;<a href="#time">(<strong>see ** below</strong>)</a>.&nbsp; </span></span>Applicants are responsible for ensuring their letter writers submit their letters before the deadline (this can be done before submitting an application), as applications will not be considered complete without these two letters.</p> <p>&nbsp;</p> <p id="time">*<strong>Time since PhD degree</strong> can be extended by 1 year for each child born or adopted during this period if the applicant was a primary care giver. Other forms of exceptional care giving responsibility (e.g. partner, spouse, aged parent, etc.) will be considered on a case-by-case basis.</p> <p>**<strong>Applicants and letter writers will be required to sign into an account registered with Google</strong> to upload their applications and letters, respectively. Please contact Renee Duckworth (<a href="mailto:rad3@email.arizona.edu">rad3@email.arizona.edu</a>) and / or Janneke Hille Ris Lambers (<a href="mailto:jhrl@uw.edu">jhrl@uw.edu</a>) for an alternative approach if that is not possible.</p> <p>&nbsp;</p><p>Jasper Loftus-Hills (1946-1974) was an Australian biologist of exceptional promise who lost his life doing fieldwork recording frog calls in Texas, three years after receiving his degree from the University of Melbourne. <a href="/dam/jcr:50a091cd-227f-4bff-9f60-687a6679b1d8/JLH%20obituary.pdf">An obituary appeared in <i>Copeia</i></a> in 1974 (Alexander, Richard D. &quot;Jasper Loftus-Hills.&quot; <em>Copeia</em> 1974:812-13).</p> <p>The Golden Coqu&iacute; (in the photo above) was discovered on Puerto Rico by George E. Drewry, Kirkland L. Jones, Julia R. Clark, and Jasper J. Loftus-Hills. They had planned to name the species for its color, but when Loftus-Hills was killed in 1974, his colleagues chose instead to name it in his honor:</p> <p>A further description of Jasper Loftus-Hills appeared in <i>Copeia</i> 2015 (103:467-475), which is a retrospective on his mentor, Murray John Littlejohn (doi:&nbsp;<a href="http://dx.doi.org/10.1643/OT-15-274">http://dx.doi.org/10.1643/OT-15-274</a>)</p> <blockquote>The most gifted graduate student Murray ever worked with (in his own estimation) was Jasper Loftus-Hills, whose Ph.D. thesis &ldquo;Auditory function and acoustic communication in anuran amphibians&rdquo; was completed in 1971. Jasper followed in Murray&rsquo;s footsteps to Austin and then went on to Cornell University and the University of Michigan. He was tragically killed by a hit-and-run driver while doing night fieldwork on Gastrophryne in Texas in 1974. The 1992 Gastrophryne paper coauthored by Jasper and Murray is a lucid analysis of the state of the art in character displacement and reinforcement, two terms burdened with a long history of confusion.<br /> (<span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">Loftus-Hills, J. J., and M. J. Littlejohn.&nbsp;</span><span class="NLM_year" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">1992</span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">.&nbsp;</span><span class="NLM_article-title" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">Reinforcement and reproductive character displacement in<i>Gastrophryne carolinensis</i>&nbsp;and&nbsp;<i>G. olivacea</i>&nbsp;(Anura: Microhylidae): a re-evaluation</span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">.&nbsp;</span><span class="citation_source-journal" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px; font-style: italic;">Evolution </span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">46:</span><span class="NLM_fpage" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">896</span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">&ndash;</span><span class="NLM_lpage" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">906</span><span class="citation_source-journal" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px; font-style: italic;">.</span>)</blockquote> <p>&nbsp;</p> Tue, 01 Oct 2019 05:00:00 GMT “Gliding dragons and flying squirrels: diversifying versus stabilizing selection on morphology following the evolution of an innovation” https://amnat.org/an/newpapers/Feb-Ord.html Terry J. Ord, Joan Garcia-Porta, Marina Querejeta, and David C. Collar (Feb 2020) UNSW researchers show gliding animals are an evolutionary surprise because their innovation did not lead to a proliferation of new adaptive forms Read the Article (Just Accepted) A&nbsp;study of gliding animals has challenged the idea that evolutionary innovations – adaptations that bring new abilities and advantages – spur the origin of other new body types and other characteristics in descendent species. The research, undertaken by evolutionary biologists at UNSW Sydney and universities in the US and Spain, examined the key innovation of gliding in two types of gliding animals: ‘flying’ dragons (family Agamidae) and ‘flying’ squirrels (family Sciuridae), both common to forests in Southeast Asia. The study confirms previous assumptions that gliding animals originated from arboreal ancestors and likely arose as a means of escaping predators some 25-30 million years ago. Lead author Dr. Terry Ord, an evolutionary ecologist with UNSW’s Evolution & Ecology Research Centre, says another advantage that gliding brought was the ability to exploit a new three dimensional environment and explore more of the forest than just one tree. “From an evolutionary biologist’s perspective, these types of innovation that open up new opportunities are assumed to drive even more adapted diversification,” Dr. Ord says. “Suddenly there’s all these new microhabitats available offering up new resources and you have new species moving into those particular microhabitats where you would expect them to adapt even more.” The evolution of flight in birds, insects and bats is an example where the changes brought about by ‘taking to the wing’ caused an explosion in diversity. Millions of species of insects, tens of thousands of birds and more than a thousand species of bats developed greatly different shapes, sizes, behaviors and habitats since their ancestors first evolved to fly. But in the case of the gliding animals like the dragons and squirrels, the advantage of gliding has not led to a proliferation of changes to body shapes, sizes and functions. In fact, for the dragons the key innovation of gliding appears to have done the opposite. “In the case of the dragon lizards, gliding appears to be a constraint on subsequent adaptation because of the aerodynamics of having to glide,” Dr. Ord says. “Basically the heavier you are, the more difficult it is to glide. So there is a constraint on general body size and shape – meaning a halt to the evolution of longer limbs and bigger heads, for example, that would normally reflect adaptation to particular microhabitats. But instead, the dragons have to glide, and that means limiting their body sizes to stay small and aerodynamic – which has what we call stabilizing selection on their bodies.” Interestingly, some species of flying dragons actually did go on to evolve larger bodies, at the expense of their gliding abilities. To offset their poor gliding, they had to develop new behaviors such as flattening their bodies against the tree trunk to blend in with the bark, Dr. Ord says. “So they’re almost regressing from that gliding lifestyle. But in this case, the reason why they’re changing their body size is to overcome competition with other lizards.” There were no such bodily constraints with squirrels, due to key differences in the gliding membranes. Whereas the ribs of the dragon lizards evolved to extend laterally as the ‘wings’ of the animals, the squirrels’ gliding membrane developed as a flap of skin joining their wrists to their ankles. “So squirrels just evolve longer limbs which means the size of the membrane increases proportionally to the longer limbs, enabling somewhat bigger bodied animals to glide without sacrificing too much ability,” says Dr. Ord. But despite squirrel body sizes not being as constrained, the body sizes and characteristics of gliding squirrels are no more diverse than non-gliding squirrels. “So again the expectation of a key innovation driving the evolution of greater diversity was thwarted in the case of gliding squirrels.” Dr. Ord says his research has implications for our understanding of the way key innovations and competition come into play in evolution. “Evolutionary innovations are evocative because they’re often amazing curiosities. And perhaps this has led us to infer they’re also key in opening the door to even more adaptation. But it seems that interactions with other organisms – competition for resources – is a far more powerful force for generating adaptive diversity,” he says. Looking ahead, Dr. Ord will be following up with research into the dragon lizards to find out how they use another evolutionary innovation, their dewlaps – the colorful flap of skin that hangs beneath their jaws – to communicate. Abstract Evolutionary innovations and ecological competition are factors often cited as drivers of adaptive diversification. Yet many innovations result in stabilizing rather than diversifying selection on morphology, and morphological disparity among co-existing species can reflect competitive exclusion (species sorting) rather than sympatric adaptive divergence (character displacement). We studied the innovation of gliding in dragons (Agamidae) and squirrels (Sciuridae) and its effect on subsequent body size diversification. We found gliding either had no impact (squirrels) or resulted in strong stabilizing selection on body size (dragons). Despite this constraining effect in dragons, sympatric gliders exhibit greater size disparity compared to allopatric gliders, a pattern consistent with, though not exclusively explained by, ecological competition changing the adaptive landscape of body size evolution to induce character displacement. These results show that innovations do not necessarily instigate further differentiation among species as so often assumed, and suggest competition can be a powerful force generating morphological divergence among co-existing species, even in the face of strong stabilizing selection. More forthcoming papers &raquo; <p>Terry J. Ord, Joan Garcia-Porta, Marina Querejeta, and David C. Collar (Feb 2020) </p> <p><b>UNSW researchers show gliding animals are an evolutionary surprise because their innovation did not lead to a proliferation of new adaptive forms </b></p><p><i><a href="https://dx.doi.org/10.1086/706305">Read the Article</a></i> (Just Accepted) </p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>&nbsp;study of gliding animals has challenged the idea that evolutionary innovations &ndash; adaptations that bring new abilities and advantages &ndash; spur the origin of other new body types and other characteristics in descendent species. The research, undertaken by evolutionary biologists at UNSW Sydney and universities in the US and Spain, examined the key innovation of gliding in two types of gliding animals: &lsquo;flying&rsquo; dragons (family Agamidae) and &lsquo;flying&rsquo; squirrels (family Sciuridae), both common to forests in Southeast Asia. The study confirms previous assumptions that gliding animals originated from arboreal ancestors and likely arose as a means of escaping predators some 25-30 million years ago.</p> <p>Lead author Dr. Terry Ord, an evolutionary ecologist with UNSW&rsquo;s Evolution &amp; Ecology Research Centre, says another advantage that gliding brought was the ability to exploit a new three dimensional environment and explore more of the forest than just one tree. &ldquo;From an evolutionary biologist&rsquo;s perspective, these types of innovation that open up new opportunities are assumed to drive even more adapted diversification,&rdquo; Dr. Ord says. &ldquo;Suddenly there&rsquo;s all these new microhabitats available offering up new resources and you have new species moving into those particular microhabitats where you would expect them to adapt even more.&rdquo;</p> <p>The evolution of flight in birds, insects and bats is an example where the changes brought about by &lsquo;taking to the wing&rsquo; caused an explosion in diversity. Millions of species of insects, tens of thousands of birds and more than a thousand species of bats developed greatly different shapes, sizes, behaviors and habitats since their ancestors first evolved to fly. But in the case of the gliding animals like the dragons and squirrels, the advantage of gliding has not led to a proliferation of changes to body shapes, sizes and functions. In fact, for the dragons the key innovation of gliding appears to have done the opposite. &ldquo;In the case of the dragon lizards, gliding appears to be a constraint on subsequent adaptation because of the aerodynamics of having to glide,&rdquo; Dr. Ord says. &ldquo;Basically the heavier you are, the more difficult it is to glide. So there is a constraint on general body size and shape &ndash; meaning a halt to the evolution of longer limbs and bigger heads, for example, that would normally reflect adaptation to particular microhabitats. But instead, the dragons have to glide, and that means limiting their body sizes to stay small and aerodynamic &ndash; which has what we call stabilizing selection on their bodies.&rdquo;</p> <p>Interestingly, some species of flying dragons actually did go on to evolve larger bodies, at the expense of their gliding abilities. To offset their poor gliding, they had to develop new behaviors such as flattening their bodies against the tree trunk to blend in with the bark, Dr. Ord says. &ldquo;So they&rsquo;re almost regressing from that gliding lifestyle. But in this case, the reason why they&rsquo;re changing their body size is to overcome competition with other lizards.&rdquo; There were no such bodily constraints with squirrels, due to key differences in the gliding membranes. Whereas the ribs of the dragon lizards evolved to extend laterally as the &lsquo;wings&rsquo; of the animals, the squirrels&rsquo; gliding membrane developed as a flap of skin joining their wrists to their ankles. &ldquo;So squirrels just evolve longer limbs which means the size of the membrane increases proportionally to the longer limbs, enabling somewhat bigger bodied animals to glide without sacrificing too much ability,&rdquo; says Dr. Ord. But despite squirrel body sizes not being as constrained, the body sizes and characteristics of gliding squirrels are no more diverse than non-gliding squirrels. &ldquo;So again the expectation of a key innovation driving the evolution of greater diversity was thwarted in the case of gliding squirrels.&rdquo;</p> <p>Dr. Ord says his research has implications for our understanding of the way key innovations and competition come into play in evolution. &ldquo;Evolutionary innovations are evocative because they&rsquo;re often amazing curiosities. And perhaps this has led us to infer they&rsquo;re also key in opening the door to even more adaptation. But it seems that interactions with other organisms &ndash; competition for resources &ndash; is a far more powerful force for generating adaptive diversity,&rdquo; he says. Looking ahead, Dr. Ord will be following up with research into the dragon lizards to find out how they use another evolutionary innovation, their dewlaps &ndash; the colorful flap of skin that hangs beneath their jaws &ndash; to communicate.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">E</span>volutionary innovations and ecological competition are factors often cited as drivers of adaptive diversification. Yet many innovations result in stabilizing rather than diversifying selection on morphology, and morphological disparity among co-existing species can reflect competitive exclusion (species sorting) rather than sympatric adaptive divergence (character displacement). We studied the innovation of gliding in dragons (Agamidae) and squirrels (Sciuridae) and its effect on subsequent body size diversification. We found gliding either had no impact (squirrels) or resulted in strong stabilizing selection on body size (dragons). Despite this constraining effect in dragons, sympatric gliders exhibit greater size disparity compared to allopatric gliders, a pattern consistent with, though not exclusively explained by, ecological competition changing the adaptive landscape of body size evolution to induce character displacement. These results show that innovations do not necessarily instigate further differentiation among species as so often assumed, and suggest competition can be a powerful force generating morphological divergence among co-existing species, even in the face of strong stabilizing selection.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 23 Sep 2019 05:00:00 GMT “Matrix models unravel that decreased precipitation predictability negatively affects population growth through differences in adult survival” https://amnat.org/an/newpapers/Jan-Maso.html Guillem Masó, Arpat Ozgul, and Patrick S. Fitze (Jan 2020) Read the Article (Just Accepted) Climatic predictability: consistent small non-significant survival differences add up to important population decline Global climate change is exposing animal populations to novel conditions that might affect species persistence and increase their susceptibility to become extinct. Global climate change is known to affect average environmental conditions. For example, it leads to higher average temperatures and in some localities, it reduces precipitation. However, despite its effect on average conditions, it also affects environmental predictability (i.e. the correlation among measures of time series). For example, a decrease in precipitation predictability means that using precipitation falling today we can predict the likelihood that precipitation falls the next day, and this likelihood is smaller when predicting the next day’s precipitation in one month. While most studies tackle the effects of differences in average conditions, hardly any studies investigated whether animal population are affected by changes in environmental predictability, and how they will respond. To understand whether and how changes in environmental predictability might affect species persistence, a research team from the Natural Museum of Natural Sciences in Madrid (MNCN-CSIC), the Pyrenean Institute of Ecology (IPE-CSIC), and the University of Z&uuml;rich (UZH) tested the effects of differences in precipitation predictability on the European common lizard (Zootoca vivipara, subspecies louislantzi). They exposed lizard populations to more and less predictable precipitation over three years, and measured the lizard’s survival and reproduction, the latter using molecular paternity assignment. Thereafter, they used complex statistical population models to test for effects of precipitation predictability on population dynamics and the mechanisms underlying these effects.How do populations respond to differences in environmental predictability? The team found that reduced precipitation predictability negatively affected population growth, which leads to a decrease in population size and increased extinction risk. Which mechanisms are underlying this population decline? The study demonstrated that the prime suspect parameters (e.g. effects on reproduction) were not responsible for the observed decline. On the contrary, the team showed that small, but consistent differences in survival explained the negative effect on population growth. More specifically, mainly slight differences in adult survival, the least vulnerable age class, rather than survival of the competitively inferior yearlings and juveniles were responsible for the observed population decline. The study shows that changes in environmental predictability might have major consequences on population dynamics and that the decrease in an environment’s predictability forecasted by climatic models may exacerbate the rate of the massive population declines currently observed in lizards, amphibians, and birds. Finally, the study as well shows that despite these massive effects, their detection under field conditions requires decades of research, since only complex analyses based on sophisticated and tricky to get data, allow to unravel them over short time intervals. This may explain why in many cases population declines are detected late and not until they are massive, which importantly affects their conservation. Abstract Global climate change is leading to decreased climatic predictability. Theoretical work indicates that changes in the climate’s intrinsic predictability will affect population dynamics and extinction, but experimental evidence is scarce. Here, we experimentally tested whether differences in intrinsic precipitation predictability affect population dynamics of the European common lizard (Zootoca vivipara) by simulating more (MP) and less predictable (LP) precipitation in 12 semi-natural populations over 3 years and measuring different vital rates. A seasonal age-structured matrix model was parametrized to assess treatment effects on vital rates and asymptotic population growth (λ). There was a non-significant trend for survival being higher in MP than LP precipitation, and no differences existed in reproductive rates. Small non-significant survival differences in adults explained changes in λ and survival differences among age-classes were in line with predictions from cohort resonance. As a result, λ was significantly higher in MP than LP. This experimentally shows that small effects have major consequences on λ, that forecasted decreases in precipitation predictability are likely to exacerbate the current rate of population decline and extinction, and that stage-structured matrix models are required to unravel the aftermath of climate change. More forthcoming papers &raquo; <p>Guillem Masó, Arpat Ozgul, and Patrick S. Fitze (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706183">Read the Article</a></i> (Just Accepted) </p> <p><b>Climatic predictability: consistent small non-significant survival differences add up to important population decline </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>lobal climate change is exposing animal populations to novel conditions that might affect species persistence and increase their susceptibility to become extinct. Global climate change is known to affect average environmental conditions. For example, it leads to higher average temperatures and in some localities, it reduces precipitation. However, despite its effect on average conditions, it also affects environmental predictability (i.e. the correlation among measures of time series). For example, a decrease in precipitation predictability means that using precipitation falling today we can predict the likelihood that precipitation falls the next day, and this likelihood is smaller when predicting the next day&rsquo;s precipitation in one month. While most studies tackle the effects of differences in average conditions, hardly any studies investigated whether animal population are affected by changes in environmental predictability, and how they will respond.</p> <p>To understand whether and how changes in environmental predictability might affect species persistence, a research team from the Natural Museum of Natural Sciences in Madrid (MNCN-CSIC), the Pyrenean Institute of Ecology (IPE-CSIC), and the University of Z&uuml;rich (UZH) tested the effects of differences in precipitation predictability on the European common lizard (<i>Zootoca vivipara</i>, subspecies <i>louislantzi</i>). They exposed lizard populations to more and less predictable precipitation over three years, and measured the lizard&rsquo;s survival and reproduction, the latter using molecular paternity assignment. Thereafter, they used complex statistical population models to test for effects of precipitation predictability on population dynamics and the mechanisms underlying these effects.</p><p>How do populations respond to differences in environmental predictability? The team found that reduced precipitation predictability negatively affected population growth, which leads to a decrease in population size and increased extinction risk. </p><p>Which mechanisms are underlying this population decline? The study demonstrated that the prime suspect parameters (e.g. effects on reproduction) were not responsible for the observed decline. On the contrary, the team showed that small, but consistent differences in survival explained the negative effect on population growth. More specifically, mainly slight differences in adult survival, the least vulnerable age class, rather than survival of the competitively inferior yearlings and juveniles were responsible for the observed population decline. </p><p>The study shows that changes in environmental predictability might have major consequences on population dynamics and that the decrease in an environment’s predictability forecasted by climatic models may exacerbate the rate of the massive population declines currently observed in lizards, amphibians, and birds. Finally, the study as well shows that despite these massive effects, their detection under field conditions requires decades of research, since only complex analyses based on sophisticated and tricky to get data, allow to unravel them over short time intervals. This may explain why in many cases population declines are detected late and not until they are massive, which importantly affects their conservation.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>lobal climate change is leading to decreased climatic predictability. Theoretical work indicates that changes in the climate’s intrinsic predictability will affect population dynamics and extinction, but experimental evidence is scarce. Here, we experimentally tested whether differences in intrinsic precipitation predictability affect population dynamics of the European common lizard (<i>Zootoca vivipara</i>) by simulating more (MP) and less predictable (LP) precipitation in 12 semi-natural populations over 3 years and measuring different vital rates. A seasonal age-structured matrix model was parametrized to assess treatment effects on vital rates and asymptotic population growth (<i>λ</i>). There was a non-significant trend for survival being higher in MP than LP precipitation, and no differences existed in reproductive rates. Small non-significant survival differences in adults explained changes in λ and survival differences among age-classes were in line with predictions from cohort resonance. As a result, λ was significantly higher in MP than LP. This experimentally shows that small effects have major consequences on λ, that forecasted decreases in precipitation predictability are likely to exacerbate the current rate of population decline and extinction, and that stage-structured matrix models are required to unravel the aftermath of climate change. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 18 Sep 2019 05:00:00 GMT “Why do phytoplankton evolve large size in response to grazing?” https://amnat.org/an/newpapers/Jan-Branco.html Pedro Branco, Martijn Egas, Spencer R. Hall, and Jef Huisman (Jan 2020) Read the Article (Just Accepted) Why do phytoplankton evolve large size in response to grazing? A new explanation based on selection for nutritious food Phytoplankton are among the tiniest organisms on Earth. Yet they display wide variation in size, from small species less than a micrometer to large species of almost a millimeter. Small phytoplankton species tend to be better competitors for nutrients, whereas large phytoplankton may be more difficult to handle for grazing zooplankton. Hence, the evolution of large phytoplankton is often explained as a physical defense against grazing. A major difficulty with this explanation, however, is that zooplankton may counter this escape from grazing by coevolving to a large size as well. So why do phytoplankton evolve large size in response to grazing? Here, Pedro Branco, Martijn Egas, Spencer Hall and Jef Huisman propose a new explanation. They argue that a major evolutionary advantage for large phytoplankton is their low nutritional quality. To investigate this hypothesis, the authors develop a mathematical model in which the individual sizes of phytoplankton and zooplankton coevolve. The model makes two key assumptions supported by observational studies. First, the nutrient content of phytoplankton cells varies allometrically with cell size, such that large phytoplankton cells contain less nutrient per unit cell volume than small phytoplankton cells. Second, zooplankton can graze selectively, with a preference for nutritious food. Combining these two assumptions, the model predicts that selective grazing on small but nutritious food will favor evolution of large phytoplankton of low nutritional quality. Hence, a size-dependent change in food quality may explain why phytoplankton of large size often dominate in waters with high grazing pressure. Abstract Phytoplankton are among the smallest primary producers on Earth, and yet display a wide range of cell sizes. Typically, small phytoplankton species are stronger nutrient competitors than large phytoplankton species, but they are also more easily grazed. In contrast, evolution of large phytoplankton is often explained as a physical defense against grazing. Conceptually this explanation is problematic, however, because zooplankton can coevolve larger size to counter this size-dependent escape from grazing. Here, we hypothesize that there is another advantage for the evolution of large phytoplankton size not so readily overcome: larger phytoplankton often provide lower nutritional quality for zooplankton. We investigate this hypothesis by analyzing an eco-evolutionary model that combines the ecological stoichiometry of phytoplankton-zooplankton interactions with coevolution of phytoplankton and zooplankton size. In our model, evolution of cell size modifies the nutrient uptake kinetics of phytoplankton according to known allometric relationships, which in turn affect the nutritional quality of phytoplankton. With this size-based mechanism, the model predicts that low grazing pressure or nonselective grazing by zooplankton favors evolution of small phytoplankton cells of high nutritional quality. In contrast, selective grazing for nutritious food favors evolution of large phytoplankton of low nutritional quality, which are preyed upon by medium- to large-sized zooplankton. This size-dependent change in food quality may explain the commonly observed shift from dominance by small picophytoplankton in oligotrophic waters with low grazing pressure to large phytoplankton species in nutrient-rich waters with high grazing pressure. More forthcoming papers &raquo; <p>Pedro Branco, Martijn Egas, Spencer R. Hall, and Jef Huisman (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706251">Read the Article</a></i> (Just Accepted) </p> <p><b>Why do phytoplankton evolve large size in response to grazing? A new explanation based on selection for nutritious food </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>hytoplankton are among the tiniest organisms on Earth. Yet they display wide variation in size, from small species less than a micrometer to large species of almost a millimeter. Small phytoplankton species tend to be better competitors for nutrients, whereas large phytoplankton may be more difficult to handle for grazing zooplankton. Hence, the evolution of large phytoplankton is often explained as a physical defense against grazing. A major difficulty with this explanation, however, is that zooplankton may counter this escape from grazing by coevolving to a large size as well. So why <i>do</i> phytoplankton evolve large size in response to grazing? </p><p>Here, Pedro Branco, Martijn Egas, Spencer Hall and Jef Huisman propose a new explanation. They argue that a major evolutionary advantage for large phytoplankton is their low nutritional quality. To investigate this hypothesis, the authors develop a mathematical model in which the individual sizes of phytoplankton and zooplankton coevolve. The model makes two key assumptions supported by observational studies. First, the nutrient content of phytoplankton cells varies allometrically with cell size, such that large phytoplankton cells contain less nutrient per unit cell volume than small phytoplankton cells. Second, zooplankton can graze selectively, with a preference for nutritious food. Combining these two assumptions, the model predicts that selective grazing on small but nutritious food will favor evolution of large phytoplankton of low nutritional quality. Hence, a size-dependent change in food quality may explain why phytoplankton of large size often dominate in waters with high grazing pressure. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>hytoplankton are among the smallest primary producers on Earth, and yet display a wide range of cell sizes. Typically, small phytoplankton species are stronger nutrient competitors than large phytoplankton species, but they are also more easily grazed. In contrast, evolution of large phytoplankton is often explained as a physical defense against grazing. Conceptually this explanation is problematic, however, because zooplankton can coevolve larger size to counter this size-dependent escape from grazing. Here, we hypothesize that there is another advantage for the evolution of large phytoplankton size not so readily overcome: larger phytoplankton often provide lower nutritional quality for zooplankton. We investigate this hypothesis by analyzing an eco-evolutionary model that combines the ecological stoichiometry of phytoplankton-zooplankton interactions with coevolution of phytoplankton and zooplankton size. In our model, evolution of cell size modifies the nutrient uptake kinetics of phytoplankton according to known allometric relationships, which in turn affect the nutritional quality of phytoplankton. With this size-based mechanism, the model predicts that low grazing pressure or nonselective grazing by zooplankton favors evolution of small phytoplankton cells of high nutritional quality. In contrast, selective grazing for nutritious food favors evolution of large phytoplankton of low nutritional quality, which are preyed upon by medium- to large-sized zooplankton. This size-dependent change in food quality may explain the commonly observed shift from dominance by small picophytoplankton in oligotrophic waters with low grazing pressure to large phytoplankton species in nutrient-rich waters with high grazing pressure. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 18 Sep 2019 05:00:00 GMT “The effects of body mass on immune cell concentrations of terrestrial mammals” https://amnat.org/an/newpapers/Jan-Downs.html Cynthia J. Downs, Ned A. Dochtermann, Ray Ball, Kirk C. Klasing, and Lynn B. Martin (Jan 2020) Read the Article (Just Accepted) Neutrophils increase disproportionately with body mass. An elephant’s immune system isn’t a mouse’s writ large What species is better at fighting an infection, a mouse or an elephant? Body size is one of the most noticeable differences among species, but relationships between immune defenses and body size have largely been unstudied. Drs. Cynthia Downs (Hamilton College, currently at State University of New York, College of Environmental Science and Forestry), Ned Dochtermann (North Dakota State University), Kirk Klasing (University of California, Davis), Ray Ball (Eckerd College), and Lynn (Marty) Martin (University of South Florida) investigated whether body mass was related to concentrations of two important immune cell types in the blood among 100s of species of mammals ranging from tiny Jamaican fruit bats (~40&nbsp;g) to giant killer whales (~5,600&nbsp;kg). The researchers found that concentrations of lymphocytes, one type of white blood cell, didn’t change in any special way with body size. That is, a mouse and an elephant have the same number of lymphocytes per ml of blood. In contrast, big mammals had far, far more neutrophils in circulation than small species. Neutrophils are involved in early immune responses to many different kinds of invaders including bacteria and even bigger parasites such as worms. The researchers speculate that larger mammals might need so many more circulating neutrophils to overcome the inherent advantage that infectious agents have over the animals they infect. This advantage arises because small things replicate their cells much faster than big things; to offset this benefit of being small, big things keep around a large pool of nasty cells to attack invaders. Altogether, this work shows that for some types of immune defenses, large and small mammals are fundamentally different. This insight could help us develop better ways to link results from lab mice to improvements of human health as well as enable us to make predictions about the immune systems of species never before studied. These data could also even help wildlife managers predict how good a species could be as a host for a newly emerging disease. This work was funded by National Science Foundation grant numbers 0947177, 1257773, 656618, 165655. Abstract Theory predicts that body mass should affect the way organisms evolve and use immune defenses. We investigated the relationship between body mass and blood neutrophil and lymphocyte concentrations among 250+ terrestrial mammalian species. We tested whether existing theories (e.g., Protecton Theory, immune system complexity, and rate of metabolism) accurately predicted the scaling of immune cell concentrations. We also evaluated the predictive power of body mass for these leukocyte concentrations compared to sociality, diet, life history, and phylogenetic relatedness. Phylogeny explained >70% of variation in both lymphocytes and neutrophils, and body mass appeared more informative than other interspecific trait variation. In the best-fit mass-only model, neutrophils scaled hypermetrically (b&nbsp;=&nbsp;0.11) with body mass whereas lymphocytes scaled isometrically. Extrapolating to total cell numbers, this exponent means that an African elephant circulates 13.3 million times the neutrophils of a house mouse, whereas their masses differ by only 250k-fold. We hypothesize that such high neutrophil numbers might offset the i) higher overall parasite exposure that large animals face and/or ii) the higher relative replication capacities of pathogens to host cells. More forthcoming papers &raquo; <p>Cynthia J. Downs, Ned A. Dochtermann, Ray Ball, Kirk C. Klasing, and Lynn B. Martin (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706235">Read the Article</a></i> (Just Accepted) </p> <p><b>Neutrophils increase disproportionately with body mass. An elephant’s immune system isn’t a mouse’s writ large </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hat species is better at fighting an infection, a mouse or an elephant? Body size is one of the most noticeable differences among species, but relationships between immune defenses and body size have largely been unstudied. Drs. Cynthia Downs (Hamilton College, currently at State University of New York, College of Environmental Science and Forestry), Ned Dochtermann (North Dakota State University), Kirk Klasing (University of California, Davis), Ray Ball (Eckerd College), and Lynn (Marty) Martin (University of South Florida) investigated whether body mass was related to concentrations of two important immune cell types in the blood among 100s of species of mammals ranging from tiny Jamaican fruit bats (~40&nbsp;g) to giant killer whales (~5,600&nbsp;kg). The researchers found that concentrations of lymphocytes, one type of white blood cell, didn’t change in any special way with body size. That is, a mouse and an elephant have the same number of lymphocytes per ml of blood. In contrast, big mammals had far, far more neutrophils in circulation than small species. Neutrophils are involved in early immune responses to many different kinds of invaders including bacteria and even bigger parasites such as worms. The researchers speculate that larger mammals might need so many more circulating neutrophils to overcome the inherent advantage that infectious agents have over the animals they infect. This advantage arises because small things replicate their cells much faster than big things; to offset this benefit of being small, big things keep around a large pool of nasty cells to attack invaders. </p><p>Altogether, this work shows that for some types of immune defenses, large and small mammals are fundamentally different. This insight could help us develop better ways to link results from lab mice to improvements of human health as well as enable us to make predictions about the immune systems of species never before studied. These data could also even help wildlife managers predict how good a species could be as a host for a newly emerging disease. This work was funded by National Science Foundation grant numbers 0947177, 1257773, 656618, 165655. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>heory predicts that body mass should affect the way organisms evolve and use immune defenses. We investigated the relationship between body mass and blood neutrophil and lymphocyte concentrations among 250+ terrestrial mammalian species. We tested whether existing theories (e.g., Protecton Theory, immune system complexity, and rate of metabolism) accurately predicted the scaling of immune cell concentrations. We also evaluated the predictive power of body mass for these leukocyte concentrations compared to sociality, diet, life history, and phylogenetic relatedness. Phylogeny explained >70% of variation in both lymphocytes and neutrophils, and body mass appeared more informative than other interspecific trait variation. In the best-fit mass-only model, neutrophils scaled hypermetrically (<i>b</i>&nbsp;=&nbsp;0.11) with body mass whereas lymphocytes scaled isometrically. Extrapolating to total cell numbers, this exponent means that an African elephant circulates 13.3 million times the neutrophils of a house mouse, whereas their masses differ by only 250k-fold. We hypothesize that such high neutrophil numbers might offset the i) higher overall parasite exposure that large animals face and/or ii) the higher relative replication capacities of pathogens to host cells. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 18 Sep 2019 05:00:00 GMT “Spatial population structure determines extinction risk in climate-induced range shifts” https://amnat.org/an/newpapers/Jan-Weiss-Lehman.html Christopher Weiss-Lehman and Allison Shaw (Jan 2020) Read the Article (Just Accepted) Spatial population structure inhibits range shifts via impacts on eco-evolutionary dynamics of dispersal and adaptation Species moving to track climate change have revealed an interesting phenomenon that scientists hope could help them as climate change continues. As species move to track the environmental conditions to which they are adapted, many have undergone rapid, evolved increases in traits related to movement (e.g. limb length or seed size and shape). These changes could substantially improve species’ abilities to track changing environmental conditions, but new research from Drs. Christopher Weiss-Lehman and Allison Shaw at the University of Minnesota suggest it could also lead to further problems down the road. Dr. Weiss-Lehman, now at the University of Wyoming, created a model in collaboration with Dr. Shaw to test the relationship between evolution of dispersal (i.e. traits related to movement and settlement) and extinction risk due to climate change. All populations in the model rapidly evolve increased dispersal, allowing them to keep pace with changing environmental conditions. However, Drs. Weiss-Lehman and Shaw noticed an odd pattern. Under some scenarios, populations still face extremely high extinction risks despite rapid evolution of dispersal. In populations structured by adaptation to variable local conditions, increased dispersal leads to the increased exchange of genetic material among subpopulations. This results in greater genetic similarity throughout the population and a corresponding reduction in adaptation to variable local conditions. This loss of adaptation to local conditions reduces population performance and substantially increases population extinction risk in such scenarios. Thus, while rapid evolution of dispersal can allow species to better track climate change, it can also increase population extinction risk by reducing the degree of adaptation to local conditions. While predictions from models such as this can provide important insights for conservation in the face of climate change, more research is urgently needed to better understand how these model predictions will play out for real species. Abstract Climate change is an escalating threat facing populations around the globe, necessitating a robust understanding of the ecological and evolutionary mechanisms dictating population responses. However, populations do not respond to climate change in isolation, but rather in the context of their existing ranges. In particular, spatial population structure within a range (e.g. trait clines, starkness of range edges, etc.) likely interacts with other ecological and evolutionary processes during climate-induced range shifts. Here, we use an individual-based model to explore the interacting roles of several such factors in range shift dynamics. We show that increased spatial population structure (driven primarily by a steeper environmental gradient) severely increases a population's extinction risk. Further, we show that while evolution of heightened dispersal during range shifts can aid populations in tracking changing conditions, it can also interact negatively with adaptation to the environmental gradient, leading to reduced fitness and contributing to the increased extinction risk observed in populations structured along steep environmental gradients. Our results demonstrate that the effect of dispersal evolution on range shifting populations is dependent on environmental context and that spatial population structure can substantially increase extinction risk in range shifts. More forthcoming papers &raquo; <p>Christopher Weiss-Lehman and Allison Shaw (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706259">Read the Article</a></i> (Just Accepted) </p> <p><b>Spatial population structure inhibits range shifts via impacts on eco-evolutionary dynamics of dispersal and adaptation </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>pecies moving to track climate change have revealed an interesting phenomenon that scientists hope could help them as climate change continues. As species move to track the environmental conditions to which they are adapted, many have undergone rapid, evolved increases in traits related to movement (e.g. limb length or seed size and shape). These changes could substantially improve species’ abilities to track changing environmental conditions, but new research from Drs. Christopher Weiss-Lehman and Allison Shaw at the University of Minnesota suggest it could also lead to further problems down the road. </p><p>Dr. Weiss-Lehman, now at the University of Wyoming, created a model in collaboration with Dr. Shaw to test the relationship between evolution of dispersal (i.e. traits related to movement and settlement) and extinction risk due to climate change. All populations in the model rapidly evolve increased dispersal, allowing them to keep pace with changing environmental conditions. However, Drs. Weiss-Lehman and Shaw noticed an odd pattern. Under some scenarios, populations still face extremely high extinction risks despite rapid evolution of dispersal. In populations structured by adaptation to variable local conditions, increased dispersal leads to the increased exchange of genetic material among subpopulations. This results in greater genetic similarity throughout the population and a corresponding reduction in adaptation to variable local conditions. This loss of adaptation to local conditions reduces population performance and substantially increases population extinction risk in such scenarios. </p><p>Thus, while rapid evolution of dispersal can allow species to better track climate change, it can also increase population extinction risk by reducing the degree of adaptation to local conditions. While predictions from models such as this can provide important insights for conservation in the face of climate change, more research is urgently needed to better understand how these model predictions will play out for real species. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>limate change is an escalating threat facing populations around the globe, necessitating a robust understanding of the ecological and evolutionary mechanisms dictating population responses. However, populations do not respond to climate change in isolation, but rather in the context of their existing ranges. In particular, spatial population structure within a range (e.g. trait clines, starkness of range edges, etc.) likely interacts with other ecological and evolutionary processes during climate-induced range shifts. Here, we use an individual-based model to explore the interacting roles of several such factors in range shift dynamics. We show that increased spatial population structure (driven primarily by a steeper environmental gradient) severely increases a population's extinction risk. Further, we show that while evolution of heightened dispersal during range shifts can aid populations in tracking changing conditions, it can also interact negatively with adaptation to the environmental gradient, leading to reduced fitness and contributing to the increased extinction risk observed in populations structured along steep environmental gradients. Our results demonstrate that the effect of dispersal evolution on range shifting populations is dependent on environmental context and that spatial population structure can substantially increase extinction risk in range shifts. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 18 Sep 2019 05:00:00 GMT “The evolutionary origin of associative learning” https://amnat.org/an/newpapers/Jan-Pontes.html Anselmo C. Pontes, Robert B. Mobley, Charles Ofria, Christoph Adami, and Fred C. Dyer (Jan 2020) Read the Article (Just Accepted) Digital evolution uncovers the origin of associative learning and reflexive behaviors animal cognition artificial life Though learning is crucial to most behaviors, we know very little about how it evolved. Understanding how learning first appeared could provide clues as to how it works, and have implications for many fields such as neuroscience, education, psychology, and animal behavior. It may also help us build computers that learn the same way natural organisms do. The results from this study are the first demonstration of the evolution of associative learning in an artificial organism without a brain. Since the evolution of learning cannot be observed through fossils – and would take more than a lifetime to watch in nature – the MSU interdisciplinary team composed of biologists and computer scientists used a digital evolution program that allowed them to observe tens of thousands of generations of evolution in just a few hours, a feat unachievable with living systems. In the study, organisms evolved to learn and use environmental signals to help them navigate the environment and find food. While the environment was simulated, the evolution was real. The programs that controlled the digital organism were subject to genetic variation from mutation, inheritance, and competitive selection. Organisms were tasked to follow a trail alongside signals that – if interpreted correctly – pointed where the path went next. In the beginning of the simulation, organisms were “blank slates,” incapable of sensing, moving, or learning. Over the generations, organisms evolved more and more complex behaviors, even learning by association and correcting mistakes. Interestingly, MSU researchers were not just able to see how certain environments fostered the evolution of learning, but how populations evolved through the same behavioral phases that previous scientists speculated should happen but didn’t have the technology to see. Abstract Learning is a widespread ability among animals and, like physical traits, is subject to evolution. But how did learning first arise? What selection pressures and phenotypic preconditions fostered its evolution? Neither the fossil record nor phylogenetic comparative studies provide answers to these questions. Here, we take a novel approach by studying digital organisms in environments that promote the evolution of navigation and associative learning. Starting with a non-learning, sessile ancestor, we evolve multiple populations in four different environments, each consisting of nutrient trails with various layouts. Trail nutrients cue organisms on which direction to follow, provided they evolve to acquire and use those cues. Thus, each organism is tested on how well it navigates a randomly selected trail before reproducing. We find that behavior evolves modularly and in a predictable sequence, where simpler behaviors are necessary precursors for more complex ones. Associative learning is only one of many successful behaviors to evolve, and its origin depends on the environment possessing certain information patterns that organisms can exploit. Environmental patterns that are stable across generations foster the evolution of reflexive behavior, while environmental patterns that vary across generations, but remain consistent for periods within an organism’s lifetime, foster the evolution of learning behavior. Both types of environmental patterns are necessary, since the prior evolution of simple reflexive behaviors provides the building blocks for learning to arise. Finally, we observe that an intrinsic value system evolves alongside behavior and supports associative learning by providing reinforcement for behavior conditioning. More forthcoming papers &raquo; &nbsp; <p>Anselmo C. Pontes, Robert B. Mobley, Charles Ofria, Christoph Adami, and Fred C. Dyer (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706252">Read the Article</a></i> (Just Accepted) </p> <p><b>Digital evolution uncovers the origin of associative learning and reflexive behaviors animal cognition artificial life </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>hough learning is crucial to most behaviors, we know very little about how it evolved. Understanding how learning first appeared could provide clues as to how it works, and have implications for many fields such as neuroscience, education, psychology, and animal behavior. It may also help us build computers that learn the same way natural organisms do. </p><p>The results from this study are the first demonstration of the evolution of associative learning in an artificial organism without a brain. Since the evolution of learning cannot be observed through fossils – and would take more than a lifetime to watch in nature – the MSU interdisciplinary team composed of biologists and computer scientists used a digital evolution program that allowed them to observe tens of thousands of generations of evolution in just a few hours, a feat unachievable with living systems. </p><p>In the study, organisms evolved to learn and use environmental signals to help them navigate the environment and find food. While the environment was simulated, the evolution was real. The programs that controlled the digital organism were subject to genetic variation from mutation, inheritance, and competitive selection. Organisms were tasked to follow a trail alongside signals that – if interpreted correctly – pointed where the path went next. In the beginning of the simulation, organisms were “blank slates,” incapable of sensing, moving, or learning. Over the generations, organisms evolved more and more complex behaviors, even learning by association and correcting mistakes. </p><p>Interestingly, MSU researchers were not just able to see how certain environments fostered the evolution of learning, but how populations evolved through the same behavioral phases that previous scientists speculated should happen but didn’t have the technology to see.</p><hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">L</span>earning is a widespread ability among animals and, like physical traits, is subject to evolution. But how did learning first arise? What selection pressures and phenotypic preconditions fostered its evolution? Neither the fossil record nor phylogenetic comparative studies provide answers to these questions. Here, we take a novel approach by studying digital organisms in environments that promote the evolution of navigation and associative learning. Starting with a non-learning, sessile ancestor, we evolve multiple populations in four different environments, each consisting of nutrient trails with various layouts. Trail nutrients cue organisms on which direction to follow, provided they evolve to acquire and use those cues. Thus, each organism is tested on how well it navigates a randomly selected trail before reproducing. We find that behavior evolves modularly and in a predictable sequence, where simpler behaviors are necessary precursors for more complex ones. Associative learning is only one of many successful behaviors to evolve, and its origin depends on the environment possessing certain information patterns that organisms can exploit. Environmental patterns that are stable across generations foster the evolution of reflexive behavior, while environmental patterns that vary across generations, but remain consistent for periods within an organism&rsquo;s lifetime, foster the evolution of learning behavior. Both types of environmental patterns are necessary, since the prior evolution of simple reflexive behaviors provides the building blocks for learning to arise. Finally, we observe that an intrinsic value system evolves alongside behavior and supports associative learning by providing reinforcement for behavior conditioning.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> <p>&nbsp;</p> Wed, 18 Sep 2019 05:00:00 GMT “Comparing life histories across taxonomic groups in multiple dimensions: how mammal-like are insects?” https://amnat.org/an/newpapers/Jan-Bakewell-A.html Adam T. Bakewell, Katie E. Davis, Robert P. Freckleton, Nick J. B. Isaac, and Peter J. Mayhew (Jan 2020) Read the Article (Just Accepted) Fast-slow continuum is less pronounced in Orthoptera than in birds/mammals, instead trait covariation is reptile-like Abstract Explaining variation in life histories remains a major challenge because they are multi-dimensional and there are many competing explanatory theories and paradigms. An influential concept in life history theory is the ‘fast-slow continuum’, exemplified by mammals. Determining the utility of such concepts across taxonomic groups requires comparison of the groups’ life histories in multidimensional space. Insects display enormous species richness and phenotypic diversity, but testing hypotheses like the ‘fast-slow continuum’ has been inhibited by incomplete trait data. We use phylogenetic imputation to generate complete datasets of seven life history traits in orthopterans (grasshoppers and crickets) and examine the robustness of these imputations for our findings. Three phylogenetic principal components explain 83-96% of variation in these data. We find consistent evidence of an axis mostly following expectations of a ‘fast-slow continuum’, except that ‘slow’ species produce larger, not smaller, clutches of eggs. We show that the principal axes of variation in orthopterans and reptiles are mutually explanatory, as are those of mammals and birds. Essentially, trait covariation in Orthoptera, with ‘slow’ species producing larger clutches, is more reptile-like than mammal-or-bird-like. We conclude that the ‘fast-slow continuum’ is less pronounced in Orthoptera than in birds and mammals, reducing the universal relevance of this pattern, and the theories that predict it. More forthcoming papers &raquo; <p>Adam T. Bakewell, Katie E. Davis, Robert P. Freckleton, Nick J. B. Isaac, and Peter J. Mayhew (Jan 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/706195">Read the Article</a></i> (Just Accepted)</p> <p><b>Fast-slow continuum is less pronounced in Orthoptera than in birds/mammals, instead trait covariation is reptile-like </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>xplaining variation in life histories remains a major challenge because they are multi-dimensional and there are many competing explanatory theories and paradigms. An influential concept in life history theory is the ‘fast-slow continuum’, exemplified by mammals. Determining the utility of such concepts across taxonomic groups requires comparison of the groups’ life histories in multidimensional space. Insects display enormous species richness and phenotypic diversity, but testing hypotheses like the ‘fast-slow continuum’ has been inhibited by incomplete trait data. We use phylogenetic imputation to generate complete datasets of seven life history traits in orthopterans (grasshoppers and crickets) and examine the robustness of these imputations for our findings. Three phylogenetic principal components explain 83-96% of variation in these data. We find consistent evidence of an axis mostly following expectations of a ‘fast-slow continuum’, except that ‘slow’ species produce larger, not smaller, clutches of eggs. We show that the principal axes of variation in orthopterans and reptiles are mutually explanatory, as are those of mammals and birds. Essentially, trait covariation in Orthoptera, with ‘slow’ species producing larger clutches, is more reptile-like than mammal-or-bird-like. We conclude that the ‘fast-slow continuum’ is less pronounced in Orthoptera than in birds and mammals, reducing the universal relevance of this pattern, and the theories that predict it. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 17 Sep 2019 05:00:00 GMT “Testosterone modulates status-specific patterns of cooperation in a social network” https://amnat.org/an/newpapers/Jan-Ryder.html T. Brandt Ryder, Roslyn Dakin, Ben J. Vernasco, Brian S. Evans, Brent M. Horton, and Ignacio T. Moore (Jan 2020) Read the Article (Just Accepted) Testosterone helps male birds ascend in social status, but too much is detrimental to their cooperative behavior Cooperation has fascinated biologists for hundreds of years. Why are some individuals more cooperative and others more competitive? What underlies these differences in behavior and how do those individual differences contribute to stable cooperative societies? Although biologists have long known that hormones shape behavior, our understanding of the mechanisms that enable behavioral flexibility in cooperative social networks remains virtually unstudied. Ryder et al. studied the hormonal basis of variation in cooperative behavior in a lekking tropical birds. Leks are a social system where males join together and display to attract females. Using a novel biologging system, the researchers autonomously collected data on the cooperative social networks (i.e., who interacts with whom and the frequency of those interactions). These data were combined with repeated measures of circulating testosterone to ask if circulating hormones drive individual differences in cooperative tendencies. The researchers found that testosterone, a hormone long known for its mediation of aggression, can also influence social behavior in a cooperative social system. High testosterone was associated with increased cooperative tendencies in young, non-territorial males, but it was antagonistic to those same behaviors once a male acquired his own territorial at the lek. This research highlights how hormones can have diverse effects on behavior, depending upon an animal’s life stage, and it underscores the importance of testosterone in context-dependent behavioral flexibility. Abstract Stable cooperation requires plasticity whereby individuals are able to express competitive or cooperative behaviors depending on social context. To date, however, the physiological mechanisms that underlie behavioral variation in cooperative systems are poorly understood. We studied hormone-mediated behavior in the wire-tailed manakin (Pipra filicauda), a gregarious songbird whose cooperative partnerships and competition for status are both crucial for fitness. We used automated telemetry to monitor >&nbsp;36,000 cooperative interactions among male manakins over three field seasons, and we examined how circulating testosterone affects cooperation using >&nbsp;500 hormone samples. Observational data show that in non-territorial floater males, high testosterone is associated with increased cooperative behaviors and subsequent ascension to territorial status. In territory-holding males, however, both observational and experimental evidence demonstrate that high testosterone antagonizes cooperation. Moreover, circulating testosterone explains significant variation (2–8%) in social behavior within each status class. Collectively, our findings show that the hormonal control of cooperation depends on a male’s social status. We propose that the status-dependent reorganization of hormone-regulatory pathways can facilitate stable cooperative partnerships, and thus provide direct fitness benefits for males. More forthcoming papers &raquo; <p>T. Brandt Ryder, Roslyn Dakin, Ben J. Vernasco, Brian S. Evans, Brent M. Horton, and Ignacio T. Moore (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706236">Read the Article</a></i> (Just Accepted) </p> <p><b>Testosterone helps male birds ascend in social status, but too much is detrimental to their cooperative behavior </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>ooperation has fascinated biologists for hundreds of years. Why are some individuals more cooperative and others more competitive? What underlies these differences in behavior and how do those individual differences contribute to stable cooperative societies? Although biologists have long known that hormones shape behavior, our understanding of the mechanisms that enable behavioral flexibility in cooperative social networks remains virtually unstudied. </p><p>Ryder et al. studied the hormonal basis of variation in cooperative behavior in a lekking tropical birds. Leks are a social system where males join together and display to attract females. Using a novel biologging system, the researchers autonomously collected data on the cooperative social networks (i.e., who interacts with whom and the frequency of those interactions). These data were combined with repeated measures of circulating testosterone to ask if circulating hormones drive individual differences in cooperative tendencies. </p><p>The researchers found that testosterone, a hormone long known for its mediation of aggression, can also influence social behavior in a cooperative social system. High testosterone was associated with increased cooperative tendencies in young, non-territorial males, but it was antagonistic to those same behaviors once a male acquired his own territorial at the lek. This research highlights how hormones can have diverse effects on behavior, depending upon an animal’s life stage, and it underscores the importance of testosterone in context-dependent behavioral flexibility.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>table cooperation requires plasticity whereby individuals are able to express competitive or cooperative behaviors depending on social context. To date, however, the physiological mechanisms that underlie behavioral variation in cooperative systems are poorly understood. We studied hormone-mediated behavior in the wire-tailed manakin (<i>Pipra filicauda</i>), a gregarious songbird whose cooperative partnerships and competition for status are both crucial for fitness. We used automated telemetry to monitor &gt;&nbsp;36,000 cooperative interactions among male manakins over three field seasons, and we examined how circulating testosterone affects cooperation using &gt;&nbsp;500 hormone samples. Observational data show that in non-territorial floater males, high testosterone is associated with increased cooperative behaviors and subsequent ascension to territorial status. In territory-holding males, however, both observational and experimental evidence demonstrate that high testosterone antagonizes cooperation. Moreover, circulating testosterone explains significant variation (2&ndash;8%) in social behavior within each status class. Collectively, our findings show that the hormonal control of cooperation depends on a male’s social status. We propose that the status-dependent reorganization of hormone-regulatory pathways can facilitate stable cooperative partnerships, and thus provide direct fitness benefits for males. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 17 Sep 2019 05:00:00 GMT “Fecundity-longevity trade-off, vertical transmission, and evolution of virulence in sterilizing pathogens” https://amnat.org/an/newpapers/Jan-Janouskova-A.html Eva Janoušková and Luděk Berec (Jan 2020) Read the Article (Just Accepted) We for the first time show that the fecundity-longevity trade-off is a relevant player in sterility virulence evolution Abstract Sterilizing pathogens are common, yet studies focused on how such pathogens respond adaptively to fecundity reductions caused to their hosts are rare. Here we assume that the infected hosts, due to redistributing energy resources saved by reduced fecundity, have increased longevity and focus on exploring the consequences of such a fecundity-longevity trade-off on sterility virulence evolution in the pathogens. We find that the trade-off itself cannot prevent evolution of full sterilization. Therefore, we allow for vertical transmission and reveal that the fecundity-longevity trade-off strongly determines the threshold efficiency of vertical transmission above which partial host sterilization evolves. Partial sterilization may appear as an intermediate level of sterility virulence or as a stable dimorphism at which avirulent and highly virulent strains coexist. The fecundity-longevity trade-off significantly contributes to determining the actual outcome, in many cases countering predictions made in the absence of this trade-off. It is known that in well-mixed populations, partial sterilization may evolve in pathogens under a combination of horizontal and vertical transmission. Our study highlights that this is independent of the form of horizontal transmission and the type of density dependence in host demography, and that the fecundity-longevity trade-off is an important player in sterility virulence evolution. More forthcoming papers &raquo; <p>Eva Janoušková and Luděk Berec (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706182">Read the Article</a></i> (Just Accepted) </p> <p><b>We for the first time show that the fecundity-longevity trade-off is a relevant player in sterility virulence evolution </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>terilizing pathogens are common, yet studies focused on how such pathogens respond adaptively to fecundity reductions caused to their hosts are rare. Here we assume that the infected hosts, due to redistributing energy resources saved by reduced fecundity, have increased longevity and focus on exploring the consequences of such a fecundity-longevity trade-off on sterility virulence evolution in the pathogens. We find that the trade-off itself cannot prevent evolution of full sterilization. Therefore, we allow for vertical transmission and reveal that the fecundity-longevity trade-off strongly determines the threshold efficiency of vertical transmission above which partial host sterilization evolves. Partial sterilization may appear as an intermediate level of sterility virulence or as a stable dimorphism at which avirulent and highly virulent strains coexist. The fecundity-longevity trade-off significantly contributes to determining the actual outcome, in many cases countering predictions made in the absence of this trade-off. It is known that in well-mixed populations, partial sterilization may evolve in pathogens under a combination of horizontal and vertical transmission. Our study highlights that this is independent of the form of horizontal transmission and the type of density dependence in host demography, and that the fecundity-longevity trade-off is an important player in sterility virulence evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 17 Sep 2019 05:00:00 GMT “Niche construction affects the variability and strength of natural selection” https://amnat.org/an/newpapers/Jan-Clark.html Andrew D. Clark, Dominik Deffner, Kevin Laland, John Odling-Smee, and John Endler (Jan 2020) Read the Article (Just Accepted) A meta-analysis of selection gradients shows that niche construction affects the variability and strength of selection That organisms modify their local environments (i.e. nest-building in birds, dam-building in beavers) has long been known and studied by evolutionary biologists. However, it is less certain how animal-built artefacts and choices (a.k.a. ‘niche construction’) influence the natural selection that they experience. In this study, Andrew Clark, Dominik Deffner, Kevin Laland, John Odling-Smee, and John Endler conduct statistical analyses of data from published studies measuring natural selection in the wild to test whether such organismconstructed environmental elements differ from non-constructed environmental components in the strength and variability of natural selection generated. Such a difference is expected because organisms partly control and regulate their environments by building and modifying conditions in nests, burrows, and mounds, and also choosing habitats, resources, and foraging locations. These activities typically act to ensure that the environmental variables they experience remain within suitable tolerance ranges. As predicted, the analysis reveals an overall lower magnitude of selection, and reduced temporal and spatial variation in selection, associated with constructed elements of the environment. The study confirms that organism-manufactured or chosen components of environments may have qualitatively different properties from other environmental features, and highlights how the activities of organisms may shape selection in a manner not yet fully appreciated. Abstract Consideration of the properties of the sources of selection potentially helps biologists to account for variation in selection. Here we explore how the variability of natural selection is affected by organisms that regulate the experienced environment through their activities (whether by constructing components of their local environments such as nests, burrows, or pupal cases, or by choosing suitable resources). Specifically, we test the predictions that organism-constructed sources of selection that buffer environmental variation will result in (i) reduced variation in selection gradients, including reduced variation between (a) years (temporal variation), and (b) locations (spatial variation), and (ii) weaker directional selection, relative to non-constructed sources. Using compiled datasets of 1045 temporally replicated, 257 spatially replicated, and a pooled dataset of 1230 selection gradients, we find compelling evidence for reduced temporal variation and weaker selection, in response to constructed compared to non-constructed sources of selection, and some evidence for reduced spatial variation in selection. These findings, which remained robust to alternative datasets, taxa, analytical methods, definitions of constructed/non-constructed, and other tests of reliability, suggest that organism-manufactured or chosen components of environments may have qualitatively different properties from other environmental features. More forthcoming papers &raquo; <p>Andrew D. Clark, Dominik Deffner, Kevin Laland, John Odling-Smee, and John Endler (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706196">Read the Article</a></i> (Just Accepted) </p> <p><b>A meta-analysis of selection gradients shows that niche construction affects the variability and strength of selection </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>hat organisms modify their local environments (i.e. nest-building in birds, dam-building in beavers) has long been known and studied by evolutionary biologists. However, it is less certain how animal-built artefacts and choices (a.k.a. ‘niche construction’) influence the natural selection that they experience. In this study, Andrew Clark, Dominik Deffner, Kevin Laland, John Odling-Smee, and John Endler conduct statistical analyses of data from published studies measuring natural selection in the wild to test whether such organismconstructed environmental elements differ from non-constructed environmental components in the strength and variability of natural selection generated. Such a difference is expected because organisms partly control and regulate their environments by building and modifying conditions in nests, burrows, and mounds, and also choosing habitats, resources, and foraging locations. These activities typically act to ensure that the environmental variables they experience remain within suitable tolerance ranges. As predicted, the analysis reveals an overall lower magnitude of selection, and reduced temporal and spatial variation in selection, associated with constructed elements of the environment. The study confirms that organism-manufactured or chosen components of environments may have qualitatively different properties from other environmental features, and highlights how the activities of organisms may shape selection in a manner not yet fully appreciated.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsideration of the properties of the sources of selection potentially helps biologists to account for variation in selection. Here we explore how the variability of natural selection is affected by organisms that regulate the experienced environment through their activities (whether by constructing components of their local environments such as nests, burrows, or pupal cases, or by choosing suitable resources). Specifically, we test the predictions that organism-constructed sources of selection that buffer environmental variation will result in (i) reduced variation in selection gradients, including reduced variation between (a) years (temporal variation), and (b) locations (spatial variation), and (ii) weaker directional selection, relative to non-constructed sources. Using compiled datasets of 1045 temporally replicated, 257 spatially replicated, and a pooled dataset of 1230 selection gradients, we find compelling evidence for reduced temporal variation and weaker selection, in response to constructed compared to non-constructed sources of selection, and some evidence for reduced spatial variation in selection. These findings, which remained robust to alternative datasets, taxa, analytical methods, definitions of constructed/non-constructed, and other tests of reliability, suggest that organism-manufactured or chosen components of environments may have qualitatively different properties from other environmental features. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 17 Sep 2019 05:00:00 GMT “Deer indirectly alter the reproductive strategy and operational sex ratio of an unpalatable forest perennial” https://amnat.org/an/newpapers/Jan-Bialic-Murphy.html Lalasia Bialic-Murphy, Christopher D. Heckel, Robert M. McElderry, and Susan Kalisz (Jan 2020) Read the Article (Just Accepted) Deer indirectly affect the reproductive strategy of an unpalatable forest perennial While necessary for life to persist, reproduction is a costly endeavor. Many plants and animals can reproduce both sexually and asexually and can express both male and female form. To examine how human-induced changes in the environment alter a species reproductive strategy, Bialic-Murphy et al. studied a sexually labile understory perennial, Arisaema triphyllum (Jack in the pulpit), across a deer impact gradient. Arisaema is strongly influenced by environmental conditions, and individuals commonly switch between male and female form multiple times over their lifespan (40+ years). Humans have dramatically reduced the abundance of large carnivores in native ecosystems, which in turn has increased the density of large herbivores (e.g., white-tailed deer). Increased deer impact is known to have significant effects on soil dynamics, including a decrease in soil moisture and an increase in soil compaction. In this study, researchers show that increased deer impacts on environmental conditions result in delayed female sex expression for Arisaema to unsustainably large plant sizes and leads to more pronounced plant shrinkage following seed production, effectively increasing the cost of reproduction. Arisaema at high deer impact also reproduces less often and invest more in asexual reproduction than sexual reproduction. Populations at high deer impact sites are extremely male-biased, with only 7% of the sexually reproductive plants producing female flowers. These results illustrate the dramatic effects of human-induced change on the sex expression of plants in the forest understory. Abstract Environmental conditions impose restrictions and costs on reproduction. Multiple reproductive options exist when increased reproductive costs drive plant populations toward alternative reproductive strategies. Using four years of demographic data across a deer impact gradient, where deer alter the abiotic environment, we parameterize a size-dependent integral projection model for a sexually labile and unpalatable forest perennial to investigate the demographic processes driving differentiation in the operational sex ratio (OSR) of local populations. In addition to a relative increase in asexual reproduction, our results illustrate that non-trophic indirect effects by overabundant deer on this perennial result in delayed female sex expression to unsustainably large plant sizes and leads to more pronounced plant shrinkage following female sex expression, effectively increasing the cost of reproduction. Among plants of reproductive age, increased deer impact decreases the size-dependent probability of flowering and reduces reproductive consistency over time. This pattern in sex expression skews populations toward female-biased OSRs at low deer impact sites and male-biased OSRs at intermediate and high deer impact sites. While this shift toward a male-biased OSR may ameliorate pollen limitation, it also decreases the effective population size when coupled with increased asexual reproduction. The divergence of reproductive strategies and reduced lifetime fitness in response to indirect deer impacts illustrate the persistent long-term effects of overabundant herbivores on unpalatable understory perennials. More forthcoming papers &raquo; <p>Lalasia Bialic-Murphy, Christopher D. Heckel, Robert M. McElderry, and Susan Kalisz (Jan 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706253">Read the Article</a></i> (Just Accepted) </p> <p><b>Deer indirectly affect the reproductive strategy of an unpalatable forest perennial </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">W</span>hile necessary for life to persist, reproduction is a costly endeavor. Many plants and animals can reproduce both sexually and asexually and can express both male and female form. To examine how human-induced changes in the environment alter a species reproductive strategy, Bialic-Murphy et al. studied a sexually labile understory perennial, <i>Arisaema triphyllum</i> (Jack in the pulpit), across a deer impact gradient. <i>Arisaema</i> is strongly influenced by environmental conditions, and individuals commonly switch between male and female form multiple times over their lifespan (40+ years). Humans have dramatically reduced the abundance of large carnivores in native ecosystems, which in turn has increased the density of large herbivores (e.g., white-tailed deer). Increased deer impact is known to have significant effects on soil dynamics, including a decrease in soil moisture and an increase in soil compaction. In this study, researchers show that increased deer impacts on environmental conditions result in delayed female sex expression for <i>Arisaema</i> to unsustainably large plant sizes and leads to more pronounced plant shrinkage following seed production, effectively increasing the cost of reproduction. <i>Arisaema</i> at high deer impact also reproduces less often and invest more in asexual reproduction than sexual reproduction. Populations at high deer impact sites are extremely male-biased, with only 7% of the sexually reproductive plants producing female flowers. These results illustrate the dramatic effects of human-induced change on the sex expression of plants in the forest understory.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">E</span>nvironmental conditions impose restrictions and costs on reproduction. Multiple reproductive options exist when increased reproductive costs drive plant populations toward alternative reproductive strategies. Using four years of demographic data across a deer impact gradient, where deer alter the abiotic environment, we parameterize a size-dependent integral projection model for a sexually labile and unpalatable forest perennial to investigate the demographic processes driving differentiation in the operational sex ratio (OSR) of local populations. In addition to a relative increase in asexual reproduction, our results illustrate that non-trophic indirect effects by overabundant deer on this perennial result in delayed female sex expression to unsustainably large plant sizes and leads to more pronounced plant shrinkage following female sex expression, effectively increasing the cost of reproduction. Among plants of reproductive age, increased deer impact decreases the size-dependent probability of flowering and reduces reproductive consistency over time. This pattern in sex expression skews populations toward female-biased OSRs at low deer impact sites and male-biased OSRs at intermediate and high deer impact sites. While this shift toward a male-biased OSR may ameliorate pollen limitation, it also decreases the effective population size when coupled with increased asexual reproduction. The divergence of reproductive strategies and reduced lifetime fitness in response to indirect deer impacts illustrate the persistent long-term effects of overabundant herbivores on unpalatable understory perennials.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 12 Sep 2019 05:00:00 GMT “Evolutionary rescue from a wave of biological invasion depends strongly on competitive mode” https://amnat.org/an/newpapers/Jan-Van-Dyken-A.html J. David Van Dyken (Jan 2020) Read the Article (Just Accepted) Can evolution save a species from being wiped out by an invasive species? Abstract Evolution can potentially rescue populations from being driven extinct by biological invasions, but predictions for this occurrence are generally lacking. Here I derive theoretical predictions for evolutionary rescue of a resident population experiencing invasion from an introduced competitor that spreads over its introduced range as a traveling spatial wave that displaces residents. I compare the likelihood of evolutionary rescue from invasion for two modes of competition: exploitation and interference competition. I find that, all else equal, evolutionary rescue is less effective at preventing extinction caused by interference-driven invasions than by exploitation-driven invasions. Rescue from interference-driven invasions is, surprisingly, independent of invader dispersal rate or the speed of invasion, and is more weakly dependent on range size than in the exploitation-driven case. In contrast, rescue from exploitation-driven invasions strongly depends on range size and is less likely during fast invasions. The results presented here have potential applications for conserving endemic species from non-native invaders, or ensuring extinction of pests using intentionally introduced biocontrol agents. More forthcoming papers &raquo; <p>J. David Van Dyken (Jan 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/706181">Read the Article</a></i> (Just Accepted) </p> <p><b>Can evolution save a species from being wiped out by an invasive species? </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>volution can potentially rescue populations from being driven extinct by biological invasions, but predictions for this occurrence are generally lacking. Here I derive theoretical predictions for evolutionary rescue of a resident population experiencing invasion from an introduced competitor that spreads over its introduced range as a traveling spatial wave that displaces residents. I compare the likelihood of evolutionary rescue from invasion for two modes of competition: exploitation and interference competition. I find that, all else equal, evolutionary rescue is less effective at preventing extinction caused by interference-driven invasions than by exploitation-driven invasions. Rescue from interference-driven invasions is, surprisingly, independent of invader dispersal rate or the speed of invasion, and is more weakly dependent on range size than in the exploitation-driven case. In contrast, rescue from exploitation-driven invasions strongly depends on range size and is less likely during fast invasions. The results presented here have potential applications for conserving endemic species from non-native invaders, or ensuring extinction of pests using intentionally introduced biocontrol agents. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 11 Sep 2019 05:00:00 GMT “Combined effects of natural enemies and competition for resources on a forest defoliator: a theoretical and empirical analysis” https://amnat.org/an/newpapers/Dec-Gallagher.html Molly E. Gallagher and Greg Dwyer (Dec 2019)Read the Article (Just Accepted) Resource competition & parasitoids drive budworm outbreaks in jack pine forests; climate change may upend the ecosystem Insect outbreaks can quickly damage or destroy thousands of acres of forests. Jack pine forests are frequently attacked by a species of very hungry caterpillar called the jack pine budworm. Jack pine budworm outbreaks occur every 6-12 years and continue for 2-4 years. Molly Gallagher and Greg Dwyer asked why these outbreaks happen, what causes them to end, and whether outbreaks might become more severe in the future as climate change progresses and the frequency of forest fires increases. To understand the factors that determine budworm survival, Molly Gallagher and Greg Dwyer constructed mathematical models that included different ecological effects and interactions. To estimate model parameters, they collected data from budworm outbreaks in jack pine forests in Wisconsin and Michigan from 2012-2015. They measured the density of budworm caterpillars in different parts of the forest over time, and recorded the size and age of trees that were under attack. They also raised caterpillars in the lab to determine how many were infected with parasitoids such as wasps or flies, which lay their eggs inside their caterpillar hosts, and eventually kill their hosts. By using their data to choose the best model, Dwyer and Gallagher showed that to best understand patterns of insect outbreaks, it is necessary to consider the effects of both parasitoid attacks and resource competition. At lower budworm densities, parasitoid attacks are more important, but when budworm density is very high, more caterpillars die due to a lack of plant resources. Simulations of a model including both of these factors result in realistic cycles of the budworm population. In future work, the researchers plan to extend their model to include the interacting effects of climate variables and fire frequency on forest health. Jack pine forests are a major component of the North American landscape, and with changing pressures from insect outbreaks and climate stressors, their future remains uncertain. Abstract Explanations for the dynamics of insect outbreaks often focus on natural enemies, on the grounds that parasitoid and pathogen attack rates are high during outbreaks. While natural enemy models can successfully reproduce outbreak cycles, experiments have repeatedly demonstrated the importance of resource quality and abundance. Experiments, however, are rarely invoked in modeling studies. Here we combine mechanistic models, observational data, and field experiments to quantify the roles of parasitoid attacks and resource competition on the jack pine budworm, Choristoneura pinus. By fitting models to a combination of observational and experimental data, we show that parasitoid attacks are the main source of larval budworm mortality at low and intermediate budworm densities, but that resource competition is the main source of mortality at high densities. Our results further show that the effects of resource competition become more severe with increasing host tree age, and that the effects of parasitoids are moderated by strong competition between parasitoids for hosts. Allowing for these effects in a model of insect outbreaks leads to realistic outbreak cycles, while a host-parasitoid model without resource competition produces an unrealistic stable equilibrium. The effects of resource competition are modulated by tree age, which in turn depends on fire regimes. Our model therefore suggests that increases in fire frequency due to climate change may interact in complex ways with budworm outbreaks. Our work shows that resource competition can be as important as natural enemies in modulating insect outbreaks, while demonstrating the usefulness of high-performance computing in experimental field ecology. More forthcoming papers &raquo; <p>Molly E. Gallagher and Greg Dwyer (Dec 2019)</p><p><i><a href="https://dx.doi.org/10.1086/705940">Read the Article</a></i> (Just Accepted) </p> <p><b>Resource competition & parasitoids drive budworm outbreaks in jack pine forests; climate change may upend the ecosystem </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>nsect outbreaks can quickly damage or destroy thousands of acres of forests. Jack pine forests are frequently attacked by a species of very hungry caterpillar called the jack pine budworm. Jack pine budworm outbreaks occur every 6-12 years and continue for 2-4 years. Molly Gallagher and Greg Dwyer asked why these outbreaks happen, what causes them to end, and whether outbreaks might become more severe in the future as climate change progresses and the frequency of forest fires increases. </p><p>To understand the factors that determine budworm survival, Molly Gallagher and Greg Dwyer constructed mathematical models that included different ecological effects and interactions. To estimate model parameters, they collected data from budworm outbreaks in jack pine forests in Wisconsin and Michigan from 2012-2015. They measured the density of budworm caterpillars in different parts of the forest over time, and recorded the size and age of trees that were under attack. They also raised caterpillars in the lab to determine how many were infected with parasitoids such as wasps or flies, which lay their eggs inside their caterpillar hosts, and eventually kill their hosts. </p><p>By using their data to choose the best model, Dwyer and Gallagher showed that to best understand patterns of insect outbreaks, it is necessary to consider the effects of both parasitoid attacks and resource competition. At lower budworm densities, parasitoid attacks are more important, but when budworm density is very high, more caterpillars die due to a lack of plant resources. Simulations of a model including both of these factors result in realistic cycles of the budworm population. </p><p>In future work, the researchers plan to extend their model to include the interacting effects of climate variables and fire frequency on forest health. Jack pine forests are a major component of the North American landscape, and with changing pressures from insect outbreaks and climate stressors, their future remains uncertain. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>xplanations for the dynamics of insect outbreaks often focus on natural enemies, on the grounds that parasitoid and pathogen attack rates are high during outbreaks. While natural enemy models can successfully reproduce outbreak cycles, experiments have repeatedly demonstrated the importance of resource quality and abundance. Experiments, however, are rarely invoked in modeling studies. Here we combine mechanistic models, observational data, and field experiments to quantify the roles of parasitoid attacks and resource competition on the jack pine budworm, <i>Choristoneura pinus</i>. By fitting models to a combination of observational and experimental data, we show that parasitoid attacks are the main source of larval budworm mortality at low and intermediate budworm densities, but that resource competition is the main source of mortality at high densities. Our results further show that the effects of resource competition become more severe with increasing host tree age, and that the effects of parasitoids are moderated by strong competition between parasitoids for hosts. Allowing for these effects in a model of insect outbreaks leads to realistic outbreak cycles, while a host-parasitoid model without resource competition produces an unrealistic stable equilibrium. The effects of resource competition are modulated by tree age, which in turn depends on fire regimes. Our model therefore suggests that increases in fire frequency due to climate change may interact in complex ways with budworm outbreaks. Our work shows that resource competition can be as important as natural enemies in modulating insect outbreaks, while demonstrating the usefulness of high-performance computing in experimental field ecology. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 22 Aug 2019 05:00:00 GMT “A Grinnellian niche perspective on species-area relationships” https://amnat.org/an/newpapers/Dec-Soberon.html Jorge Soberon (Dec 2019)Read the Article (Just Accepted) The species-area relationship is re-interpreted using fundamental niche positions in niche space: This is a new approach Ecologists have known for a very long time that there is a positive relationship between the size of a region and the number of species it contains. The relationship is often modeled using a very simple power law, with two parameters, and much work has been done on explaining these from demographic processes. In this work I attempt an alternative explanation, one based on the distribution of fundamental niches in environmental space. When area grows, the size of available environmental space also increases. This in turn means that the fundamental niches (ranges of environmental tolerances) of more species are included in the larger environmental space. Approaching the species-area relationship in this way is novel and illuminating. It shifts the focus from very local ecological processes to broad-scale climatic and biographical processes. Probably both perspectives will be needed for a comprehensive understanding of the problem. Abstract In this work, Grinnellian niche theory (a body of theory about geographic distributions of species in terms of non-interacting niche variables) is used to demonstrate that species-area relationships emerge with both size of environmental space and size of geographic area. As environmental space increases, more species' fundamental niches are included, thus increasing the number of species capable of living in the corresponding region. This idea is made operational by proposing a size measure for multidimensional environmental space and approximating fundamental niches with minimum-volume ellipsoids. This framework allows estimating a presence-absence matrix based on the distribution of fundamental niches in environmental space, from which many biodiversity measures can be calculated, such as beta diversity. I establish that Whittaker’s equation for beta diversity is equivalent to MacArthur’s formula relating species numbers and niche breadth; this latter equation provides a mechanism for the species niche-space relationship. I illustrate the theoretical results via exploration of niches of the terrestrial mammals of North America (north of Panama). Each world region has a unique structure of its environmental space, and the position of fundamental niches in niche space is different for different clades; therefore, species-area relationships depend on the clades involved and the region of focus, mostly as a function of MacArthur’s niche beta diversity. Analyzing species-area relationships from the perspective of niche position in environmental space is novel, shifting emphasis from demographic processes to historical, geographic, and climatic factors; moreover, the Grinnellian approach is based on available data and is computationally feasible. More forthcoming papers &raquo; <p>Jorge Soberon (Dec 2019)</p><p><i><a href="https://dx.doi.org/10.1086/705898">Read the Article</a></i> (Just Accepted) </p> <p><b>The species-area relationship is re-interpreted using fundamental niche positions in niche space: This is a new approach </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>cologists have known for a very long time that there is a positive relationship between the size of a region and the number of species it contains. The relationship is often modeled using a very simple power law, with two parameters, and much work has been done on explaining these from demographic processes. In this work I attempt an alternative explanation, one based on the distribution of fundamental niches in environmental space. When area grows, the size of available environmental space also increases. This in turn means that the fundamental niches (ranges of environmental tolerances) of more species are included in the larger environmental space. Approaching the species-area relationship in this way is novel and illuminating. It shifts the focus from very local ecological processes to broad-scale climatic and biographical processes. Probably both perspectives will be needed for a comprehensive understanding of the problem.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n this work, Grinnellian niche theory (a body of theory about geographic distributions of species in terms of non-interacting niche variables) is used to demonstrate that species-area relationships emerge with both size of environmental space and size of geographic area. As environmental space increases, more species' fundamental niches are included, thus increasing the number of species capable of living in the corresponding region. This idea is made operational by proposing a size measure for multidimensional environmental space and approximating fundamental niches with minimum-volume ellipsoids. This framework allows estimating a presence-absence matrix based on the distribution of fundamental niches in environmental space, from which many biodiversity measures can be calculated, such as beta diversity. I establish that Whittaker’s equation for beta diversity is equivalent to MacArthur’s formula relating species numbers and niche breadth; this latter equation provides a mechanism for the species niche-space relationship. I illustrate the theoretical results via exploration of niches of the terrestrial mammals of North America (north of Panama). Each world region has a unique structure of its environmental space, and the position of fundamental niches in niche space is different for different clades; therefore, species-area relationships depend on the clades involved and the region of focus, mostly as a function of MacArthur’s niche beta diversity. Analyzing species-area relationships from the perspective of niche position in environmental space is novel, shifting emphasis from demographic processes to historical, geographic, and climatic factors; moreover, the Grinnellian approach is based on available data and is computationally feasible. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 22 Aug 2019 05:00:00 GMT “Trade-offs in cold-resistance at the northern range edge of the common woodland ant <i>Aphaenogaster picea</i> (Formicidae)” https://amnat.org/an/newpapers/Dec-Nguyen-A.html Andrew D. Nguyen, Megan Brown, Jordan Zitnay, Sara Helms Cahan, Nicholas J. Gotelli, Amy Arnett, and Aaron M. Ellison (Dec 2019) Read the Article (Just Accepted)Abstract Geographic variation in low temperatures at poleward range margins of terrestrial species often mirrors population variation in cold resistance, suggesting that range boundaries may be set by evolutionary constraints on cold physiology. The northeastern woodland ant Aphaenogaster picea occurs up to approximately 45°N in central Maine. We combined presence-absence surveys with regression-tree analysis to characterize its northern range limit and assayed two measures of cold resistance operating on different timescales to determine whether and how marginal populations adapt to environmental extremes. The range boundary of A.&nbsp;picea was predicted primarily by temperature, but low winter temperatures did not emerge as the primary correlate of species occurrence. Low summer temperatures and high seasonal variability predicted absence above the boundary, whereas high mean annual temperature (MAT) predicted presence in southern Maine. In contrast, assays of cold resistance across multiple sites were consistent with the hypothesis of local cold adaptation at the range edge: among populations, there was a 4-minute reduction in Chill-Coma Recovery Time across a 2-degree reduction in MAT. Baseline resistance and capacity for additional plastic cold hardening shifted in opposite directions, with hardening capacity approaching zero at the coldest sites. This trade-off between baseline resistance and cold hardening capacity suggests that populations at range edges may adapt to colder temperatures through genetic assimilation of plastic responses, potentially constraining further adaptation and range expansion. More forthcoming papers &raquo; <p>Andrew D. Nguyen, Megan Brown, Jordan Zitnay, Sara Helms Cahan, Nicholas J. Gotelli, Amy Arnett, and Aaron M. Ellison (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705939">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>eographic variation in low temperatures at poleward range margins of terrestrial species often mirrors population variation in cold resistance, suggesting that range boundaries may be set by evolutionary constraints on cold physiology. The northeastern woodland ant <i>Aphaenogaster picea</i> occurs up to approximately 45°N in central Maine. We combined presence-absence surveys with regression-tree analysis to characterize its northern range limit and assayed two measures of cold resistance operating on different timescales to determine whether and how marginal populations adapt to environmental extremes. The range boundary of <i>A.&nbsp;picea</i> was predicted primarily by temperature, but low winter temperatures did not emerge as the primary correlate of species occurrence. Low summer temperatures and high seasonal variability predicted absence above the boundary, whereas high mean annual temperature (MAT) predicted presence in southern Maine. In contrast, assays of cold resistance across multiple sites were consistent with the hypothesis of local cold adaptation at the range edge: among populations, there was a 4-minute reduction in Chill-Coma Recovery Time across a 2-degree reduction in MAT. Baseline resistance and capacity for additional plastic cold hardening shifted in opposite directions, with hardening capacity approaching zero at the coldest sites. This trade-off between baseline resistance and cold hardening capacity suggests that populations at range edges may adapt to colder temperatures through genetic assimilation of plastic responses, potentially constraining further adaptation and range expansion. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 22 Aug 2019 05:00:00 GMT “Larger genomes linked to slower development and loss of late-developing traits” https://amnat.org/an/newpapers/Dec-Womack.html Molly C. Womack, Marissa J. Metz, and Kim L. Hoke (Dec 2019) Read the Article Larger genomes linked to slower development and loss of late-developing traits Genome size (the amount of DNA in an animal) varies widely among animals and can affect an animal’s appearance, how they develop, and how their bodies function. For example, increases in genome size have been linked with loss of toes in salamanders. Recently, researchers from Colorado State University were able to show that frogs with larger genomes take longer to develop from a swimming tadpole into a hopping froglet and often lack a middle ear bone as adults. The authors suggest that larger genomes, slower development, and smaller body sizes at the transition from tadpole to froglet (metamorphosis) may contribute to more than 39 mysterious losses of the middle ear among frog lineages. In amphibians more broadly, genome size is hypothesized to affect the formation of structures (bones, muscle, and other tissues) that appear late in development, closer to adulthood. However, few studies have linked larger genome size with changes in late-forming structures, especially outside of salamanders, which have much larger genomes than most animals. This new finding from Womack et al., appearing in The&nbsp;American Naturalist, concludes that increases in frog genome size, although less drastic than in salamanders, may affect development of late-forming traits such as middle ear bones. These results raise the possibility that the development of structures in other animals may be affected by changes in genome size. Abstract Genome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel dataset with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear. We established that genome size is negatively correlated with development rate across 90 anuran species and found that genome size evolution is correlated with evolutionary loss of the middle ear bone (columella) among 241 species (224 eared and 17 earless). We further tested whether the development of the tympanic middle ear could be constrained by large cell sizes and small body sizes during key stages of tympanic middle ear development (metamorphosis). Together, our evidence suggests that larger genomes, slower development rate, and smaller body sizes at metamorphosis may contribute to the loss of the anuran tympanic middle ear. We conclude that increases in anuran genome size, although less drastic than in salamanders, may affect development of late-forming traits. More forthcoming papers &raquo; <p>Molly C. Womack, Marissa J. Metz, and Kim L. Hoke (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705897">Read the Article</a></i></p> <p><b>Larger genomes linked to slower development and loss of late-developing traits </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>enome size (the amount of DNA in an animal) varies widely among animals and can affect an animal&rsquo;s appearance, how they develop, and how their bodies function. For example, increases in genome size have been linked with loss of toes in salamanders. Recently, researchers from Colorado State University were able to show that frogs with larger genomes take longer to develop from a swimming tadpole into a hopping froglet and often lack a middle ear bone as adults. The authors suggest that larger genomes, slower development, and smaller body sizes at the transition from tadpole to froglet (metamorphosis) may contribute to more than 39 mysterious losses of the middle ear among frog lineages. In amphibians more broadly, genome size is hypothesized to affect the formation of structures (bones, muscle, and other tissues) that appear late in development, closer to adulthood. However, few studies have linked larger genome size with changes in late-forming structures, especially outside of salamanders, which have much larger genomes than most animals. This new finding from Womack et al., appearing in <i>The&nbsp;American Naturalist</i>, concludes that increases in frog genome size, although less drastic than in salamanders, may affect development of late-forming traits such as middle ear bones. These results raise the possibility that the development of structures in other animals may be affected by changes in genome size.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>enome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel dataset with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear. We established that genome size is negatively correlated with development rate across 90 anuran species and found that genome size evolution is correlated with evolutionary loss of the middle ear bone (columella) among 241 species (224 eared and 17 earless). We further tested whether the development of the tympanic middle ear could be constrained by large cell sizes and small body sizes during key stages of tympanic middle ear development (metamorphosis). Together, our evidence suggests that larger genomes, slower development rate, and smaller body sizes at metamorphosis may contribute to the loss of the anuran tympanic middle ear. We conclude that increases in anuran genome size, although less drastic than in salamanders, may affect development of late-forming traits.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 22 Aug 2019 05:00:00 GMT