ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Thu, 21 Feb 2019 06:00:00 GMT 60 Links to the ASN Policy Statements https://amnat.org/announcements/Policy.html Letter to Secretary Azar on the Scientific Understanding of Sex and Gender Joint Societies Letter to the EPA on Using All Available Data Letter to the NSF about the Doctoral Dissertation Improvement Grant Program ASN Attends Congressional Visits Day 2017 Letter to the U.S. Congress on the Endangered Species Act Letter to the U.S. Congress on Plant Conservation Legislation Joint Societies&#39; Letter to the Trump Administration on Travel Restrictions Letter to the US Congress on Proposed Tax Cuts and Jobs Act Contact asnpresident@gmail.com The committee often works in coordination with the Public Policy Committee of the Society for the Study of Evolution: http://www.evolutionsociety.org/content/policy.html <ul> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/LTRgender.html">Letter to Secretary Azar on the Scientific Understanding of Sex and Gender</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/LTREPA.html">Joint Societies Letter to the EPA on Using All Available Data</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/LTRDDIG.html">Letter to the NSF about the Doctoral Dissertation Improvement Grant Program</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/ReportAIBS.html">ASN Attends Congressional Visits Day 2017</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/LTRspecies.html">Letter to the U.S. Congress on the Endangered Species Act</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/LTRplant.html">Letter to the U.S. Congress on Plant Conservation Legislation</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://www.amnat.org/announcements/LTRvisa.html">Joint Societies&#39; Letter to the Trump Administration on Travel Restrictions</a></h2> </li> <li> <h2 style="margin: 0px; padding: 0px; font-size: 24px; color: rgb(0, 88, 37); font-family: Georgia, Georgia, &quot;Times New Roman&quot;, Times, serif; line-height: 31.2px; text-decoration: none; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(235, 253, 255);"><a href="https://amnat.org/announcements/LTRTuitionTax.html">Letter to the US Congress on Proposed Tax Cuts and Jobs Act</a></h2> </li> </ul><p><strong>Contact <a href="mailto:asnpresident@gmail.com">asnpresident@gmail.com</a></strong></p> <p>The committee often works in coordination with the Public Policy Committee of the Society for the Study of Evolution: <a href="http://www.evolutionsociety.org/content/policy.html">http://www.evolutionsociety.org/content/policy.html</a></p> Mon, 18 Feb 2019 06:00:00 GMT 2019 Jasper Loftus-Hills Young Investigator Awards https://amnat.org/announcements/ANNwinYIA.html The American Society of Naturalist’s Young Investigator Award is in honor of Jasper Loftus-Hills, a young scientist who died tragically 3 years after receiving his PhD. This award goes to applicants who completed their PhD three years preceding the application deadline or are in their last year of a PhD program. Jeremy Fox, chair of the nominating committee, has written a blog about the experience. As he says, "The strength and diversity of the winners reflect the strength and diversity of the applicant pool, both in terms of their research areas and demographics." We are pleased to announce that this year’s recipients of the ASN Young Investiagor Awards are: &bull;&nbsp;&nbsp; &nbsp;Eleanor Caves: https://eleanorcaves.weebly.com/ &bull;&nbsp;&nbsp; &nbsp;Jean Philippe Gibert: https://jeanpgibert.weebly.com/ &bull;&nbsp;&nbsp; &nbsp;Ambika Kamath: https://ambikamath.wordpress.com/ &bull;&nbsp;&nbsp;&nbsp; Stilianos Louca:&nbsp;https://biology.uoregon.edu/profile/slouca/ We very much looking forward to their participation in the ASN YIA symposium at the annual meeting in Providence, Rhode Island, this summer. &nbsp; <p>The American Society of Naturalist&rsquo;s Young Investigator Award is in honor of Jasper Loftus-Hills, a young scientist who died tragically 3 years after receiving his PhD. This award goes to applicants who completed their PhD three years preceding the application deadline or are in their last year of a PhD program.</p> <p>Jeremy Fox, chair of the nominating committee, has <a href="https://dynamicecology.wordpress.com/2018/02/19/the-winners-of-the-asn-jasper-loftus-hills-young-investigator-awards-have-been-announced/">written a blog</a> about the experience. As he says, &quot;The strength and diversity of the winners reflect the strength and diversity of the applicant pool, both in terms of their research areas and demographics.&quot;</p> <p>We are pleased to announce that this year&rsquo;s recipients of the ASN Young Investiagor Awards are:</p> <p>&bull;&nbsp;&nbsp; &nbsp;Eleanor Caves: <a href="https://eleanorcaves.weebly.com/">https://eleanorcaves.weebly.com/</a><br /> &bull;&nbsp;&nbsp; &nbsp;Jean Philippe Gibert: <a href="https://jeanpgibert.weebly.com/">https://jeanpgibert.weebly.com/</a><br /> &bull;&nbsp;&nbsp; &nbsp;Ambika Kamath: <a href="https://ambikamath.wordpress.com/">https://ambikamath.wordpress.com/</a><br /> &bull;&nbsp;&nbsp;&nbsp; Stilianos Louca:&nbsp;<a href="https://biology.uoregon.edu/profile/slouca/">https://biology.uoregon.edu/profile/slouca/</a></p> <p>We very much looking forward to their participation in the ASN YIA symposium at the annual meeting in Providence, Rhode Island, this summer.</p> <p>&nbsp;</p> Mon, 18 Feb 2019 06:00:00 GMT “Revisiting a key innovation in evolutionary biology: Felsenstein’s ‘Phylogenies and the comparative method’” https://amnat.org/an/newpapers/JuneHuey.html The DOI will be https://dx.doi.org/10.1086/703055 We review how Felsenstein’s 1985 paper on phylogenies and the comparative method revolutionized evolutionary biology Abstract The comparative method has long been a fundamental exploratory tool in evolutionary biology, but this venerable approach was revolutionized in 1985, when Felsenstein published “Phylogenies and the Comparative Method” in The&nbsp;American Naturalist. This paper forced comparative biologists to start thinking phylogenetically when conducting statistical analyses of correlated trait evolution, rather than simply applying conventional statistical methods that ignore evolutionary relationships. It did so by introducing a novel analytical method (phylogenetically “independent contrasts”) that required a phylogenetic topology with branch lengths and that assumed a Brownian motion model of trait evolution. Independent contrasts enabled comparative biologists to avoid the statistical dilemma of non-independence of species values, arising from shared ancestry, but came at the cost of needing a detailed phylogeny and of accepting a specific model of character change. Nevertheless, this paper not only revitalized comparative biology, but even encouraged studies aimed at estimating phylogenies. Felsenstein’s characteristically lucid and concise statement of the problem (illustrated with powerful graphics), coupled with an oncoming flood of new molecular data and techniques for estimating phylogenies, led Felsenstein&nbsp;’85 to become the second most cited paper in the history of this journal. Here we present a personal review of comparative biology before, during, and after Joe’s paper. For historical context, we append a Perspective written by Joe himself (Appendix&nbsp;A, which describes how his paper evolved), unedited transcripts of reviews of his submitted manuscript (Appendix&nbsp;B), and a guide to some non-trivial calculations (Appendix&nbsp;C). These additional materials help emphasize that the process of science does not always occur gradually or predictably. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/703055 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/703055">Read the Article</a></i> </p> --> <p><b>We review how Felsenstein’s 1985 paper on phylogenies and the comparative method revolutionized evolutionary biology </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;">T</span>he comparative method has long been a fundamental exploratory tool in evolutionary biology, but this venerable approach was revolutionized in 1985, when Felsenstein published “Phylogenies and the Comparative Method” in <i>The&nbsp;American Naturalist</i>. This paper forced comparative biologists to start thinking phylogenetically when conducting statistical analyses of correlated trait evolution, rather than simply applying conventional statistical methods that ignore evolutionary relationships. It did so by introducing a novel analytical method (phylogenetically “independent contrasts”) that required a phylogenetic topology with branch lengths and that assumed a Brownian motion model of trait evolution. Independent contrasts enabled comparative biologists to avoid the statistical dilemma of non-independence of species values, arising from shared ancestry, but came at the cost of needing a detailed phylogeny and of accepting a specific model of character change. Nevertheless, this paper not only revitalized comparative biology, but even encouraged studies aimed at estimating phylogenies. Felsenstein’s characteristically lucid and concise statement of the problem (illustrated with powerful graphics), coupled with an oncoming flood of new molecular data and techniques for estimating phylogenies, led Felsenstein&nbsp;’85 to become the second most cited paper in the history of this journal. Here we present a personal review of comparative biology before, during, and after Joe’s paper. For historical context, we append a Perspective written by Joe himself (Appendix&nbsp;A, which describes how his paper evolved), unedited transcripts of reviews of his submitted manuscript (Appendix&nbsp;B), and a guide to some non-trivial calculations (Appendix&nbsp;C). These additional materials help emphasize that the process of science does not always occur gradually or predictably. </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, 14 Feb 2019 06:00:00 GMT “Trait-based modeling of multi-host pathogen transmission: Plant-pollinator networks” https://amnat.org/an/newpapers/JuneTruitt.html The DOI will be https://dx.doi.org/10.1086/701898 A new modeling approach for disease spread in plant-pollinator networks suggests new ideas for controlling bee diseases A&nbsp;bee visiting a flower to gather nectar might pick up an unwelcome extra: a virus (or another infectious disease organism) deposited there by a previous visitor. Because infectious disease is one of the factors implicated in recent declines of bees and other natural pollinators, there is increasing interest in finding practical ways to reduce the spread of these diseases. Mathematical models have often been helpful for identifying “disease hotspots” and designing effective disease control strategies in humans and wildlife. Disease spread in species-rich plant-pollinator interaction networks poses the challenge that a model describing each of the many distinct interactions (among multiple pollinator and flower species) would require an enormous number of parameters and an enormous amount of data to estimate those parameters. In a new paper in The American Naturalist, Truitt et al. propose an alternative trait-based approach to modeling disease spread in complex plant-pollinator networks. As one example, many such networks are “nested”: non-choosy pollinators visit all flowers, and more choosy ones visit smaller and smaller subsets of those visited by the less choosy. Truitt et al. model a nested network in terms of two traits: pollinator “choosiness” and flower “attractiveness”, where choosiness determines how much a pollinator concentrates on the more attractive flowers. Given the pollinator and flower trait distributions, one parameter (maximum choosiness) specifies the relative risk of disease spread in different interactions. Mathematical and computational studies of this model (mostly by Lauren Truitt and co-author Andrew Vaughn), and another where bees preferentially visit flowers of a size matching their own, demonstrate that the key interactions are those involving flowers visited out of proportion to their abundance, and pollinators which preferentially visit those flowers. This finding suggests strategies, based on feasible data gathering, to reduce disease spread by changing the abundances of different plant species. Such strategies could be implemented in wildflower plantings whose goal is to improve pollinator health. The paper is an extension of Truitt’s undergraduate honors thesis at Cornell (directed by co-authors McArt and Ellner), where she co-majored in biology and mathematics. Vaughn is currently a Cornell senior majoring in mathematics, and Truitt is interning at NIH. Abstract Epidemiological models for multi-host pathogen systems often classify individuals taxonomically and use species-specific parameter values, but in species-rich communities, that approach may require intractably many parameters. Trait-based epidemiological models offer a potential solution, but have not accounted for within-species trait variation or between-species trait overlap. Here, we propose and study trait-based models with host and vector communities represented as trait distributions without regard to species identity. To illustrate this approach, we develop SIS models for disease spread in plant-pollinator networks with continuous trait distributions. We model trait-dependent contact rates in two common scenarios: nested networks, and specialized plant-pollinator interactions based on trait matching. We find that disease spread in plant-pollinator networks is impacted the most by selective pollinators, universally attractive flowers, and co-specialized plant-pollinator pairs. When extreme pollinator traits are rare, pollinators with common traits are most important for disease spread, whereas when extreme flower traits are rare, flowers with uncommon traits impact disease spread the most. Greater nestedness and specialization both typically promote disease persistence. Given recent pollinator declines caused in part by pathogens, we discuss how trait-based models could inform conservation strategies for wild and managed pollinators. Furthermore, while we have applied our model to pollinators and pathogens, its framework is general and can be transferred to any kind of species interactions, in any community. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701898 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701898">Read the Article</a></i> </p> --> <p><b>A new modeling approach for disease spread in plant-pollinator networks suggests new ideas for controlling bee diseases </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;">A</span>&nbsp;bee visiting a flower to gather nectar might pick up an unwelcome extra: a virus (or another infectious disease organism) deposited there by a previous visitor. Because infectious disease is one of the factors implicated in recent declines of bees and other natural pollinators, there is increasing interest in finding practical ways to reduce the spread of these diseases. Mathematical models have often been helpful for identifying “disease hotspots” and designing effective disease control strategies in humans and wildlife. Disease spread in species-rich plant-pollinator interaction networks poses the challenge that a model describing each of the many distinct interactions (among multiple pollinator and flower species) would require an enormous number of parameters and an enormous amount of data to estimate those parameters. </p> <p>In a new paper in <i>The American Naturalist</i>, Truitt et al. propose an alternative trait-based approach to modeling disease spread in complex plant-pollinator networks. As one example, many such networks are “nested”: non-choosy pollinators visit all flowers, and more choosy ones visit smaller and smaller subsets of those visited by the less choosy. Truitt et al. model a nested network in terms of two traits: pollinator “choosiness” and flower “attractiveness”, where choosiness determines how much a pollinator concentrates on the more attractive flowers. Given the pollinator and flower trait distributions, one parameter (maximum choosiness) specifies the relative risk of disease spread in different interactions. Mathematical and computational studies of this model (mostly by Lauren Truitt and co-author Andrew Vaughn), and another where bees preferentially visit flowers of a size matching their own, demonstrate that the key interactions are those involving flowers visited out of proportion to their abundance, and pollinators which preferentially visit those flowers. This finding suggests strategies, based on feasible data gathering, to reduce disease spread by changing the abundances of different plant species. Such strategies could be implemented in wildflower plantings whose goal is to improve pollinator health.</p> <p>The paper is an extension of Truitt’s undergraduate honors thesis at Cornell (directed by co-authors McArt and Ellner), where she co-majored in biology and mathematics. Vaughn is currently a Cornell senior majoring in mathematics, and Truitt is interning at NIH. </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>pidemiological models for multi-host pathogen systems often classify individuals taxonomically and use species-specific parameter values, but in species-rich communities, that approach may require intractably many parameters. Trait-based epidemiological models offer a potential solution, but have not accounted for within-species trait variation or between-species trait overlap. Here, we propose and study trait-based models with host and vector communities represented as trait distributions without regard to species identity. To illustrate this approach, we develop SIS models for disease spread in plant-pollinator networks with continuous trait distributions. We model trait-dependent contact rates in two common scenarios: nested networks, and specialized plant-pollinator interactions based on trait matching. We find that disease spread in plant-pollinator networks is impacted the most by selective pollinators, universally attractive flowers, and co-specialized plant-pollinator pairs. When extreme pollinator traits are rare, pollinators with common traits are most important for disease spread, whereas when extreme flower traits are rare, flowers with uncommon traits impact disease spread the most. Greater nestedness and specialization both typically promote disease persistence. Given recent pollinator declines caused in part by pathogens, we discuss how trait-based models could inform conservation strategies for wild and managed pollinators. Furthermore, while we have applied our model to pollinators and pathogens, its framework is general and can be transferred to any kind of species interactions, in any community.</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, 14 Feb 2019 06:00:00 GMT “When do shifts in trait dynamics precede population declines?” https://amnat.org/an/newpapers/MayBaruah.html The DOI will be https://dx.doi.org/10.1086/702849 Shifts in fitness related traits could precede population decline, and is influenced by a host of eco-evo factors Predicting population declines in response to environmental change is an ongoing challenge in ecology. Recent studies suggest that predicting such rapid declines might be possible by monitoring statistical signals (called early warning signals, EWSs) embedded within abundance time series. Both theoretical and empirical studies have shown that before a population declines, EWSs, such as temporal variance and autocorrelation in abundance, increase over time. There are, however, potential pitfalls associated with such signals, including, but not limited to, the requirement of high-quality abundance time-series data. Alternatively, it is possible to strengthen these signals by incorporating information from the dynamics of physical traits such as body size. These trait-inclusive EWSs have been shown to improve our ability to predict population declines over abundance-based EWSs. However, under what environmental, ecological, and evolutionary circumstances it is useful to use traits as an indicator of population decline, is unknown. In a new study appearing in The&nbsp;American Naturalist, Gaurav Baruah, Christopher Clements, Frédéric Guillaume, and Arpat Ozgul develop a theoretical model to investigate the circumstances under which trait shifts can precede population declines, and thus can act as an early warning signal. They show, using model simulations and empirical data from an experimental microcosm, that under slow to medium environmental change scenarios, shifts in traits are more likely to precede population declines. They further demonstrate that reliable environmental cues, high net reproductive rate, high levels of plasticity and genetic variation lead to shifts in traits preceding population declines, even during fast changes in the environment. Their findings provide crucial information on when biodiversity monitoring programs can target trait dynamics as potential early warning signals of impending population declines. Abstract Predicting population responses to environmental change is an ongoing challenge in ecology. Studies investigating the links between fitness-related phenotypic traits and demography have shown that trait dynamic responses to environmental change can sometimes precede population dynamic responses, and thus, can be used as an early warning signal. However, it is still unknown under which ecological and evolutionary circumstances, shifts in fitness-related traits can precede population responses to environmental perturbation. Here, we take a trait-based demographic approach and investigate both trait and population dynamics in a density-regulated population in response to a gradual change in the environment. We explore the ecological and evolutionary constraints under which shifts in fitness-related trait precedes a decline in population size. We show both analytically and with experimental data that under medium-to-slow rate of environmental change, shifts in a trait value can precede population decline. We further show the positive influence of environmental predictability, net reproductive rate, plasticity, and genetic variation on shifts in trait dynamics preceding potential population declines. These results still hold under non-constant genetic variation and environmental stochasticity. Our study highlights ecological and evolutionary circumstances under which a fitness-related trait can be used as an early warning signal of an impending population decline. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702849 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702849">Read the Article</a></i> </p> --> <p><b>Shifts in fitness related traits could precede population decline, and is influenced by a host of eco-evo factors </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>redicting population declines in response to environmental change is an ongoing challenge in ecology. Recent studies suggest that predicting such rapid declines might be possible by monitoring statistical signals (called early warning signals, EWSs) embedded within abundance time series. Both theoretical and empirical studies have shown that before a population declines, EWSs, such as temporal variance and autocorrelation in abundance, increase over time. There are, however, potential pitfalls associated with such signals, including, but not limited to, the requirement of high-quality abundance time-series data. Alternatively, it is possible to strengthen these signals by incorporating information from the dynamics of physical traits such as body size. These trait-inclusive EWSs have been shown to improve our ability to predict population declines over abundance-based EWSs. However, under what environmental, ecological, and evolutionary circumstances it is useful to use traits as an indicator of population decline, is unknown.</p> <p>In a new study appearing in <i>The&nbsp;American Naturalist</i>, Gaurav Baruah, Christopher Clements, Frédéric Guillaume, and Arpat Ozgul develop a theoretical model to investigate the circumstances under which trait shifts can precede population declines, and thus can act as an early warning signal. They show, using model simulations and empirical data from an experimental microcosm, that under slow to medium environmental change scenarios, shifts in traits are more likely to precede population declines. They further demonstrate that reliable environmental cues, high net reproductive rate, high levels of plasticity and genetic variation lead to shifts in traits preceding population declines, even during fast changes in the environment. Their findings provide crucial information on when biodiversity monitoring programs can target trait dynamics as potential early warning signals of impending population declines.</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>redicting population responses to environmental change is an ongoing challenge in ecology. Studies investigating the links between fitness-related phenotypic traits and demography have shown that trait dynamic responses to environmental change can sometimes precede population dynamic responses, and thus, can be used as an early warning signal. However, it is still unknown under which ecological and evolutionary circumstances, shifts in fitness-related traits can precede population responses to environmental perturbation. Here, we take a trait-based demographic approach and investigate both trait and population dynamics in a density-regulated population in response to a gradual change in the environment. We explore the ecological and evolutionary constraints under which shifts in fitness-related trait precedes a decline in population size. We show both analytically and with experimental data that under medium-to-slow rate of environmental change, shifts in a trait value can precede population decline. We further show the positive influence of environmental predictability, net reproductive rate, plasticity, and genetic variation on shifts in trait dynamics preceding potential population declines. These results still hold under non-constant genetic variation and environmental stochasticity. Our study highlights ecological and evolutionary circumstances under which a fitness-related trait can be used as an early warning signal of an impending population decline. </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, 12 Feb 2019 06:00:00 GMT “Higher nest predation favors rapid fledging at the cost of plumage quality in nestling birds” https://amnat.org/an/newpapers/MayCallan.html The DOI will be https://dx.doi.org/10.1086/702856 Trade offs of rapid development are expressed in body feathers of birds Developing too quickly often forces organisms to compromise the quality of traits they grow. But which traits should express these compromises in quality the most? Some traits must be used for the entire life cycle (bones, organs, immune systems) while other traits can be repaired or replaced later in life (feathers, exoskeletons, fur). These differences in the duration that traits are used suggest that when rapid development forces organisms to compromise trait quality, traits used for short periods of time should suffer the greatest losses in quality compared to traits used for life. The authors explore this idea using body feathers that young birds grow while in the nest. For many species, these feathers are replaced shortly after leaving the nest, making them a short-lived trait. Species that grow and develop quickly show the greatest losses in nestling feather quality compared to species that develop more slowly. By contrast, adult survival probability across species shows no relationship with development speed. These contrasting findings between the quality of short-term traits like nestling feathers and long term traits like those important for adult survival, suggests that when organisms must develop rapidly, they compromise the quality of traits that can be repaired or replaced later in life. Abstract High predation risk can favor rapid offspring development at the expense of offspring quality. Impacts of rapid development on phenotypic quality should be most readily expressed in traits that minimize fitness costs. We hypothesize that ephemeral traits that are replaced or repaired after a short period of life might express trade-offs in quality as a result of rapid development more strongly than traits used throughout life. We explored this idea for plumage quality in nestling body feathers, an ephemeral trait. We found a strong trade-off whereby nestlings that spend less time in the nest produced lower quality plumage with less dense barbs relative to adults across 123 temperate and tropical species. For a subset of these species (n=67), we found that variation in the risk of nest predation explained additional variation in plumage quality beyond development time. Ultimately, the fitness costs of a poor quality ephemeral trait, like nestling body feathers, may be outweighed by the fitness benefits of shorter development times that reduce predation risk. At the same time, reduced resource allocation to traits with small fitness costs, like ephemeral traits, may ameliorate resource constraints from rapid development on traits with larger fitness impacts. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702856 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702856">Read the Article</a></i> </p> --> <p><b>Trade offs of rapid development are expressed in body feathers of birds </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;">D</span>eveloping too quickly often forces organisms to compromise the quality of traits they grow. But which traits should express these compromises in quality the most? Some traits must be used for the entire life cycle (bones, organs, immune systems) while other traits can be repaired or replaced later in life (feathers, exoskeletons, fur). These differences in the duration that traits are used suggest that when rapid development forces organisms to compromise trait quality, traits used for short periods of time should suffer the greatest losses in quality compared to traits used for life. </p> <p>The authors explore this idea using body feathers that young birds grow while in the nest. For many species, these feathers are replaced shortly after leaving the nest, making them a short-lived trait. Species that grow and develop quickly show the greatest losses in nestling feather quality compared to species that develop more slowly. By contrast, adult survival probability across species shows no relationship with development speed. These contrasting findings between the quality of short-term traits like nestling feathers and long term traits like those important for adult survival, suggests that when organisms must develop rapidly, they compromise the quality of traits that can be repaired or replaced later in life.</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;">H</span>igh predation risk can favor rapid offspring development at the expense of offspring quality. Impacts of rapid development on phenotypic quality should be most readily expressed in traits that minimize fitness costs. We hypothesize that ephemeral traits that are replaced or repaired after a short period of life might express trade-offs in quality as a result of rapid development more strongly than traits used throughout life. We explored this idea for plumage quality in nestling body feathers, an ephemeral trait. We found a strong trade-off whereby nestlings that spend less time in the nest produced lower quality plumage with less dense barbs relative to adults across 123 temperate and tropical species. For a subset of these species (<i>n</i>=67), we found that variation in the risk of nest predation explained additional variation in plumage quality beyond development time. Ultimately, the fitness costs of a poor quality ephemeral trait, like nestling body feathers, may be outweighed by the fitness benefits of shorter development times that reduce predation risk. At the same time, reduced resource allocation to traits with small fitness costs, like ephemeral traits, may ameliorate resource constraints from rapid development on traits with larger fitness impacts. </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, 12 Feb 2019 06:00:00 GMT “Predicting the thermal and allometric dependencies of disease transmission via the metabolic theory of ecology” https://amnat.org/an/newpapers/MayKirk.html Warming temperatures associated with climate change and host body size can both alter infectious disease spread, though often in complex ways. This is because both factors can affect different components of disease transmission, namely the contact rate between uninfected and infected individuals or parasites, and the subsequent likelihood that that contact results in a new infection. To understand how warming and size will affect disease spread in a host-parasite system, we need to first predict their effects on contact and infection rates, and then tie these predictions together using classic disease models of transmission. The metabolic theory of ecology (MTE) provides a general framework for predicting how temperature and host size affect contact and infection rates. Here, the authors conducted two experiments using a Daphnia–parasite system, and then fit MTE models to the data. They show that transmission is strongly affected by temperature, and that the different rates vary with temperature and body size in distinct manners. Moreover, they show that MTE functions can capture how contact rate and the probability of infection change across temperature and size. Together these two functions can accurately predict transmission rate continuously across a wide temperature range. This represents a valuable potential tool for helping predict how disease spread will change as environmental temperatures rise. Abstract The metabolic theory of ecology (MTE) provides a general framework of allometric and thermal dependence that may be useful for predicting how climate change will affect disease spread. Using Daphnia magna and a microsporidian gut parasite, we conducted two experiments across a wide thermal range and fitted transmission models that utilize MTE submodels for transmission parameters. We decomposed transmission into contact rate and probability of infection, and further decomposed probability of infection into a product of gut residence time (GRT) and per-parasite infection rate of gut cells. Contact rate generally increased with temperature and scaled positively with body size, whereas infection rate had a narrow hump-shaped thermal response and scaled negatively with body size. GRT increased with host size and was longest at extreme temperatures. GRT and infection rate inside the gut combined to create a 3.5× higher probability of infection for the smallest relative to the largest individuals. Small temperature changes caused large differences in transmission. We also fit several alternative transmission models to data at individual temperatures. The more complex models, parasite antagonism or synergism and host heterogeneity, did not substantially improve the fit to the data. Our results show that transmission rate is the product of several distinct thermal and allometric functions that can be predicted continuously across temperature and host size using MTE. More forthcoming papers &raquo; <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>arming temperatures associated with climate change and host body size can both alter infectious disease spread, though often in complex ways. This is because both factors can affect different components of disease transmission, namely the contact rate between uninfected and infected individuals or parasites, and the subsequent likelihood that that contact results in a new infection. To understand how warming and size will affect disease spread in a host-parasite system, we need to first predict their effects on contact and infection rates, and then tie these predictions together using classic disease models of transmission. The metabolic theory of ecology (MTE) provides a general framework for predicting how temperature and host size affect contact and infection rates. Here, the authors conducted two experiments using a <i>Daphnia</i>–parasite system, and then fit MTE models to the data. They show that transmission is strongly affected by temperature, and that the different rates vary with temperature and body size in distinct manners. Moreover, they show that MTE functions can capture how contact rate and the probability of infection change across temperature and size. Together these two functions can accurately predict transmission rate continuously across a wide temperature range. This represents a valuable potential tool for helping predict how disease spread will change as environmental temperatures rise.</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>he metabolic theory of ecology (MTE) provides a general framework of allometric and thermal dependence that may be useful for predicting how climate change will affect disease spread. Using <i>Daphnia magna</i> and a microsporidian gut parasite, we conducted two experiments across a wide thermal range and fitted transmission models that utilize MTE submodels for transmission parameters. We decomposed transmission into contact rate and probability of infection, and further decomposed probability of infection into a product of gut residence time (GRT) and per-parasite infection rate of gut cells. Contact rate generally increased with temperature and scaled positively with body size, whereas infection rate had a narrow hump-shaped thermal response and scaled negatively with body size. GRT increased with host size and was longest at extreme temperatures. GRT and infection rate inside the gut combined to create a 3.5× higher probability of infection for the smallest relative to the largest individuals. Small temperature changes caused large differences in transmission. We also fit several alternative transmission models to data at individual temperatures. The more complex models, parasite antagonism or synergism and host heterogeneity, did not substantially improve the fit to the data. Our results show that transmission rate is the product of several distinct thermal and allometric functions that can be predicted continuously across temperature and host size using MTE. </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, 06 Feb 2019 06:00:00 GMT “Sexually antagonistic variation and the evolution of dimorphic sexual systems” https://amnat.org/an/newpapers/MayOlito.html The DOI will be https://dx.doi.org/10.1086/702847 Sexually antagonistic variation promotes the evolution of separate sexes from hermaphroditism beyond classic predictions Understanding when and why separate sexes (dioecy) evolve from hermaphroditism is a fundamental question in evolutionary biology with a long and storied history. A key advance came in the late 1970’s, when Brian and Deborah Charlesworth developed a series of theoretical models, published here in The&nbsp;American Naturalist, describing the evolution of separate sexes from hermaphroditism via the invasion of nuclear unisexual sterility alleles, which abolish either the male or female sex-function in hermaphrodites (Charlesworth & Charlesworth 1978). This influential theory predicts that the evolution of separates sexes is most likely when female and male sex-functions genetically trade-off with one another, and rates of self-fertilization and inbreeding depression are high among hermaphrodites. Yet, while some studies of single species support this longstanding prediction, empirical evidence for an association between dioecy and selfing across taxa remains underwhelming. In their forthcoming article, Colin Olito and Tim Connallon reconsider this issue, extending the theory with a series of two-locus models involving both a ‘sterility locus’ (where a unisexual sterility mutation may occur), and another ‘sexually antagonistic locus’ (where alleles beneficial for one sex function are deleterious for the other). Their models show that genetic linkage of unisexual sterility alleles to a sexually antagonistic locus facilitates the initial step in the evolution of separate sexes and inverts the predicted relation between self-fertilization and dioecy relative to the predictions of the classical theory by essentially allowing unisexual sterility alleles to ‘hitchhike’ with SA alleles. Their findings suggest that dioecy may evolve from hermaphroditism under much broader conditions than previously thought and suggest a new role for sexually antagonistic genetic variation in the evolutionary origins of new sex-chromosome systems. References Charlesworth, B., and D. Charlesworth. 1978. A model for the evolution of dioecy and gynodioecy. The&nbsp;American Naturalist 112:975–997.Abstract Multicellular Eukaryotes use a broad spectrum of sexual reproduction strategies, ranging from simultaneous hermaphroditism to complete dioecy (separate sexes). The evolutionary pathway from hermaphroditism to dioecy involves the spread of “sterility alleles” that eliminate female or male reproductive functions, producing unisexual individuals. Classical theory predicts that evolutionary transitions to dioecy are feasible when female and male sex functions genetically trade-off with one another (allocation to sex functions is “sexually antagonistic”), and rates of self-fertilization and inbreeding depression are high within the ancestral hermaphrodite population. We show that genetic linkage between sterility alleles and loci under sexually antagonistic selection significantly alters these classical predictions. We identify three specific consequences of linkage for the evolution of dimorphic sexual systems. First, linkage broadens conditions for the invasion of unisexual sterility alleles, facilitating transitions to sexual systems that are intermediate between hermaphroditism and dioecy (andro- and gynodioecy). Second, linkage elevates the equilibrium frequencies of unisexual individuals within andro- and gynodioecious populations, which promotes subsequent transitions to full dioecy. Third, linkage dampens the role of inbreeding during transitions to andro- and gynodioecy, making these transitions feasible in outbred populations. We discuss implications of these results for the evolution of dimorphic reproductive systems and sex chromosomes. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702847 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702847">Read the Article</a></i> </p> --> <p><b>Sexually antagonistic variation promotes the evolution of separate sexes from hermaphroditism beyond classic predictions </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;">U</span>nderstanding when and why separate sexes (dioecy) evolve from hermaphroditism is a fundamental question in evolutionary biology with a long and storied history. A key advance came in the late 1970&rsquo;s, when Brian and Deborah Charlesworth developed a series of theoretical models, published here in <i>The&nbsp;American Naturalist</i>, describing the evolution of separate sexes from hermaphroditism via the invasion of nuclear unisexual sterility alleles, which abolish either the male or female sex-function in hermaphrodites (Charlesworth &amp; Charlesworth 1978). This influential theory predicts that the evolution of separates sexes is most likely when female and male sex-functions genetically trade-off with one another, and rates of self-fertilization and inbreeding depression are high among hermaphrodites. Yet, while some studies of single species support this longstanding prediction, empirical evidence for an association between dioecy and selfing across taxa remains underwhelming. In their forthcoming article, Colin Olito and Tim Connallon reconsider this issue, extending the theory with a series of two-locus models involving both a &lsquo;sterility locus&rsquo; (where a unisexual sterility mutation may occur), and another &lsquo;sexually antagonistic locus&rsquo; (where alleles beneficial for one sex function are deleterious for the other). Their models show that genetic linkage of unisexual sterility alleles to a sexually antagonistic locus facilitates the initial step in the evolution of separate sexes and inverts the predicted relation between self-fertilization and dioecy relative to the predictions of the classical theory by essentially allowing unisexual sterility alleles to &lsquo;hitchhike&rsquo; with SA alleles. Their findings suggest that dioecy may evolve from hermaphroditism under much broader conditions than previously thought and suggest a new role for sexually antagonistic genetic variation in the evolutionary origins of new sex-chromosome systems.</p> <h4>References</h4> <p>Charlesworth, B., and D. Charlesworth. 1978. A model for the evolution of dioecy and gynodioecy. <i>The&nbsp;American Naturalist</i> 112:975&ndash;997.</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;">M</span>ulticellular Eukaryotes use a broad spectrum of sexual reproduction strategies, ranging from simultaneous hermaphroditism to complete dioecy (separate sexes). The evolutionary pathway from hermaphroditism to dioecy involves the spread of “sterility alleles” that eliminate female or male reproductive functions, producing unisexual individuals. Classical theory predicts that evolutionary transitions to dioecy are feasible when female and male sex functions genetically trade-off with one another (allocation to sex functions is “sexually antagonistic”), and rates of self-fertilization and inbreeding depression are high within the ancestral hermaphrodite population. We show that genetic linkage between sterility alleles and loci under sexually antagonistic selection significantly alters these classical predictions. We identify three specific consequences of linkage for the evolution of dimorphic sexual systems. First, linkage broadens conditions for the invasion of unisexual sterility alleles, facilitating transitions to sexual systems that are intermediate between hermaphroditism and dioecy (andro- and gynodioecy). Second, linkage elevates the equilibrium frequencies of unisexual individuals within andro- and gynodioecious populations, which promotes subsequent transitions to full dioecy. Third, linkage dampens the role of inbreeding during transitions to andro- and gynodioecy, making these transitions feasible in outbred populations. We discuss implications of these results for the evolution of dimorphic reproductive systems and sex chromosomes. </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, 06 Feb 2019 06:00:00 GMT “Predicting habitat choice after rapid environmental change” https://amnat.org/an/newpapers/MayCrowley.html The DOI will be https://dx.doi.org/10.1086/702590 Choosing where to settle is a critical decision various animals have to take, whether it is a bird choosing its nest site, or a fish larvae settling on a home coral. While we know that environmental changes are impacting many habitats and can have major fitness implications, it is harder to predict how these changes in the availability and quality of natural habitats will affect the settlement decisions of different species. A small number of species are actually thriving following environmental changes (e.g. pigeons and other urban exploiters), while many others are making poor habitat choices and consequently decline. We have developed an analytical model to predict: 1) which kinds of environmental change have large, negative effects on fitness (e.g., which is worse: lower average quality or frequency of finding patches?); 2) how species’ evolutionary histories affect their susceptibility to environmental change (are those that are used to rare habitats beforehand less affected?); and 3) how much lost fitness can be recovered via re-adjustment after environmental change (and which scenarios are non-fixable?). In our model, animals search for habitable patches in an otherwise inhospitable matrix. They are assumed to settle when they find a patch which exceeds their threshold of necessary quality. We consider decisions and fitness before environmental change, immediately following change (i.e., if the animals continue to use their existing decision thresholds), and after optimal re-adjustment (e.g., via learning or evolution). We find that decreases in survival during searching (per time step), and declines in habitat quality or availability, generally have stronger negative effects than reduced season duration. Animals that are adapted to good conditions remain choosy after conditions decline and thus suffer more from environmental change than those adapted to poor conditions beforehand. Re-adjustment can recover much of the lost fitness in some situations, such as a reduction in average habitat quality, but re-adjustment recovers much less of the lost fitness when environmental change has reduced habitat availability, or has increased death-rates during the search process. Taken together, these findings increase our ability to predict which species will be more vulnerable to environmental changes and to better prioritize conservation efforts. Abstract Decisions made while searching for settlement sites (e.g., nesting, oviposition) often have major fitness implications. Despite numerous case studies, we lack theory to explain why some species are thriving while others are making poor habitat choices after environmental change. We develop a model to predict: 1) which kinds of environmental change have larger, negative effects on fitness; 2) how evolutionary history affects susceptibility to environmental change; and 3) how much lost fitness can be recovered via re-adjustment after environmental change. We model the common scenario where animals search an otherwise inhospitable matrix, encountering habitats of varying quality, and settling when finding a habitat better than a threshold quality level. We consider decisions and fitness before environmental change, immediately following change (assuming that animals continue to use their previously adaptive decision rules), and after optimal re-adjustment (e.g., via learning or evolution). We find that decreases in survival per time step searching, and declines in habitat quality or availability, generally have stronger negative effects than reduced season duration. Animals that were adapted to good conditions remained choosy after conditions declined and thus suffered more from environmental change than those adapted to poor conditions. Re-adjustment recovered much of the fitness lost through a reduction in average habitat quality, but recovered much less following reductions in habitat availability or survival while searching. Our model offers novel predictions for empiricists to test, as well as suggestions for prioritizing alternative mitigation steps. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702590 </i></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>hoosing where to settle is a critical decision various animals have to take, whether it is a bird choosing its nest site, or a fish larvae settling on a home coral. While we know that environmental changes are impacting many habitats and can have major fitness implications, it is harder to predict how these changes in the availability and quality of natural habitats will affect the settlement decisions of different species. A small number of species are actually thriving following environmental changes (e.g. pigeons and other urban exploiters), while many others are making poor habitat choices and consequently decline. We have developed an analytical model to predict: 1) which kinds of environmental change have large, negative effects on fitness (e.g., which is worse: lower average quality or frequency of finding patches?); 2) how species’ evolutionary histories affect their susceptibility to environmental change (are those that are used to rare habitats beforehand less affected?); and 3) how much lost fitness can be recovered via re-adjustment after environmental change (and which scenarios are non-fixable?). In our model, animals search for habitable patches in an otherwise inhospitable matrix. They are assumed to settle when they find a patch which exceeds their threshold of necessary quality. We consider decisions and fitness before environmental change, immediately following change (i.e., if the animals continue to use their existing decision thresholds), and after optimal re-adjustment (e.g., via learning or evolution). We find that decreases in survival during searching (per time step), and declines in habitat quality or availability, generally have stronger negative effects than reduced season duration. Animals that are adapted to good conditions remain choosy after conditions decline and thus suffer more from environmental change than those adapted to poor conditions beforehand. Re-adjustment can recover much of the lost fitness in some situations, such as a reduction in average habitat quality, but re-adjustment recovers much less of the lost fitness when environmental change has reduced habitat availability, or has increased death-rates during the search process. Taken together, these findings increase our ability to predict which species will be more vulnerable to environmental changes and to better prioritize conservation efforts. </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;">D</span>ecisions made while searching for settlement sites (e.g., nesting, oviposition) often have major fitness implications. Despite numerous case studies, we lack theory to explain why some species are thriving while others are making poor habitat choices after environmental change. We develop a model to predict: 1) which kinds of environmental change have larger, negative effects on fitness; 2) how evolutionary history affects susceptibility to environmental change; and 3) how much lost fitness can be recovered via re-adjustment after environmental change. We model the common scenario where animals search an otherwise inhospitable matrix, encountering habitats of varying quality, and settling when finding a habitat better than a threshold quality level. We consider decisions and fitness before environmental change, immediately following change (assuming that animals continue to use their previously adaptive decision rules), and after optimal re-adjustment (e.g., via learning or evolution). We find that decreases in survival per time step searching, and declines in habitat quality or availability, generally have stronger negative effects than reduced season duration. Animals that were adapted to good conditions remained choosy after conditions declined and thus suffered more from environmental change than those adapted to poor conditions. Re-adjustment recovered much of the fitness lost through a reduction in average habitat quality, but recovered much less following reductions in habitat availability or survival while searching. Our model offers novel predictions for empiricists to test, as well as suggestions for prioritizing alternative mitigation steps. </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> Mon, 04 Feb 2019 06:00:00 GMT “Resolving the measurement uncertainty paradox in ecological management” https://amnat.org/an/newpapers/MayMemarzadeh-A.html The DOI will be https://dx.doi.org/10.1086/702704 Algorithms from robotics can help resolve a long-standing paradox in ecological management under uncertainty Abstract Ecological management and decision-making typically focus on uncertainty about the future, but surprisingly little is known about how to account for uncertainty of the present: that is, the realities of having only partial or imperfect measurements. Our primary paradigms for handling decisions under uncertainty – the precautionary principle and optimal control – have so far given contradictory results. This paradox is best illustrated in the example of fisheries management, where many ideas that guide thinking about ecological decision making were first developed. We find that simplistic optimal control approaches have repeatedly concluded that a manager should increase catch quotas when faced with greater uncertainty about the fish biomass. Current best practices take a more precautionary approach, decreasing catch quotas by a fixed amount to account for uncertainty. Using comparisons to both simulated and historical catch data, we find that neither approach is sufficient to avoid stock collapses under moderate observational uncertainty. Using partially observed Markov decision process (POMDP) methods, we demonstrate how this paradox arises from flaws in the standard theory, which contributes to over-exploitation of fisheries and increased probability of economic and ecological collapse. In contrast, we find POMDP-based management avoids such over-exploitation while also generating higher economic value. These results have significant implications for how we handle uncertainty in both fisheries and ecological management more generally. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702704 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702704">Read the Article</a></i> </p> --> <p><b>Algorithms from robotics can help resolve a long-standing paradox in ecological management under uncertainty </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>cological management and decision-making typically focus on uncertainty about the future, but surprisingly little is known about how to account for uncertainty of the present: that is, the realities of having only partial or imperfect measurements. Our primary paradigms for handling decisions under uncertainty &ndash; the precautionary principle and optimal control &ndash; have so far given contradictory results. This paradox is best illustrated in the example of fisheries management, where many ideas that guide thinking about ecological decision making were first developed. We find that simplistic optimal control approaches have repeatedly concluded that a manager should increase catch quotas when faced with greater uncertainty about the fish biomass. Current best practices take a more precautionary approach, decreasing catch quotas by a fixed amount to account for uncertainty. Using comparisons to both simulated and historical catch data, we find that neither approach is sufficient to avoid stock collapses under moderate observational uncertainty. Using partially observed Markov decision process (POMDP) methods, we demonstrate how this paradox arises from flaws in the standard theory, which contributes to over-exploitation of fisheries and increased probability of economic and ecological collapse. In contrast, we find POMDP-based management avoids such over-exploitation while also generating higher economic value. These results have significant implications for how we handle uncertainty in both fisheries and ecological management more generally. </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> Mon, 04 Feb 2019 06:00:00 GMT “Condition-dependent begging elicits increased parental investment in a wild bird population” https://amnat.org/an/newpapers/MayBowers.html The DOI will be https://dx.doi.org/10.1086/702848 Are baby birds begging or boasting? Positively condition-dependent begging ultimately enhances offspring survival Altricial young beg for food from their parents across a diverse array of taxa. Expression of this behavior consists of a combination of auditory and visual stimuli, but exactly what offspring are communicating to their parents remains controversial. The most popular hypothesis to explain the functional message encoded by offspring begging postulates that begging signals offspring ‘need’ to parents, and that parents should respond to the degree to which feeding a particular offspring will benefit that individual offspring’s fitness, and, thus, parental fitness. This hypothesis makes several assumptions that are often not satisfied in natural families, raising the possibility that begging offers alternative kinds of information to parents. Here, investigators at the University of Memphis and Illinois State University test the hypothesis that the body condition of nestlings positively affects their begging and, consequently, the parental provisioning of food, offspring growth, and long-term recruitment of offspring into the breeding population. To enhance nestling condition, they experimentally supplemented nestling diets for four days posthatching by pipetting food into their mouths, and also manipulated glucocorticoid levels to simulate the transient increase in corticosterone induced by hunger, believed to mediate begging. In the short term, begging increased with experimental increases in glucocorticoid levels, but this effect depended on nestling satiety. Thus, glucocorticoids promoted begging as an immediate manifestation of offspring hunger. However, days after the food supplementation ended (when there was no effect of glucocorticoid supplementation), previously food-supplemented nestlings were in better condition than non-experimental nestlings and begged for food at an increased rate; their parents, in turn, increased provisioning to a greater extent than parents of non-experimental young, as begging positively predicted food provisioning. Food-supplemented nestlings, therefore, attained above-average pre-fledging body mass, which predicted their recruitment as breeding adults in the local population. Thus, begging signals appear to have communicated offspring condition or quality to parents, eliciting increased parental allocation to enhance offspring survival. Abstract The coevolution of parental supply and offspring demand has long been thought to involve offspring need driving begging and parental care, leaving other hypotheses underexplored. In a population of wild birds, we tested experimentally whether begging serves as a negatively condition-dependent signal of need or a positively condition-dependent signal of quality. Across multiple years, we food-supplemented nestling house wrens shortly after hatching, and simultaneously manipulated corticosterone levels to simulate the hunger-induced increase in glucocorticoids thought to mediate begging. This allowed us also to test whether begging is simply a proximate signal of hunger. Days after supplementation ended, food-supplemented nestlings were in better condition than non-supplemented nestlings and begged for food at an increased rate; their parents, in turn, increased provisioning to a greater extent than parents of non-supplemented young, as begging positively predicted provisioning. Food-supplemented nestlings, therefore, attained above-average condition, which predicted their recruitment as breeding adults in the local population. Glucocorticoids increased begging in the short-term, but this transient effect depended on satiety. Thus, glucocorticoids promoted begging as a proximate response to hunger, whereas the longer-term changes in nestling condition, begging, and food provisioning suggest that begging ultimately signals offspring quality to elicit increased investment, thereby enhancing offspring survival. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702848 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702848">Read the Article</a></i> </p> --> <p><b>Are baby birds begging or boasting? Positively condition-dependent begging ultimately enhances offspring survival </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;">A</span>ltricial young beg for food from their parents across a diverse array of taxa. Expression of this behavior consists of a combination of auditory and visual stimuli, but exactly what offspring are communicating to their parents remains controversial. The most popular hypothesis to explain the functional message encoded by offspring begging postulates that begging signals offspring ‘need’ to parents, and that parents should respond to the degree to which feeding a particular offspring will benefit that individual offspring’s fitness, and, thus, parental fitness. This hypothesis makes several assumptions that are often not satisfied in natural families, raising the possibility that begging offers alternative kinds of information to parents. Here, investigators at the University of Memphis and Illinois State University test the hypothesis that the body condition of nestlings positively affects their begging and, consequently, the parental provisioning of food, offspring growth, and long-term recruitment of offspring into the breeding population. To enhance nestling condition, they experimentally supplemented nestling diets for four days posthatching by pipetting food into their mouths, and also manipulated glucocorticoid levels to simulate the transient increase in corticosterone induced by hunger, believed to mediate begging. In the short term, begging increased with experimental increases in glucocorticoid levels, but this effect depended on nestling satiety. Thus, glucocorticoids promoted begging as an immediate manifestation of offspring hunger. However, days after the food supplementation ended (when there was no effect of glucocorticoid supplementation), previously food-supplemented nestlings were in better condition than non-experimental nestlings and begged for food at an increased rate; their parents, in turn, increased provisioning to a greater extent than parents of non-experimental young, as begging positively predicted food provisioning. Food-supplemented nestlings, therefore, attained above-average pre-fledging body mass, which predicted their recruitment as breeding adults in the local population. Thus, begging signals appear to have communicated offspring condition or quality to parents, eliciting increased parental allocation to enhance offspring survival.</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>he coevolution of parental supply and offspring demand has long been thought to involve offspring need driving begging and parental care, leaving other hypotheses underexplored. In a population of wild birds, we tested experimentally whether begging serves as a negatively condition-dependent signal of need or a positively condition-dependent signal of quality. Across multiple years, we food-supplemented nestling house wrens shortly after hatching, and simultaneously manipulated corticosterone levels to simulate the hunger-induced increase in glucocorticoids thought to mediate begging. This allowed us also to test whether begging is simply a proximate signal of hunger. Days after supplementation ended, food-supplemented nestlings were in better condition than non-supplemented nestlings and begged for food at an increased rate; their parents, in turn, increased provisioning to a greater extent than parents of non-supplemented young, as begging positively predicted provisioning. Food-supplemented nestlings, therefore, attained above-average condition, which predicted their recruitment as breeding adults in the local population. Glucocorticoids increased begging in the short-term, but this transient effect depended on satiety. Thus, glucocorticoids promoted begging as a proximate response to hunger, whereas the longer-term changes in nestling condition, begging, and food provisioning suggest that begging ultimately signals offspring quality to elicit increased investment, thereby enhancing offspring survival. </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> Mon, 04 Feb 2019 06:00:00 GMT “Larger area facilitates richness-function effects in experimental microcosms” https://amnat.org/an/newpapers/MayDeLongGibert.html The DOI will be https://dx.doi.org/10.1086/702705 Biodiversity ecosystem function and species area curves are linked in experimental island communities Patterns of species diversity, abundance, and their ability to turn over energy and matter (or “function”) at the level of collections of species and their interactions – i.e., ecological communities – are generally viewed as separate properties that require separate explanations. This is strange because the underlying processes determining which individuals of which species conducting which ecological functions in any community must drive the aggregate properties however they are measured. For example, the increase in the number of species with an increase in the area sampled (or a species-area (SAR) curve) or the increase in ecosystem function with an increase in the number of species (or a biodiversity-ecosystem function (BEF) relationship), are central patterns in ecology and are generally treated as separate phenomena. However, the processes determining how many species occur in a place and how much they can do (eat and digest things, turn around energy and matter, etc.) must, at some level, be related. John DeLong and Jean-Philippe Gibert of the University of Nebraska–Lincoln show that these two patterns are indeed linked and together likely emerge from the same underlying processes. The authors constructed experimental microcosms (i.e., tiny constructs that simulate the conditions of freshwater ecosystems in the lab) of protists across a range of Petri dish sizes and measured species richness, abundance, functional diversity, and functioning (carbon and nitrogen content, total biovolume, and oxygen consumption). They found an increase in species richness and oxygen consumption with increasing dish area, indicating that SARs and BEF patterns occur together. Digging into the abundance and functional diversity data, the authors found that the most likely source of both patterns was diversification of niche use (e.g., food types, places to hang out, species they interact with) in the larger dishes that allowed rarer species not to go extinct as often as they do in smaller dishes. The authors also found evidence that higher nutrient turnover – possibly through the action of bacteria – may have contributed to the higher richness and function in larger dishes. Abstract Species-area (SAR) and biodiversity-ecosystem function (BEF) relationships are central patterns in community ecology. Although research on both patterns often invokes mechanisms of community assembly, both SARs and BEFs are generally treated as separate phenomenon. Here we link the two by creating an experimental SAR in microcosm communities and show that greater species richness in larger areas is accompanied by greater ecosystem function. We then explore mechanisms of community assembly by determining whether rare, large, or high biomass species are more likely to persist in the larger microcosms. Our results indicate that larger areas harbor more rare species of a wider range of body sizes and have higher functional diversity, implying that the addition of niche space that supports rare species underlies the effect of area on species richness and function. Our results suggest that the preservation of large areas is a potentially useful way of maximizing the provisioning of ecosystem services through the maintenance of biodiversity. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702705 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702705">Read the Article</a></i> </p> --> <p><b>Biodiversity ecosystem function and species area curves are linked in experimental island communities </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>atterns of species diversity, abundance, and their ability to turn over energy and matter (or “function”) at the level of collections of species and their interactions – i.e., ecological communities – are generally viewed as separate properties that require separate explanations. This is strange because the underlying processes determining which individuals of which species conducting which ecological functions in any community must drive the aggregate properties however they are measured. For example, the increase in the number of species with an increase in the area sampled (or a species-area (SAR) curve) or the increase in ecosystem function with an increase in the number of species (or a biodiversity-ecosystem function (BEF) relationship), are central patterns in ecology and are generally treated as separate phenomena. However, the processes determining how many species occur in a place and how much they can do (eat and digest things, turn around energy and matter, etc.) must, at some level, be related. John DeLong and Jean-Philippe Gibert of the University of Nebraska–Lincoln show that these two patterns are indeed linked and together likely emerge from the same underlying processes. </p><p>The authors constructed experimental microcosms (i.e., tiny constructs that simulate the conditions of freshwater ecosystems in the lab) of protists across a range of Petri dish sizes and measured species richness, abundance, functional diversity, and functioning (carbon and nitrogen content, total biovolume, and oxygen consumption). They found an increase in species richness and oxygen consumption with increasing dish area, indicating that SARs and BEF patterns occur together. Digging into the abundance and functional diversity data, the authors found that the most likely source of both patterns was diversification of niche use (e.g., food types, places to hang out, species they interact with) in the larger dishes that allowed rarer species not to go extinct as often as they do in smaller dishes. The authors also found evidence that higher nutrient turnover – possibly through the action of bacteria – may have contributed to the higher richness and function in larger dishes. </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>pecies-area (SAR) and biodiversity-ecosystem function (BEF) relationships are central patterns in community ecology. Although research on both patterns often invokes mechanisms of community assembly, both SARs and BEFs are generally treated as separate phenomenon. Here we link the two by creating an experimental SAR in microcosm communities and show that greater species richness in larger areas is accompanied by greater ecosystem function. We then explore mechanisms of community assembly by determining whether rare, large, or high biomass species are more likely to persist in the larger microcosms. Our results indicate that larger areas harbor more rare species of a wider range of body sizes and have higher functional diversity, implying that the addition of niche space that supports rare species underlies the effect of area on species richness and function. Our results suggest that the preservation of large areas is a potentially useful way of maximizing the provisioning of ecosystem services through the maintenance of biodiversity. </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> Mon, 04 Feb 2019 06:00:00 GMT “Upscaling microclimatic conditions into body temperature distributions of ectotherms” https://amnat.org/an/newpapers/MayRubalcaba.html The DOI will be https://dx.doi.org/10.1086/702717 An information-theoretical model to predict body temperature of ectotherms from microclimatic data A&nbsp;current challenge for quantitative ecologists is to forecast the organismal responses to climate change. This task requires developing models to predict, for example, how increasing ambient temperatures actually influence body temperature of individuals and their potential to adapt to novel climatic conditions. Many cold-blooded animals (such as invertebrates, frogs, or lizards) can control their body temperatures by exploiting the heterogeneity of their environment, choosing among sunny or shaded areas, basking sites or burrows. Using models to predict the response of cold-blooded animals to climate change is challenging because they require a vast amount of information to compute microhabitat preferences and physiological and behavioral features of species for which this information is often lacking. So far, there is no general model capable of dealing with uncertain information and still making accurate predictions on the actual body temperature of cold-blooded animals from climatic data. A team of researchers from Spain and Brazil has taken a step further in breaking this barrier by developing a model capable of predicting body temperature of lizards in the field. The model uses principles of information theory and statistical mechanics from physics to derive the most probable allocation scheme of individuals among the repertoire of microhabitats (e.g., sun, shade, burrows). Then, using a thermodynamic model, it computes the actual body temperature in a probabilistic way. Further, their model quantifies the importance of active control of body temperature for cold-blooded animals, for example, through avoiding exposure to sun radiation during the central hours of the day. In addition to providing a novel theoretical framework for understanding and simulating thermoregulation of cold-blooded animals, this study makes a first step towards reliable projections of organismal responses to future climates. Abstract Realistic projections of the biological impacts of climate change require predicting fitness responses to variations in environmental conditions. For ectotherms, this challenge requires methods to scale-up microclimatic information into actual body temperatures, Tb, while dealing with uncertainty regarding individual behaviors and physiological constraints. Here, we propose an information-theoretical model to derive microhabitat selection and Tb distributions of ectotherm populations from microclimatic data. The model infers the most probable allocation of individuals among the available microenvironments and the associated population-level Tb distribution. Using empirical Tb data of 41 species of desert lizards from three independently evolved systems – Western North America, Kalahari Desert, and Western Australia – we show that the model accurately predicts empirical Tb distributions across the three systems. Moreover, the framework naturally provides a way to quantify the importance of thermoregulation in a thermal environment and thereby a measurement for the constraint imposed by the climatic conditions. By predicting Tb distribution of ectotherm populations, even without exhaustive information on the underpinning mechanisms, our approach forms a solid theoretical basis for upscaling microclimatic and physiological information into a population-level fitness trait. This scaling process is a first step to reliably project the biological impacts of climate change to broad temporal and spatial scales. Escalando condiciones microclimáticas en distribuciones de temperatura corporal de ectotermos Para predecir de manera fiable los impactos bióticos del cambio climático, es necesario predecir cómo la eficacia biológica responde a variaciones en las condiciones ambientales. En ectotermos, este reto requiere de métodos que permitan escalar información microclimática a temperaturas corporales reales, Tb, y al mismo tiempo lidiar con la incertidumbre derivada de comportamientos individuales y limitantes fisiológicas. En este trabajo, proponemos un modelo basado en teoría de la información que permite calcular la preferencia de microhábitats y distribuciones de Tb de poblaciones de ectotermos a partir de datos microclimáticos. El modelo infiere la distribución espacial más probable de los individuos entre los microambientes disponibles y la distribución de Tb a nivel de población. Utilizando datos empíricos de Tb de 41 especies de lagartos de desierto provenientes de tres sistemas independientes –oeste de Norteamérica, Desierto del Kalahari y oeste de Australia– mostramos que el modelo logra predecir con precisión las distribuciones de Tb a través de los tres sistemas. Además de esto, el método permite cuantificar la importancia de la termorregulación en un ambiente térmico y con ello, aportar una medida de las restricciones térmicas impuestas por las condiciones climáticas. Al predecir la distribución de Tb de poblaciones de ectotermos, aún en ausencia de información exhaustiva de los mecanismos subyacentes, nuestro modelo aporta una base teórica sólida para estimar un rasgo relacionado con la eficacia biológica a nivel poblacional a partir de información microclimática y fisiológica. Este es un primer paso para predecir de manera fiable los impactos bióticos del cambio climático a escalas espaciales y temporales amplias. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702717 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702717">Read the Article</a></i> </p> --> <p><b>An information-theoretical model to predict body temperature of ectotherms from microclimatic data </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;">A</span>&nbsp;current challenge for quantitative ecologists is to forecast the organismal responses to climate change. This task requires developing models to predict, for example, how increasing ambient temperatures actually influence body temperature of individuals and their potential to adapt to novel climatic conditions. Many cold-blooded animals (such as invertebrates, frogs, or lizards) can control their body temperatures by exploiting the heterogeneity of their environment, choosing among sunny or shaded areas, basking sites or burrows. Using models to predict the response of cold-blooded animals to climate change is challenging because they require a vast amount of information to compute microhabitat preferences and physiological and behavioral features of species for which this information is often lacking. So far, there is no general model capable of dealing with uncertain information and still making accurate predictions on the actual body temperature of cold-blooded animals from climatic data. </p><p>A team of researchers from Spain and Brazil has taken a step further in breaking this barrier by developing a model capable of predicting body temperature of lizards in the field. The model uses principles of information theory and statistical mechanics from physics to derive the most probable allocation scheme of individuals among the repertoire of microhabitats (e.g., sun, shade, burrows). Then, using a thermodynamic model, it computes the actual body temperature in a probabilistic way. Further, their model quantifies the importance of active control of body temperature for cold-blooded animals, for example, through avoiding exposure to sun radiation during the central hours of the day. In addition to providing a novel theoretical framework for understanding and simulating thermoregulation of cold-blooded animals, this study makes a first step towards reliable projections of organismal responses to future climates. </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;">R</span>ealistic projections of the biological impacts of climate change require predicting fitness responses to variations in environmental conditions. For ectotherms, this challenge requires methods to scale-up microclimatic information into actual body temperatures, T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span>, while dealing with uncertainty regarding individual behaviors and physiological constraints. Here, we propose an information-theoretical model to derive microhabitat selection and T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> distributions of ectotherm populations from microclimatic data. The model infers the most probable allocation of individuals among the available microenvironments and the associated population-level T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> distribution. Using empirical T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> data of 41 species of desert lizards from three independently evolved systems – Western North America, Kalahari Desert, and Western Australia – we show that the model accurately predicts empirical T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> distributions across the three systems. Moreover, the framework naturally provides a way to quantify the importance of thermoregulation in a thermal environment and thereby a measurement for the constraint imposed by the climatic conditions. By predicting T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> distribution of ectotherm populations, even without exhaustive information on the underpinning mechanisms, our approach forms a solid theoretical basis for upscaling microclimatic and physiological information into a population-level fitness trait. This scaling process is a first step to reliably project the biological impacts of climate change to broad temporal and spatial scales. </p> <h4>Escalando condiciones microclimáticas en distribuciones de temperatura corporal de ectotermos</h4> <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>ara predecir de manera fiable los impactos bióticos del cambio climático, es necesario predecir cómo la eficacia biológica responde a variaciones en las condiciones ambientales. En ectotermos, este reto requiere de métodos que permitan escalar información microclimática a temperaturas corporales reales, T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span>, y al mismo tiempo lidiar con la incertidumbre derivada de comportamientos individuales y limitantes fisiológicas. En este trabajo, proponemos un modelo basado en teoría de la información que permite calcular la preferencia de microhábitats y distribuciones de T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> de poblaciones de ectotermos a partir de datos microclimáticos. El modelo infiere la distribución espacial más probable de los individuos entre los microambientes disponibles y la distribución de T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> a nivel de población. Utilizando datos empíricos de T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> de 41 especies de lagartos de desierto provenientes de tres sistemas independientes –oeste de Norteamérica, Desierto del Kalahari y oeste de Australia– mostramos que el modelo logra predecir con precisión las distribuciones de T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> a través de los tres sistemas. Además de esto, el método permite cuantificar la importancia de la termorregulación en un ambiente térmico y con ello, aportar una medida de las restricciones térmicas impuestas por las condiciones climáticas. Al predecir la distribución de T<span style="font-size:70%; position:relative; bottom:-0.3em;">b</span> de poblaciones de ectotermos, aún en ausencia de información exhaustiva de los mecanismos subyacentes, nuestro modelo aporta una base teórica sólida para estimar un rasgo relacionado con la eficacia biológica a nivel poblacional a partir de información microclimática y fisiológica. Este es un primer paso para predecir de manera fiable los impactos bióticos del cambio climático a escalas espaciales y temporales amplias. </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> Mon, 04 Feb 2019 06:00:00 GMT Best Practices Checklist for Authors and Reviewers https://amnat.org/announcements/MS-Checklist.html A number of journals have introduced checklists in recent years, aimed at either reviewers or authors. The Editorial Board of The American Naturalist is adopting a checklist as well. It is for the use of authors and reviewers and not for submission to the journal. The intent is to remind authors of items that reviewers (and readers) expect in a paper. It may also serve to remind reviewers of things they should look for, but which often get overlooked. Because we receive both a mix of theory and data and synthesis and meta-analysis papers, there is no one-size-fits-all checklist. ____________ Rationale: A paper by Parker et al (2018. “Empowering peer reviewers with a checklist to improve transparency”, Nature Ecology and Evolution) advocated greater use of checklists in evaluating research publications. They argue that “Good checklists do not replace complex thought; they facilitate it. &hellip; by calling attention to essential elements that are often overlooked”. Here, we provide a set of checklists tailored to the diverse kinds of papers submitted to The American Naturalist. Authors and reviewers are not required to use this checklist, but it may help each identify common weaknesses that need to be fixed. Not all items in the following checklist pertain to all studies. It is the job of the authors and reviewers to judge what elements apply to any given study. The checklist is therefore not meant to be a straight-jacket, but rather a prompt to remind us what authors should aspire to do, and what reviewers should check for. The checklists below do not cover methods, syntheses, historical perspectives, and some other articles that are also welcome at this journal. Authors: The checklists are designed to remind you of key features that maximize transparency of your work and that reviewers look for in evaluating your work. We encourage you to examine relevant parts of this checklist before submissionof a new manuscript, or during revision, to ensure that you are meeting our expectations. Using this checklist may help you pre-emptively avoid common reviewer critiques. Authors should also visit the journal webpage for formatting details:&nbsp;&nbsp; https://www.journals.uchicago.edu/journals/an/instruct Reviewers: You may find the checklist to be a useful reminder of manuscript features to comment on, including somewhat mundane details that authors frequently forget to include (and reviewers frequently forget to check for). Contents: 1:&nbsp;&nbsp; General considerations 2:&nbsp;&nbsp; Articles with empirical data 3:&nbsp;&nbsp; Articles with meta-analysis 4:&nbsp;&nbsp; Articles with theory 5:&nbsp;&nbsp; Submission FormattingBest-practices-checklist-edited.pdf <p>A number of journals have introduced checklists in recent years, aimed at either reviewers or authors. The Editorial Board of <em>The American Naturalist</em> is adopting a checklist as well. <strong>It is for the use of authors and reviewers and not for submission to the journal. </strong></p> <p>The intent is to remind authors of items that reviewers (and readers) expect in a paper. It may also serve to remind reviewers of things they should look for, but which often get overlooked. Because we receive both a mix of theory and data and synthesis and meta-analysis papers, there is no one-size-fits-all checklist.</p> <p>____________</p> <p><strong>Rationale:</strong></p> <p>A paper by Parker et al (2018. &ldquo;Empowering peer reviewers with a checklist to improve transparency&rdquo;, <em>Nature Ecology and Evolution</em>) advocated greater use of checklists in evaluating research publications. They argue that &ldquo;Good checklists do not replace complex thought; they facilitate it. &hellip; by calling attention to essential elements that are often overlooked&rdquo;. Here, we provide a set of checklists tailored to the diverse kinds of papers submitted to <em>The American Naturalist.</em> Authors and reviewers are not required to use this checklist, but it may help each identify common weaknesses that need to be fixed. Not all items in the following checklist pertain to all studies. It is the job of the authors and reviewers to judge what elements apply to any given study. The checklist is therefore not meant to be a straight-jacket, but rather a prompt to remind us what authors should aspire to do, and what reviewers should check for. The checklists below do not cover methods, syntheses, historical perspectives, and some other articles that are also welcome at this journal.</p> <p><strong>Authors:</strong></p> <p>The checklists are designed to remind you of key features that maximize transparency of your work and that reviewers look for in evaluating your work. We encourage you to examine relevant parts of this checklist before submissionof a new manuscript, or during revision, to ensure that you are meeting our expectations. Using this checklist may help you pre-emptively avoid common reviewer critiques. Authors should also visit the journal webpage for formatting details:&nbsp;&nbsp; <a href="https://www.journals.uchicago.edu/journals/an/instruct">https://www.journals.uchicago.edu/journals/an/instruct</a></p> <p><strong>Reviewers</strong>:</p> <p>You may find the checklist to be a useful reminder of manuscript features to comment on, including somewhat mundane details that authors frequently forget to include (and reviewers frequently forget to check for).</p> <p>Contents:<br /> 1:&nbsp;&nbsp; General considerations<br /> 2:&nbsp;&nbsp; Articles with empirical data<br /> 3:&nbsp;&nbsp; Articles with meta-analysis<br /> 4:&nbsp;&nbsp; Articles with theory<br /> 5:&nbsp;&nbsp; Submission Formatting</p><p><a href="/dam/jcr:3cbc3ea2-1109-495e-9b7d-04cec4fc18d1/Best%20practices%20checklist%20edited.pdf">Best-practices-checklist-edited.pdf</a></p> Mon, 04 Feb 2019 06:00:00 GMT “Heterogeneous matrix habitat drives species occurrences in complex, fragmented landscapes” https://amnat.org/an/newpapers/MayBrodie-A.html The DOI will be https://dx.doi.org/10.1086/702589 Abstract A&nbsp;fundamental tenet of modern ecology and conservation science is that species occurrence in habitat patches can be determined by patch area and isolation. But such island biogeographic models often poorly predict actual species occurrences in structurally complex landscapes that typify most ecosystems. Recent advances in circuit theory have enhanced estimates of species dispersal, and through integration with island biogeography, can provide powerful ways to predict landscape-scale distribution of species assemblages. Applying such an integrative analytical framework to 43 bird species in Tanzania improved model fit by an average of 2.2-fold over models where patch isolation was estimated without accounting for landscape matrix heterogeneity. This approach also allowed us to assess species-specific dispersal rates and quantify differences among land cover types in their permeability to animal movement. These results reaffirm the utility of foundational island biogeographic principles, yet with an important caveat. Two-thirds of the variance in species occurrence in habitat fragments can be explained simply by patch area and isolation, conditional on isolation explicitly accounting for the spatial configuration of different land cover types in the landscape matrix. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702589 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702589">Read the Article</a></i> </p> --><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;">A</span>&nbsp;fundamental tenet of modern ecology and conservation science is that species occurrence in habitat patches can be determined by patch area and isolation. But such island biogeographic models often poorly predict actual species occurrences in structurally complex landscapes that typify most ecosystems. Recent advances in circuit theory have enhanced estimates of species dispersal, and through integration with island biogeography, can provide powerful ways to predict landscape-scale distribution of species assemblages. Applying such an integrative analytical framework to 43 bird species in Tanzania improved model fit by an average of 2.2-fold over models where patch isolation was estimated without accounting for landscape matrix heterogeneity. This approach also allowed us to assess species-specific dispersal rates and quantify differences among land cover types in their permeability to animal movement. These results reaffirm the utility of foundational island biogeographic principles, yet with an important caveat. Two-thirds of the variance in species occurrence in habitat fragments can be explained simply by patch area and isolation, conditional on isolation explicitly accounting for the spatial configuration of different land cover types in the landscape matrix.</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> Wed, 16 Jan 2019 06:00:00 GMT “Prey responses to exotic predators: effects of old risks and new cues” https://amnat.org/an/newpapers/AprEhlman.html The DOI will be https://dx.doi.org/10.1086/702252 New theory on prey responses to exotic predators offers insights and surprises Behavioral ecological theory on the interactions of predators and prey commonly assumes that predators and prey have coevolved to respond appropriately to one another. Increasingly in the modern world, however, prey must face exotic, invasive predators to which they are not well-adapted. This work develops a predictive, cue-based theory of prey responses to exotic predators. The authors ask how differences in preys’ evolutionary histories with native predators might explain variation in their success with exotic predators: Does the degree of similarity between native and non-native predator cues affect prey responses? Usually. Does the frequency of predation in a prey’s past affect responses to exotic predators? A bit, but sometimes in the opposite direction of previous work. Does the degree to which prey generalize among predator types affect their perception of risk with exotic predators? Yes, in some interesting ways. For empiricists working towards understanding variation in prey responses to exotic predators, this theory offers insights and testable predictions. Abstract Exotic predators can have major negative impacts on prey. Importantly, prey vary considerably in their behavioral responses to exotic predators. Factors proposed to explain variation in prey response to exotic predators include the similarity of new predators to familiar, native predators, the prevalence and diversity of predators in a prey’s past, and variation in a prey’s innate ability to discriminate between predators and safety. While these factors have been put forth verbally in the literature, no theory exists that combines these hypotheses in a common conceptual framework using a unified behavioral model. Here, we formalize existing verbal arguments by modeling variation in prey responses to new predators in a state-dependent detection theory (SDDT) framework. We find that while some conventional wisdom is upheld, novel predictions emerge. As expected, prey respond poorly to exotic predators that do not closely resemble familiar predators. Furthermore, a history with more abundant or diverse native predators can lessen effects of some exotic predators on prey; however, under some conditions, the opposite prediction emerges. Also, prey that evolved in situations where they easily discriminate between safe and dangerous situations can be more susceptible to novel predators. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702252 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702252">Read the Article</a></i> </p> --> <p><b>New theory on prey responses to exotic predators offers insights and surprises </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;">B</span>ehavioral ecological theory on the interactions of predators and prey commonly assumes that predators and prey have coevolved to respond appropriately to one another. Increasingly in the modern world, however, prey must face exotic, invasive predators to which they are not well-adapted. This work develops a predictive, cue-based theory of prey responses to exotic predators. The authors ask how differences in preys’ evolutionary histories with native predators might explain variation in their success with exotic predators: Does the degree of similarity between native and non-native predator cues affect prey responses? Usually. Does the frequency of predation in a prey’s past affect responses to exotic predators? A bit, but sometimes in the opposite direction of previous work. Does the degree to which prey generalize among predator types affect their perception of risk with exotic predators? Yes, in some interesting ways. For empiricists working towards understanding variation in prey responses to exotic predators, this theory offers insights and testable predictions. </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>xotic predators can have major negative impacts on prey. Importantly, prey vary considerably in their behavioral responses to exotic predators. Factors proposed to explain variation in prey response to exotic predators include the similarity of new predators to familiar, native predators, the prevalence and diversity of predators in a prey’s past, and variation in a prey’s innate ability to discriminate between predators and safety. While these factors have been put forth verbally in the literature, no theory exists that combines these hypotheses in a common conceptual framework using a unified behavioral model. Here, we formalize existing verbal arguments by modeling variation in prey responses to new predators in a state-dependent detection theory (SDDT) framework. We find that while some conventional wisdom is upheld, novel predictions emerge. As expected, prey respond poorly to exotic predators that do not closely resemble familiar predators. Furthermore, a history with more abundant or diverse native predators can lessen effects of some exotic predators on prey; however, under some conditions, the opposite prediction emerges. Also, prey that evolved in situations where they easily discriminate between safe and dangerous situations can be more susceptible to novel predators. </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 Jan 2019 06:00:00 GMT “Evolution of the two sexes under internal fertilization and alternative evolutionary pathways” https://amnat.org/an/newpapers/MayLehtonen.html The DOI will be https://dx.doi.org/10.1086/702588 Anisogamy theory is robust under internal fertilization and sperm packets, bridging gap between theory and empirical tests Biologically, the two sexes are defined by the size of their gametes. Females are by definition the type that produces the larger gametes (e.g. eggs) and males the type that produces the smaller gametes (e.g. sperm). In this sense the origin of gamete size dimorphism is synonymous with the origin of the two sexes. Our understanding of this major event in evolutionary history is largely based on so-called gamete dynamics theory, where there are simultaneous selective pressures driving selection for numerous (hence small) and large (hence less numerous) gametes. Small and numerous gametes are good at gaining fertilizations, while large gametes are good at provisioning offspring. Although empirical evidence is fairly supportive of this theory, much of the evidence comes from organisms with simple forms of internal fertilization, while the original theory is derived for external fertilizers. Furthermore, some of these organisms divide their gametes into ‘sperm packets’, further increasing the divide between theory and data. In a new article, Jussi Lehtonen of the University of Sydney, Australia, and Geoff Parker of the University of Liverpool, UK, generalize previous theory on the origin of the two sexes, showing that the theory works equally well under the biology of these model organisms. Hence gamete dynamics theory represents a potent rationale for the origin of the two sexes. Abstract Transition from isogamy to anisogamy, hence males and females, leads to sexual selection, sexual conflict, sexual dimorphism, and sex roles. Gamete dynamics theory links biophysics of gamete limitation, gamete competition and resource requirements for zygote survival, and assumes broadcast spawning. It makes testable predictions, but most comparative tests use volvocine algae, which feature internal fertilization. We broaden this theory by comparing broadcast spawning predictions with two plausible internal fertilization scenarios: gamete-casting/brooding (one mating type retains gametes internally, the other broadcasts them) and packet-casting/brooding (one type retains gametes internally, the other broadcasts packets containing gametes, which are released for fertilization). Models show that predictions are remarkably robust to these radical changes, yielding (i) isogamy under low gamete limitation, low gamete competition, and similar required resources for gametes and zygotes, (ii) anisogamy when gamete competition and/or limitation are higher, and when zygotes require more resources than gametes, as is likely as multicellularity develops, (iii) a positive correlation between multicellular complexity and anisogamy ratio, and (iv) under gamete competition, only brooders becoming female. Thus gamete dynamics theory represents a potent rationale for isogamy/anisogamy, and makes similar testable predictions for broadcast spawners and internal fertilizers, regardless of whether anisogamy or internal fertilization evolved first. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702588 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702588">Read the Article</a></i> </p> --> <p><b>Anisogamy theory is robust under internal fertilization and sperm packets, bridging gap between theory and empirical tests </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;">B</span>iologically, the two sexes are defined by the size of their gametes. Females are by definition the type that produces the larger gametes (e.g. eggs) and males the type that produces the smaller gametes (e.g. sperm). In this sense the origin of gamete size dimorphism is synonymous with the origin of the two sexes. Our understanding of this major event in evolutionary history is largely based on so-called gamete dynamics theory, where there are simultaneous selective pressures driving selection for numerous (hence small) and large (hence less numerous) gametes. Small and numerous gametes are good at gaining fertilizations, while large gametes are good at provisioning offspring. Although empirical evidence is fairly supportive of this theory, much of the evidence comes from organisms with simple forms of internal fertilization, while the original theory is derived for external fertilizers. Furthermore, some of these organisms divide their gametes into ‘sperm packets’, further increasing the divide between theory and data. In a new article, Jussi Lehtonen of the University of Sydney, Australia, and Geoff Parker of the University of Liverpool, UK, generalize previous theory on the origin of the two sexes, showing that the theory works equally well under the biology of these model organisms. Hence gamete dynamics theory represents a potent rationale for the origin of the two sexes. </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>ransition from isogamy to anisogamy, hence males and females, leads to sexual selection, sexual conflict, sexual dimorphism, and sex roles. Gamete dynamics theory links biophysics of gamete limitation, gamete competition and resource requirements for zygote survival, and assumes broadcast spawning. It makes testable predictions, but most comparative tests use volvocine algae, which feature internal fertilization. We broaden this theory by comparing broadcast spawning predictions with two plausible internal fertilization scenarios: gamete-casting/brooding (one mating type retains gametes internally, the other broadcasts them) and packet-casting/brooding (one type retains gametes internally, the other broadcasts packets containing gametes, which are released for fertilization). Models show that predictions are remarkably robust to these radical changes, yielding (i) isogamy under low gamete limitation, low gamete competition, and similar required resources for gametes and zygotes, (ii) anisogamy when gamete competition and/or limitation are higher, and when zygotes require more resources than gametes, as is likely as multicellularity develops, (iii) a positive correlation between multicellular complexity and anisogamy ratio, and (iv) under gamete competition, only brooders becoming female. Thus gamete dynamics theory represents a potent rationale for isogamy/anisogamy, and makes similar testable predictions for broadcast spawners and internal fertilizers, regardless of whether anisogamy or internal fertilization evolved first.</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 Jan 2019 06:00:00 GMT “Nighttime ecology: the ‘nocturnal problem’ revisited” https://amnat.org/an/newpapers/AprGaston-A.html The DOI will be https://dx.doi.org/10.1086/702250 Abstract The existence of a synthetic program of research on what was then termed ‘the nocturnal problem’, and which we might now call ‘nighttime ecology’, was declared more than 70 years ago. In reality this failed to materialize, arguably as a consequence of practical challenges in studying organisms at night and concentration instead on the existence of circadian rhythms, the mechanisms that give rise to them, and their consequences. This legacy is evident to this day, with consideration of the ecology of the nighttime markedly underrepresented in ecological research and literature. However, several factors suggest that it would be timely to revive the vision of a comprehensive research program in nighttime ecology. These include (i) that study of the ecology of the night is being revolutionized by new and improved technologies,; (ii) suggestions that far from being a minor component of biodiversity a high proportion of animal species are active at night; (iii) that fundamental questions remain largely unanswered as to differences and connections between the ecology of the daytime and nighttime; and (iv) that the nighttime environment is coming under severe anthropogenic pressure. In this article, I seek to re-establish ‘nighttime ecology’ as a synthetic program of research, highlighting key focal topics, key questions, and providing an overview of the current state of understanding and developments. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702250 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702250">Read the Article</a></i> </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 existence of a synthetic program of research on what was then termed ‘the nocturnal problem’, and which we might now call ‘nighttime ecology’, was declared more than 70 years ago. In reality this failed to materialize, arguably as a consequence of practical challenges in studying organisms at night and concentration instead on the existence of circadian rhythms, the mechanisms that give rise to them, and their consequences. This legacy is evident to this day, with consideration of the ecology of the nighttime markedly underrepresented in ecological research and literature. However, several factors suggest that it would be timely to revive the vision of a comprehensive research program in nighttime ecology. These include (i) that study of the ecology of the night is being revolutionized by new and improved technologies,; (ii) suggestions that far from being a minor component of biodiversity a high proportion of animal species are active at night; (iii) that fundamental questions remain largely unanswered as to differences and connections between the ecology of the daytime and nighttime; and (iv) that the nighttime environment is coming under severe anthropogenic pressure. In this article, I seek to re-establish ‘nighttime ecology’ as a synthetic program of research, highlighting key focal topics, key questions, and providing an overview of the current state of understanding and developments. </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 Jan 2019 06:00:00 GMT “Mate choice vs. mate preference: inferences about color assortative mating differ between field and lab assays of poison frog behavior” https://amnat.org/an/newpapers/AprYang-A.html Read the Article Choice vs. preference: patterns of color assortative mating differ between field and lab assays of poison frog behavior Abstract Co-divergence of mating traits and mate preferences can lead to behavioral isolation among lineages in early stages of speciation. However, mate preferences only limit gene flow when expressed as mate choice, and numerous factors might be more important than preferences in nature. In the extremely color polytypic strawberry poison frog (Oophaga pumilio), female mate preferences have co-diverged with color in most allopatric populations tested. Whether these lab-assayed preferences predict mating (gene flow) in the wild remains unclear. We observed courting pairs in a natural contact zone between red and blue lineages until oviposition or courtship termination. We found color-assortative mating in a disturbed habitat with high population density, but not in a secondary forest with lower density. Our results suggest color-assortative O.&nbsp;pumilio mate choice in the wild, but also mating patterns that do not match those predicted by lab-assayed preferences. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/702249"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702249">Read the Article</a></i> </p> --> <p><b>Choice vs. preference: patterns of color assortative mating differ between field and lab assays of poison frog behavior </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;">C</span>o-divergence of mating traits and mate preferences can lead to behavioral isolation among lineages in early stages of speciation. However, mate preferences only limit gene flow when expressed as mate choice, and numerous factors might be more important than preferences in nature. In the extremely color polytypic strawberry poison frog (<i>Oophaga pumilio</i>), female mate preferences have co-diverged with color in most allopatric populations tested. Whether these lab-assayed preferences predict mating (gene flow) in the wild remains unclear. We observed courting pairs in a natural contact zone between red and blue lineages until oviposition or courtship termination. We found color-assortative mating in a disturbed habitat with high population density, but not in a secondary forest with lower density. Our results suggest color-assortative <i>O.&nbsp;pumilio</i> mate choice in the wild, but also mating patterns that do not match those predicted by lab-assayed preferences. </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 Jan 2019 06:00:00 GMT “Age-specific offspring mortality economically tracks food abundance in a piscivorous seabird” https://amnat.org/an/newpapers/AprVedder.html Read the Article Earlier chick mortality with low food availability reduces the energy wasted on non-fledged chicks in poor years Why does mortality peak at the start of life? One idea is that this early mortality reduces the amount of resources wasted on unsuccessful offspring, and is the result of a strategy adopted by the parents that is beneficial when unpredictable foraging conditions turn out bad. By analysing a 24-year dataset of age-specific chick mortality of common terns (fish-eating seabirds), an international team of researchers has found that with reduced food availability, fledgling success decreased in an economical fashion. When herring (the terns’ main food source) were rare, chick mortality increased, but because chicks died earlier, this did not lead to a proportional increase in energy wasted on non-fledged chicks. Disadvantaged, last-hatching, chicks were particularly cheap when they died, but, per hatchling, the chicks without siblings required the least waste of energy. The researchers suggest that parents may facilitate early mortality of excess offspring by promoting competitive asymmetries among offspring from the start, but that competition between siblings may interfere with the parents’ best interests despite such asymmetries. These results thereby support evolutionary theory on age-specific mortality, parental effects, sibling competition, and parent-offspring-conflict. The researchers conclude, “Despite it being an extremely sad sight to see so many small chicks die when there is little food, this may be nature’s way of ensuring that the parents survive and are able to reproduce in future years when food may be more abundant.” Abstract Earlier offspring mortality prior to independence saves resources for kin, which should be more beneficial when food is short. Using 24 years of data on age-specific common tern (Sterna hirundo) chick mortality, best described by the Gompertz function, and estimates of energy consumption per age of mortality, we investigated how energy wasted on non-fledged chicks depends on brood size, hatching order and annual abundance of herring (Clupea harengus), the main food source. We found mortality directly after hatching (Gompertz baseline mortality) to be high and to increase with decreasing herring abundance. Mortality declined with age, at a rate relatively insensitive to herring abundance. The sensitivity of baseline mortality to herring abundance reduced energy wasted on non-fledged chicks when herring was short. Among chicks that did not fledge, last-hatched chicks were less costly than earlier hatched chicks, due to their earlier mortality. However, per hatchling produced, the least energy was wasted on chicks without siblings, due to their baseline mortality being most sensitive to herring abundance. We suggest that earlier mortality of offspring when food is short facilitates economic adjustment of post-hatching parental investment to food abundance, but that such economic brood reduction may be constrained by sibling competition. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/702304"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702304">Read the Article</a></i> </p> --> <p><b>Earlier chick mortality with low food availability reduces the energy wasted on non-fledged chicks in poor years </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>hy does mortality peak at the start of life? One idea is that this early mortality reduces the amount of resources wasted on unsuccessful offspring, and is the result of a strategy adopted by the parents that is beneficial when unpredictable foraging conditions turn out bad. By analysing a 24-year dataset of age-specific chick mortality of common terns (fish-eating seabirds), an international team of researchers has found that with reduced food availability, fledgling success decreased in an economical fashion. When herring (the terns’ main food source) were rare, chick mortality increased, but because chicks died earlier, this did not lead to a proportional increase in energy wasted on non-fledged chicks. Disadvantaged, last-hatching, chicks were particularly cheap when they died, but, per hatchling, the chicks without siblings required the least waste of energy. The researchers suggest that parents may facilitate early mortality of excess offspring by promoting competitive asymmetries among offspring from the start, but that competition between siblings may interfere with the parents’ best interests despite such asymmetries. These results thereby support evolutionary theory on age-specific mortality, parental effects, sibling competition, and parent-offspring-conflict. The researchers conclude, “Despite it being an extremely sad sight to see so many small chicks die when there is little food, this may be nature’s way of ensuring that the parents survive and are able to reproduce in future years when food may be more abundant.”</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>arlier offspring mortality prior to independence saves resources for kin, which should be more beneficial when food is short. Using 24 years of data on age-specific common tern (<i>Sterna hirundo</i>) chick mortality, best described by the Gompertz function, and estimates of energy consumption per age of mortality, we investigated how energy wasted on non-fledged chicks depends on brood size, hatching order and annual abundance of herring (<i>Clupea harengus</i>), the main food source. We found mortality directly after hatching (Gompertz baseline mortality) to be high and to increase with decreasing herring abundance. Mortality declined with age, at a rate relatively insensitive to herring abundance. The sensitivity of baseline mortality to herring abundance reduced energy wasted on non-fledged chicks when herring was short. Among chicks that did not fledge, last-hatched chicks were less costly than earlier hatched chicks, due to their earlier mortality. However, per hatchling produced, the least energy was wasted on chicks without siblings, due to their baseline mortality being most sensitive to herring abundance. We suggest that earlier mortality of offspring when food is short facilitates economic adjustment of post-hatching parental investment to food abundance, but that such economic brood reduction may be constrained by sibling competition. </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 Jan 2019 06:00:00 GMT “A vector-based approach to measure nutritional trade-offs within and between species” https://amnat.org/an/newpapers/JuneMorimoto.html The DOI will be https://dx.doi.org/10.1086/701898 A generalized approach to compare fitness landscapes within and between species in multi-dimensional data In Ancient Greece, somewhere around the year 300 BC, Euclid published his book Elements containing a single framework based on rigorous mathematical proof for Geometry. Little could he predict the far-reaching implications of his work. Some 22 centuries later, his life’s legacy was used to inspire biologists into creating a new framework – known as ‘nutritional geometry’, which is now widely used to investigate how animals and humans (should) eat. But how can one tell a good diet from a bad diet? And is there a universal ‘good diet recipe’ that solve all our problems? To answer these questions, scientists need to measure the effects of different diets on morphological and physiological traits, and quantify how these diets affect these traits in relation to others in the same individual, species, or between species. To date, however, there were no quantitative framework that allowed intra- and inter-specific comparisons of these effects. Building on previous attempts from colleagues, Morimoto and Lihoreau came up with a solution for this conundrum. They used the mathematical concept of vectors to quantify how much of each nutrient in the diet animals should eat to maximize a trait. Then, using fancy statistics that includes machine learning, they developed a model that could quantify differences in nutrient intake required to maximize traits within and across species. This work provides a significant advance in how we tell good from bad diets. The method of Morimoto and Lihoreau has the potential to be broadly used in ecology and evolution to understand the fundamentals of animal nutrition, but also their far-reaching consequences such as how individuals interact within societies, how species coexist and co-evolve in communities. The work can also be used in conservation and medical research to gain insights into what a healthy diet means for a given species (including us humans), and how to achieve it. Many centuries later, Euclid’s fundamental mathematical legacy becomes an evidence to explain the evolution of species, the onset of diseases, and possibly, the secret for a healthy life. Abstract Animals make feeding decisions to simultaneously maximize fitness traits that often require different nutrients. Recent quantitative methods have been developed to characterize these nutritional trade-offs from performance landscapes on which traits are mapped on a nutrient space defined by two nutrients. This limitation constrains the broad applications of previous methods to more complex data, and a generalized framework is needed. Here, we build upon previous methods and introduce a generalized vector-based approach – the Vector of Position approach – to study nutritional trade-offs in complex multi-dimensional spaces. The Vector of Position Approach allows the estimate of performance variations across entire landscapes (peaks and valleys), and comparison of these variations between animals. Using landmark published datasets on lifespan and reproduction landscapes, we illustrate how our approach gives accurate quantifications of nutritional trade-offs in two- and three-dimensional spaces, and can bring new insights into the underlying nutritional differences in trait expression between species. The Vector of Position Approach provides a generalized framework for investigating nutritional differences in life-history traits expression within and between species, an essential step for the development of comparative research on the evolution of animal nutritional strategies. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701898 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701898">Read the Article</a></i> </p> --> <p><b>A generalized approach to compare fitness landscapes within and between species in multi-dimensional data </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>n Ancient Greece, somewhere around the year 300 BC, Euclid published his book Elements containing a single framework based on rigorous mathematical proof for Geometry. Little could he predict the far-reaching implications of his work. Some 22 centuries later, his life’s legacy was used to inspire biologists into creating a new framework – known as ‘nutritional geometry’, which is now widely used to investigate how animals and humans (should) eat. But how can one tell a good diet from a bad diet? And is there a universal ‘good diet recipe’ that solve all our problems? </p><p>To answer these questions, scientists need to measure the effects of different diets on morphological and physiological traits, and quantify how these diets affect these traits in relation to others in the same individual, species, or between species. To date, however, there were no quantitative framework that allowed intra- and inter-specific comparisons of these effects. </p><p>Building on previous attempts from colleagues, Morimoto and Lihoreau came up with a solution for this conundrum. They used the mathematical concept of vectors to quantify how much of each nutrient in the diet animals should eat to maximize a trait. Then, using fancy statistics that includes machine learning, they developed a model that could quantify differences in nutrient intake required to maximize traits within and across species. </p><p>This work provides a significant advance in how we tell good from bad diets. The method of Morimoto and Lihoreau has the potential to be broadly used in ecology and evolution to understand the fundamentals of animal nutrition, but also their far-reaching consequences such as how individuals interact within societies, how species coexist and co-evolve in communities. The work can also be used in conservation and medical research to gain insights into what a healthy diet means for a given species (including us humans), and how to achieve it. Many centuries later, Euclid’s fundamental mathematical legacy becomes an evidence to explain the evolution of species, the onset of diseases, and possibly, the secret for a healthy life. </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;">A</span>nimals make feeding decisions to simultaneously maximize fitness traits that often require different nutrients. Recent quantitative methods have been developed to characterize these nutritional trade-offs from performance landscapes on which traits are mapped on a nutrient space defined by two nutrients. This limitation constrains the broad applications of previous methods to more complex data, and a generalized framework is needed. Here, we build upon previous methods and introduce a generalized vector-based approach – the Vector of Position approach – to study nutritional trade-offs in complex multi-dimensional spaces. The Vector of Position Approach allows the estimate of performance variations across entire landscapes (peaks and valleys), and comparison of these variations between animals. Using landmark published datasets on lifespan and reproduction landscapes, we illustrate how our approach gives accurate quantifications of nutritional trade-offs in two- and three-dimensional spaces, and can bring new insights into the underlying nutritional differences in trait expression between species. The Vector of Position Approach provides a generalized framework for investigating nutritional differences in life-history traits expression within and between species, an essential step for the development of comparative research on the evolution of animal nutritional strategies. </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> Fri, 11 Jan 2019 06:00:00 GMT