ASN RSS http://amnat.org/ Latest press releases and announcements from the ASN en-us Thu, 19 Jan 2017 06:00:00 GMT 60 “Mimicry among unequally defended prey should be mutualistic when predators sample optimally” http://amnat.org/an/newpapers/MarAubier.html Controversial quasi-Batesian mimicry among unequally defended prey should be rare if predators sample optimally Open almost any textbook on evolutionary biology and you will read about two forms of mimicry that students and professors continue to confuse. Batesian mimics are sheep in wolves clothing: palatable species that have evolved a resemblance to an unpalatable or otherwise defended species (the “model”) to gain protection from predators. By contrast, Müllerian mimics are wolves in wolves clothing: unpalatable species that have evolved a resemblance to other unpalatable species (“co-models”) to reduce the cost of educating naïve predators to avoid them. Batesian mimics are widely regarded as parasites, eroding the effectiveness of their model’s signals. Indeed, this parasitism can undermine the deterrent effect of the model’s appearance to such an extent that the mimic species sometimes evolve multiple morphs, with each morph resembling a different model. By contrast, Müllerian mimics are as mutualistic and reinforcing – the more unpalatable species with a given appearance, the more effective the signal. Unfortunately however, life is not quite as simple as textbooks imply. In particular, species show wide variation in their level of defenses, so when a moderately unpalatable species resembles a highly unpalatable species, is it a “quasi-Batesian” mimic, eroding the effectiveness of the shared signal, or is it a classical Müllerian mimic? This question has been hotly debated for over a century, because it has long been recognized that Batesian and Müllerian mimicry may be on something of a continuum. Its answer is important because if moderately defended prey were parasites then it could help explain the puzzling cases of polymorphism observed in unpalatable species, such as that seen in Heliconius numata (left). In this paper Thomas Aubier and his colleagues tackled the question head on, by identifying from first principles what a naïve predator should do if it encountered models and mimics with these characteristics and the predator acted in a way that maximized its payoff. After all, you would expect natural selection to come up with good solutions. Despite a great deal of analysis, their answer was relatively clear-cut. The more individuals of a given appearance there are, the more optimally sampling predators will be motivated to find out their properties. However, attacking a weakly defended mimic still represents a vote in favor of avoiding the prey type in the future. The net result is that moderately defended mimics should act as mutualists, decreasing the overall mortality of prey with this appearance, rather than parasites. While this means that researchers will have to look elsewhere to explain the puzzling examples of polymorphism in unpalatable species, it suggests that mimicry among prey with unequal defenses is generally mutualistic. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Controversial quasi-Batesian mimicry among unequally defended prey should be rare if predators sample optimally </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;">O</span>pen almost any textbook on evolutionary biology and you will read about two forms of mimicry that students and professors continue to confuse. Batesian mimics are sheep in wolves clothing: palatable species that have evolved a resemblance to an unpalatable or otherwise defended species (the “model”) to gain protection from predators. By contrast, Müllerian mimics are wolves in wolves clothing: unpalatable species that have evolved a resemblance to other unpalatable species (“co-models”) to reduce the cost of educating naïve predators to avoid them. Batesian mimics are widely regarded as parasites, eroding the effectiveness of their model’s signals. Indeed, this parasitism can undermine the deterrent effect of the model’s appearance to such an extent that the mimic species sometimes evolve multiple morphs, with each morph resembling a different model. By contrast, Müllerian mimics are as mutualistic and reinforcing – the more unpalatable species with a given appearance, the more effective the signal. </p> <p>Unfortunately however, life is not quite as simple as textbooks imply. In particular, species show wide variation in their level of defenses, so when a moderately unpalatable species resembles a highly unpalatable species, is it a “quasi-Batesian” mimic, eroding the effectiveness of the shared signal, or is it a classical Müllerian mimic? This question has been hotly debated for over a century, because it has long been recognized that Batesian and Müllerian mimicry may be on something of a continuum. Its answer is important because if moderately defended prey were parasites then it could help explain the puzzling cases of polymorphism observed in unpalatable species, such as that seen in <i>Heliconius numata</i> (<i>left</i>). </p><p> In this paper Thomas Aubier and his colleagues tackled the question head on, by identifying from first principles what a naïve predator should do if it encountered models and mimics with these characteristics and the predator acted in a way that maximized its payoff. After all, you would expect natural selection to come up with good solutions. Despite a great deal of analysis, their answer was relatively clear-cut. The more individuals of a given appearance there are, the more optimally sampling predators will be motivated to find out their properties. However, attacking a weakly defended mimic still represents a vote in favor of avoiding the prey type in the future. The net result is that moderately defended mimics should act as mutualists, decreasing the overall mortality of prey with this appearance, rather than parasites. While this means that researchers will have to look elsewhere to explain the puzzling examples of polymorphism in unpalatable species, it suggests that mimicry among prey with unequal defenses is generally mutualistic. <a href="http://dx.doi.org/10.1086/690121">Read&nbsp;the&nbsp;Article</a> </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, 19 Jan 2017 06:00:00 GMT “The behavioral type of a top predator drives the short-term dynamic of intraguild predation” http://amnat.org/an/newpapers/MarMichalko.html The behavioral types and abundances of interacting species can interactively determine the food-web dynamics Arthropod predators, like humans, show individual variation in behavior. For example, some individuals are choosy and pick up only certain prey, while others catch whatever they can overcome. Individual predators can also differ in their foraging aggressiveness, for instance killing more or fewer prey during a foraging bout. Consequently, the behavioral differences among individual predators (i.e. behavioral types) can shape the dynamic of interactions with pests and other predators occurring in an agroecosystem. Radek Michalko and Stano Pekár, researchers from Mendel and Masaryk Universities in Brno, Czech Republic, tried to disentangle the complex interactions among predators and pests in a pear orchard in order to reveal how the behavioral type of the predator can be used to improve pest control by natural enemies. They investigated the behavioral differences of the top predator and their effect on foraging efficiency against other predators and psylla pests. And then they used simulations of a mathematical model to predict the dynamic of interactions in the system during the winter and spring. They find that the timid individuals kill fewer pests and are choosy as they prefer pests to other predators. In contrast, the aggressive individuals kill more pests and do not prefer pests to other predators. Consequently, the agroecosystem with aggressive predatory individuals is generally more effective in pest control when other predators are less abundant, while the agroecosystem with timid predatory individuals is more effective when other predators are more abundant. The authors suggest that the aggressive / non-choosy predators might be useful for biocontrol in annual agroecosystems (e.g., fields of grain), while the timid / choosy predators might rather be useful in perennial agroecosystems (e.g., orchards). Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>The behavioral types and abundances of interacting species can interactively determine the food-web dynamics </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>rthropod predators, like humans, show individual variation in behavior. For example, some individuals are choosy and pick up only certain prey, while others catch whatever they can overcome. Individual predators can also differ in their foraging aggressiveness, for instance killing more or fewer prey during a foraging bout. Consequently, the behavioral differences among individual predators (i.e. behavioral types) can shape the dynamic of interactions with pests and other predators occurring in an agroecosystem. </p> <p>Radek Michalko and Stano Pekár, researchers from Mendel and Masaryk Universities in Brno, Czech Republic, tried to disentangle the complex interactions among predators and pests in a pear orchard in order to reveal how the behavioral type of the predator can be used to improve pest control by natural enemies. They investigated the behavioral differences of the top predator and their effect on foraging efficiency against other predators and psylla pests. And then they used simulations of a mathematical model to predict the dynamic of interactions in the system during the winter and spring. </p> <p>They find that the timid individuals kill fewer pests and are choosy as they prefer pests to other predators. In contrast, the aggressive individuals kill more pests and do not prefer pests to other predators. Consequently, the agroecosystem with aggressive predatory individuals is generally more effective in pest control when other predators are less abundant, while the agroecosystem with timid predatory individuals is more effective when other predators are more abundant. The authors suggest that the aggressive / non-choosy predators might be useful for biocontrol in annual agroecosystems (e.g., fields of grain), while the timid / choosy predators might rather be useful in perennial agroecosystems (e.g., orchards). <a href="http://dx.doi.org/10.1086/690501">Read&nbsp;the&nbsp;Article</a> </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, 19 Jan 2017 06:00:00 GMT “Does co-history constrain information use? Evidence for generalized risk assessment in non-native prey” http://amnat.org/an/newpapers/MarGrason.html Strangers in strange lands: non-native prey rely on general information to assess risk from novel predators Recognizing the signs of a predator can mean the difference between living to see another day and becoming another critter’s midday snack. All prey animals, whether a swift-footed deer or a slow-moving snail, use cues from their environment to sense the presence of a threat. It’s what keeps them alive—or at least gives them a shot at getting away. But the specific cues that trigger prey defenses vary depending on the species of prey and their history in the ecosystem, a new University of Washington study finds. The research, appearing in the journal The&nbsp;American Naturalist, analyzed the behavior of seven species of marine snails found in Washington waters—three native and four invasive—and discovered that native and invasive snails use different cues to assess risk.The invasive snails were introduced unintentionally at least a century ago as hitchhikers on imported oysters. In experiments with these invasives, a UW researcher found that they fled quickly (as snails can do) and hid when they smelled chemicals released from crushed snails of the same species—meant to mimic a predator eating their close kin. This is surprising because these so-called “alarm cues” don’t provide the snails with much of a clue as to what or where the danger might be. Panicking with only vague information to go on could even be counter-productive, causing snails to miss their lunch unnecessarily, or actually make them more vulnerable to a predator. By contrast, the three species of native snails didn’t react when they encountered the same situation. Instead, they went about their business until they had multiple sources of information, including from a predator and other prey, before fleeing or hiding. In other words, the fear reactions in native snails were more finely tuned, while the invasive snails jumped ship at the first whiff of a threat. “It’s pretty rare for a distinction between native and invasive species to be as consistent as it is here—which suggests it might hold true in other species and locations,” said author Emily Grason, an invasion ecologist at UW-based Washington Sea Grant who recently completed her doctorate in biology at the UW. This study is the first to compare multiple species and their reactions to threats using many different predator cues. Because the reactions of native and non-native snails split neatly, it suggests there could be a link between sensitivity to alarm cues and invasion success. On one hand, that can keep them from important tasks like eating and mating, but it also can fortify their strength as an invader, Grason explained. “The non-native snails show up and they are just neurotic enough, and a bit wary, and that actually helps them survive in certain situations,” she said. “You end up with invasive snails that hide at the right time, even if they don’t know what the predator is. And that’s exactly what happens when snails show up in a new spot; they are surrounded by predators never encountered before. General wariness might keep them alive.” Grason ran separate lab experiments for each species of snail. Two bins, with flowing seawater, were attached by a pipe, and she manipulated cues of a predation threat in the upstream bin while recording snails’ behavior in the downstream bin. The cues tested for all species included a crab, either hungry or fed, crushed snails of the same species and two other combinations of these factors. The invasive snails’ catchall reaction to signals of danger can help ecologists better understand invasions and predict their impact on ecosystems, which is never easy. “Ultimately, biological invasions are a Pandora’s box because we don’t know what will happen,” Grason said. “Nevertheless, understanding the details of an invasion—especially where there are and aren’t patterns—is important. Thinking about biological invasions in new ways is going to offer us more tools with which to understand and hopefully intervene, or mitigate the impacts on other species.” This study was funded by the UW, the Conchologists of America, the National Shellfisheries Association, the Pacific Northwest Shell Club and the National Oceanic and Atmospheric Administration. For more information, contact Grason at egrason&nbsp;(at)&nbsp;uw.edu. Grason dedicates this research to the memory of the late UW ecologist Robert Paine, who published his seminal work on “keystone species” in the same journal 50 years ago. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Strangers in strange lands: non-native prey rely on general information to assess risk from novel predators </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;">R</span>ecognizing the signs of a predator can mean the difference between living to see another day and becoming another critter&rsquo;s midday snack. All prey animals, whether a swift-footed deer or a slow-moving snail, use cues from their environment to sense the presence of a threat. It&rsquo;s what keeps them alive&mdash;or at least gives them a shot at getting away. But the specific cues that trigger prey defenses vary depending on the species of prey and their history in the ecosystem, a new University of Washington study finds. The research, appearing in the journal <i>The&nbsp;American Naturalist</i>, analyzed the behavior of seven species of marine snails found in Washington waters&mdash;three native and four invasive&mdash;and discovered that native and invasive snails use different cues to assess risk.</p><p>The invasive snails were introduced unintentionally at least a century ago as hitchhikers on imported oysters. In experiments with these invasives, a UW researcher found that they fled quickly (as snails can do) and hid when they smelled chemicals released from crushed snails of the same species—meant to mimic a predator eating their close kin. This is surprising because these so-called “alarm cues” don’t provide the snails with much of a clue as to what or where the danger might be. Panicking with only vague information to go on could even be counter-productive, causing snails to miss their lunch unnecessarily, or actually make them more vulnerable to a predator. </p><p>By contrast, the three species of native snails didn’t react when they encountered the same situation. Instead, they went about their business until they had multiple sources of information, including from a predator and other prey, before fleeing or hiding. In other words, the fear reactions in native snails were more finely tuned, while the invasive snails jumped ship at the first whiff of a threat. “It’s pretty rare for a distinction between native and invasive species to be as consistent as it is here—which suggests it might hold true in other species and locations,” said author <a href="http://emilygrason.weebly.com/research.html">Emily Grason</a>, an invasion ecologist at UW-based Washington Sea Grant who recently completed her doctorate in biology at the UW. </p><p>This study is the first to compare multiple species and their reactions to threats using many different predator cues. Because the reactions of native and non-native snails split neatly, it suggests there could be a link between sensitivity to alarm cues and invasion success. On one hand, that can keep them from important tasks like eating and mating, but it also can fortify their strength as an invader, Grason explained. “The non-native snails show up and they are just neurotic enough, and a bit wary, and that actually helps them survive in certain situations,” she said. “You end up with invasive snails that hide at the right time, even if they don’t know what the predator is. And that’s exactly what happens when snails show up in a new spot; they are surrounded by predators never encountered before. General wariness might keep them alive.” </p><p>Grason ran separate lab experiments for each species of snail. Two bins, with flowing seawater, were attached by a pipe, and she manipulated cues of a predation threat in the upstream bin while recording snails’ behavior in the downstream bin. The cues tested for all species included a crab, either hungry or fed, crushed snails of the same species and two other combinations of these factors. </p><p>The invasive snails’ catchall reaction to signals of danger can help ecologists better understand invasions and predict their impact on ecosystems, which is never easy. “Ultimately, biological invasions are a Pandora’s box because we don’t know what will happen,” Grason said. “Nevertheless, understanding the details of an invasion—especially where there are and aren’t patterns—is important. Thinking about biological invasions in new ways is going to offer us more tools with which to understand and hopefully intervene, or mitigate the impacts on other species.” </p><p>This study was funded by the UW, the Conchologists of America, the National Shellfisheries Association, the Pacific Northwest Shell Club and the National Oceanic and Atmospheric Administration. For more information, contact Grason at egrason&nbsp;(at)&nbsp;uw.edu. Grason dedicates this research to the memory of the late UW ecologist <a href="http://www.journals.uchicago.edu/doi/full/10.1086/689447">Robert Paine</a>, who published his seminal work on &ldquo;keystone species&rdquo; in the same journal 50 years ago. <a href="http://dx.doi.org/10.1086/690217">Read&nbsp;the&nbsp;Article</a></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> Fri, 13 Jan 2017 06:00:00 GMT “A novel, enigmatic basal leafflower moth lineage pollinating a derived leafflower host illustrates the dynamics of host shifts, partner replacement, and apparent co-adaptation in intimate mutualisms” http://amnat.org/an/newpapers/AprLuo.html Moth plays Cupid by spending nearly its whole life inside its tree host, emerging only to assure their reproduction In a study appearing in The American Naturalist, scientists in China and the United States report the discovery of a symbiotic relationship between a tropical tree and a tiny moth which is one of the most intricately interconnected relationships between a plant and its pollinator ever described. Examining dried specimens of the leafflower tree Glochidion lanceolarium collected 80 years earlier, botanist Shixiao Luo noticed something bizarre: dried fruits that burst open to reveal not only seeds, but tiny adult moths. Intrigued, Luo hunted down some live G.&nbsp;lanceolarium trees (the nearest ones were, conveniently, growing wild in the South China Botanical Garden where he works) and, with his colleagues Gang Yao, Ziwei Wang, and Dianxiang Zhang, set about observing these trees’ flowers and fruit over the course of a year to unravel their relationship with the tiny moths. The moths were the species Epicephala lanceolaria, part of a genus which, as adults, pollinates the flowers of Glochidion trees and, as larvae, consumes seeds of the same trees. The relationship between Glochidion trees and Epicephala moths (leafflower moths) had been known to science since 2003. But the relationship between G. lanceolarium and E.&nbsp;lanceolaria was even more intimate and interconnected than that between other known species of leafflower trees and moths. E.&nbsp;lanceolaria caterpillars not only eat the seeds of their host tree, but they also spin their cocoons inside hollow chambers inside the fruit. The adult moths emerge inside these chambers right before the mature fruits split open—explaining the tiny dried moths Luo had found on the herbarium specimens. Instead of producing flowers and fruit continuously throughout the growing season like most of their relatives, G.&nbsp;lanceolarium take a year to develop their flowers into fruit. All fruits ripen at the same time in April, and over the course of a few nights, the fruits split open and the adult moths emerge, mate, and fly to the next year’s newly opened flowers to pollinate them and lay their eggs. In collaboration with David Hembry (University of Arizona), Luo and Wang sequenced DNA from E.&nbsp;lanceolaria and compared it to all known species in the same genus. This analysis revealed an evolutionary enigma: these moths were not part of the same clade that pollinates all other species of Glochidion trees. Rather, they were an unknown, distantly related lineage with no known close relatives—possibly, in fact, more closely related to leafflower moths that pollinate other genera of tropical leafflower trees in Asia (Phyllanthus and Breynia). How G. &nbsp;lanceolarium and its moth came to be associated is mysterious. Most likely, E. &nbsp;lanceolaria represents a lineage that, although ancient, shifted relatively recently onto the ancestor of G. &nbsp;lanceolarium. The moth probably had other close relatives which are either now extinct, or not yet discovered. This work highlights the extent to which highly intimate and coevolved associations may be more evolutionarily dynamic than had been previously realized, and how much remains to be discovered about the biodiversity and natural history of tropical Asia. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Moth plays Cupid by spending nearly its whole life inside its tree host, emerging only to assure their reproduction </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 a study appearing in <i>The American Naturalist</i>, scientists in China and the United States report the discovery of a symbiotic relationship between a tropical tree and a tiny moth which is one of the most intricately interconnected relationships between a plant and its pollinator ever described. </p> <p> Examining dried specimens of the leafflower tree <i>Glochidion lanceolarium</i> collected 80 years earlier, botanist Shixiao Luo noticed something bizarre: dried fruits that burst open to reveal not only seeds, but tiny adult moths. Intrigued, Luo hunted down some live <i>G.&nbsp;lanceolarium</i> trees (the nearest ones were, conveniently, growing wild in the South China Botanical Garden where he works) and, with his colleagues Gang Yao, Ziwei Wang, and Dianxiang Zhang, set about observing these trees’ flowers and fruit over the course of a year to unravel their relationship with the tiny moths. </p> <p> The moths were the species <i>Epicephala lanceolaria</i>, part of a genus which, as adults, pollinates the flowers of <i>Glochidion</i> trees and, as larvae, consumes seeds of the same trees. The relationship between <i>Glochidion</i> trees and <i>Epicephala</i> moths (leafflower moths) had been known to science since 2003. But the relationship between <i>G. lanceolarium</i> and <i>E.&nbsp;lanceolaria</i> was even more intimate and interconnected than that between other known species of leafflower trees and moths. <i>E.&nbsp;lanceolaria</i> caterpillars not only eat the seeds of their host tree, but they also spin their cocoons inside hollow chambers inside the fruit. The adult moths emerge inside these chambers right before the mature fruits split open—explaining the tiny dried moths Luo had found on the herbarium specimens. Instead of producing flowers and fruit continuously throughout the growing season like most of their relatives, <i>G.&nbsp;lanceolarium</i> take a year to develop their flowers into fruit. All fruits ripen at the same time in April, and over the course of a few nights, the fruits split open and the adult moths emerge, mate, and fly to the next year’s newly opened flowers to pollinate them and lay their eggs. </p> <p> In collaboration with David Hembry (University of Arizona), Luo and Wang sequenced DNA from <i>E.&nbsp;lanceolaria</i> and compared it to all known species in the same genus. This analysis revealed an evolutionary enigma: these moths were not part of the same clade that pollinates all other species of <i>Glochidion</i> trees. Rather, they were an unknown, distantly related lineage with no known close relatives—possibly, in fact, more closely related to leafflower moths that pollinate other genera of tropical leafflower trees in Asia (<i>Phyllanthus</i> and <i>Breynia</i>). How <i>G. &nbsp;lanceolarium</i> and its moth came to be associated is mysterious. Most likely, <i>E. &nbsp;lanceolaria</i> represents a lineage that, although ancient, shifted relatively recently onto the ancestor of <i>G. &nbsp;lanceolarium</i>. The moth probably had other close relatives which are either now extinct, or not yet discovered. This work highlights the extent to which highly intimate and coevolved associations may be more evolutionarily dynamic than had been previously realized, and how much remains to be discovered about the biodiversity and natural history of tropical Asia. <a href="http://dx.doi.org/10.1086/690623">Read&nbsp;the&nbsp;Article</a> </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, 13 Jan 2017 06:00:00 GMT “Surviving in a cosexual world: a cost-benefit analysis of dioecy in tropical trees” http://amnat.org/an/newpapers/MarBruijning.html Dioecious species survive in a cosexual world due to increased fecundity and low overall costs Most tree species are hermaphroditic, meaning that individuals carry flowers with both male (stamens) and female (pistil) parts. In contrast, in dioecious species, individuals have either male or female flowers. This reduces the number of individuals in a population that can produce seeds, as only female flowers develop seeds. How dioecious species can compensate for this demographic cost has been a longstanding challenge in ecology, and was already recognized by Darwin: “There is much difficulty in understanding why hermaphroditic plants should ever have been rendered dioecious” (Darwin, 1877). Female trees must compensate for costs of having males in a population, but how do they do this? A team of researchers from Radboud University (the Netherlands), the Smithsonian Tropical Research Institute (Panama), Yale University, and the University of California (both USA) set out to test this. They used long-term data on more than 100 tree species from a tropical tree community on Barro Colorado Island (Panama). They combined data on seeds, seedlings, saplings, and adult trees to estimate growth, survival, and reproduction across the entire life cycle. Their results show that female trees compensate for the costs of males by producing almost twice as many seeds compared to hermaphroditic trees, perhaps because the latter do not carry the costs of male reproduction. When combining the costs and benefits of dioecy into a population model, they revealed that no net costs of dioecy existed. The model revealed another surprise: the cost of having males was far smaller than expected because tree survival rather than reproduction was overwhelmingly important for population maintenance. These results together can explain the persistence of dioecious species in a cosexual world, as well as the long-standing puzzle observed by Darwin. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Dioecious species survive in a cosexual world due to increased fecundity and low overall costs </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;">M</span>ost tree species are hermaphroditic, meaning that individuals carry flowers with both male (stamens) and female (pistil) parts. In contrast, in dioecious species, individuals have either male or female flowers. This reduces the number of individuals in a population that can produce seeds, as only female flowers develop seeds. How dioecious species can compensate for this demographic cost has been a longstanding challenge in ecology, and was already recognized by Darwin: “There is much difficulty in understanding why hermaphroditic plants should ever have been rendered dioecious” (Darwin, 1877). Female trees must compensate for costs of having males in a population, but how do they do this? </p><p>A team of researchers from Radboud University (the Netherlands), the Smithsonian Tropical Research Institute (Panama), Yale University, and the University of California (both USA) set out to test this. They used long-term data on more than 100 tree species from a tropical tree community on Barro Colorado Island (Panama). They combined data on seeds, seedlings, saplings, and adult trees to estimate growth, survival, and reproduction across the entire life cycle. </p><p>Their results show that female trees compensate for the costs of males by producing almost twice as many seeds compared to hermaphroditic trees, perhaps because the latter do not carry the costs of male reproduction. When combining the costs and benefits of dioecy into a population model, they revealed that no net costs of dioecy existed. The model revealed another surprise: the cost of having males was far smaller than expected because tree survival rather than reproduction was overwhelmingly important for population maintenance. These results together can explain the persistence of dioecious species in a cosexual world, as well as the long-standing puzzle observed by Darwin. <a href="http://dx.doi.org/10.1086/690137">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 11 Jan 2017 06:00:00 GMT “From individual to group territoriality: Competitive environments promote the evolution of sociality” http://amnat.org/an/newpapers/MarPort.html Most of us might think that competition generates aggression. A study appearing in The American Naturalist shows, however, that this need not be the case – at least not in territorial animals, where competition can actually pave the way for the evolution of sociality. Male Verreaux’s sifaka can engage in fierce fights over territories, but they can also be fairly tolerant towards each other. As a result, some males defend exclusive access to small groups of females, whereas others share their territories with other males, and drive off competitors together. “At first glance, it looks like these lemurs are caught in an evolutionary transition between individual territoriality and sociality,” says Markus Port, first author of the study, “but our analyses show that social systems like the one of Verreaux’s sifaka can actually be a stable endpoint of evolution.” Port and his colleagues Oliver Schülke and Julia Ostner from Göttingen University in Germany have developed a game-theoretic model, in which they show that these ‘mixed equilibria’ can be the result of a coevolutionary feedback between the behavior of territory owners and outsiders, where owners adjust their degree of tolerance to the level of aggression imposed on them by outsiders and vice versa. Perhaps surprisingly, their analyses also show that elevated competition leads to more tolerance and lower levels of aggression. “The reason is that strong competition puts owners in strong demand for helpers to help them defend their territories,” explains Port, “such that tolerant owners and peaceful outsiders outperform mutually aggressive conspecifics.” Strong competition, therefore, does not necessarily select for elevated territorial aggression, but can rather drive the evolution of sociality. Read&nbsp;the&nbsp;Article 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;">M</span>ost of us might think that competition generates aggression. A study appearing in <i>The American Naturalist</i> shows, however, that this need not be the case – at least not in territorial animals, where competition can actually pave the way for the evolution of sociality. </p><p>Male Verreaux’s sifaka can engage in fierce fights over territories, but they can also be fairly tolerant towards each other. As a result, some males defend exclusive access to small groups of females, whereas others share their territories with other males, and drive off competitors together. “At first glance, it looks like these lemurs are caught in an evolutionary transition between individual territoriality and sociality,” says Markus Port, first author of the study, “but our analyses show that social systems like the one of Verreaux’s sifaka can actually be a stable endpoint of evolution.” </p><p>Port and his colleagues Oliver Schülke and Julia Ostner from Göttingen University in Germany have developed a game-theoretic model, in which they show that these ‘mixed equilibria’ can be the result of a coevolutionary feedback between the behavior of territory owners and outsiders, where owners adjust their degree of tolerance to the level of aggression imposed on them by outsiders and vice versa. Perhaps surprisingly, their analyses also show that elevated competition leads to more tolerance and lower levels of aggression. </p><p>“The reason is that strong competition puts owners in strong demand for helpers to help them defend their territories,” explains Port, “such that tolerant owners and peaceful outsiders outperform mutually aggressive conspecifics.” Strong competition, therefore, does not necessarily select for elevated territorial aggression, but can rather drive the evolution of sociality. <a href="http://dx.doi.org/10.1086/690218">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 11 Jan 2017 06:00:00 GMT ASN Awards for Support of Regional Meetings in Ecology, Evolution, and Behavior http://amnat.org/announcements/RegionalWkshpCall.html The American Society of Naturalists solicits proposals from organizers of regional meetings in the fields of ecology, evolution and behavior. The purpose of these small awards is to promote increased participation in regional meetings that fall along the research interests supported by the ASN and to use this support as a way of recruiting new membership to ASN. The awards typically provide subsidized registration for ASN members at these regional meetings. Please note that these awards are not intended to support workshops. Previous awardees have included meetings such as SEEPEG, SEEC, EVO-WIBO, and OE3C. Organizers of regional meetings should submit a brief proposal describing the research focus of the meeting for which funds are requested as well as details of the meeting such as anticipated number of participants, meeting venue and dates. Instructions:&nbsp;Proposals should include two components. One should clearly describe the (1) overlap of the regional meeting with ASN research interests, (2) extent that the support would reach out to new audiences to grow ASN&#39;s membership, and (3) potential size of the impact on ASN membership. The second component should include a brief budget justifying the amount requested and detailing how the funds will be used. To standardize the applications, there is a strict one-page limit (US Letter size paper, 1” margins, standard [e.g., Times] 12-point font, and no more than six lines per inch) for each component (i.e., 1 page for proposal, 1 page for budget description and use of funds). We anticipate funding 4-6 awards, typically valued at $2000-$3000. Please send proposals to the ASN Regional Society Liaison Committee Chair Rebecca Kimball (rkimball@ufl.edu) by February 15. <p>The American Society of Naturalists solicits proposals from organizers of regional meetings in the fields of ecology, evolution and behavior. The purpose of these small awards is to promote increased participation in regional meetings that fall along the research interests supported by the ASN and to use this support as a way of recruiting new membership to ASN. The awards typically provide subsidized registration for ASN members at these regional meetings. Please note that these awards are not intended to support workshops. Previous awardees have included meetings such as SEEPEG, SEEC, EVO-WIBO, and OE3C.</p> <p>Organizers of regional meetings should submit a brief proposal describing the research focus of the meeting for which funds are requested as well as details of the meeting such as anticipated number of participants, meeting venue and dates.</p> <p><strong>Instructions:</strong>&nbsp;Proposals should include two components. One should clearly describe the (1) overlap of the regional meeting with ASN research interests, (2) extent that the support would reach out to new audiences to grow ASN&#39;s membership, and (3) potential size of the impact on ASN membership. The second component should include a brief budget justifying the amount requested and detailing how the funds will be used. To standardize the applications, there is a strict one-page limit (US Letter size paper, 1&rdquo; margins, standard [e.g., Times] 12-point font, and no more than six lines per inch) for each component (i.e., 1 page for proposal, 1 page for budget description and use of funds). We anticipate funding 4-6 awards, typically valued at $2000-$3000.</p> <p><span style="line-height: 1.6em;">Please send proposals to the ASN Regional Society Liaison Committee Chair Rebecca Kimball (<a href="mailto:rkimball@ufl.edu?subject=ASN%20Regional%20Meeting%20Support">rkimball@ufl.edu</a>) by February 15.</span></p> Fri, 06 Jan 2017 06:00:00 GMT “What explains patterns of diversification and richness among animal phyla?” http://amnat.org/an/newpapers/MarJezkova.html Three traits explain most of the variation in the diversity of animal phyla, representing >80% of all known species A&nbsp;new study helps explain why different groups of animals have such different numbers of species, and how this is related to differences in their body forms and ways of life. All animal species are divided among ~30 phyla, but these phyla differ dramatically in how many species they contain, from a single species to more than 1.2 million (insects and relatives). However, the explanation for the remarkable variation in biodiversity among animal phyla remains largely unknown. Animals also have incredible variation in their body shapes and ways of life. For example, animals include plant-like, immobile marine phyla that lack heads, eyes, limbs, and complex organs (sponges), parasitic worms that live inside other organisms (e.g. nematodes, platyhelminths), and phyla with eyes, skeletons, limbs, and complex organs that dominate the land in terms of species numbers (arthropods) and body size (chordates). A fundamental but unresolved problem is whether the basic biology of these phyla is related to their species numbers. For example, does having a head, limbs, and eyes allow some groups to be more successful and thus have greater species numbers? In a new study, researchers from the University of Arizona have helped resolve this problem. They assembled a database of 18 traits, including traits related to anatomy, reproduction, and ecology. They then tested how each trait was related to the number of species in each phylum, and to how quickly species in each phylum multiplied over time (diversification). They found that just three traits explained most variation in diversification and species numbers among phyla: the most successful phyla have a skeleton (either internal or external), live on land (instead of in the ocean), and parasitize other organisms. They also found that many dramatic traits had surprisingly little impact on diversification and species numbers, such as having a head, limbs, and complex organ systems for circulation and digestion. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Three traits explain most of the variation in the diversity of animal phyla, representing >80% of all known species </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;new study helps explain why different groups of animals have such different numbers of species, and how this is related to differences in their body forms and ways of life. </p><p> All animal species are divided among ~30 phyla, but these phyla differ dramatically in how many species they contain, from a single species to more than 1.2 million (insects and relatives). However, the explanation for the remarkable variation in biodiversity among animal phyla remains largely unknown. Animals also have incredible variation in their body shapes and ways of life. For example, animals include plant-like, immobile marine phyla that lack heads, eyes, limbs, and complex organs (sponges), parasitic worms that live inside other organisms (e.g. nematodes, platyhelminths), and phyla with eyes, skeletons, limbs, and complex organs that dominate the land in terms of species numbers (arthropods) and body size (chordates). A fundamental but unresolved problem is whether the basic biology of these phyla is related to their species numbers. For example, does having a head, limbs, and eyes allow some groups to be more successful and thus have greater species numbers? </p><p> In a new study, researchers from the University of Arizona have helped resolve this problem. They assembled a database of 18 traits, including traits related to anatomy, reproduction, and ecology. They then tested how each trait was related to the number of species in each phylum, and to how quickly species in each phylum multiplied over time (diversification). They found that just three traits explained most variation in diversification and species numbers among phyla: the most successful phyla have a skeleton (either internal or external), live on land (instead of in the ocean), and parasitize other organisms. They also found that many dramatic traits had surprisingly little impact on diversification and species numbers, such as having a head, limbs, and complex organ systems for circulation and digestion. <a href="http://dx.doi.org/10.1086/690194">Read&nbsp;the&nbsp;Article</a> </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, 03 Jan 2017 06:00:00 GMT “Social information on fear and food drives animal grouping and fitness” http://amnat.org/an/newpapers/MarGil.html Applications like Facebook and Twitter show us, on a daily basis, the power of social networks to influence individual behavior. While wild animals do not surf the web, they are connected with other individuals in shared landscapes, and “share information” through their behavior. But how does this information affect surrounding animals? A new study appearing in The American Naturalist reveals that the information shared through animal social networks can provide profound fitness advantages to various animals across a range of environments. Using mathematical simulations, Mike Gil of the University of California, Davis, and co-authors Zachary Emberts, Harrison Jones, and Colette St. Mary of the University of Florida show that these advantages arise because information generated incidentally or intentionally from the actions of an individual provides others with insights on how to survive in often unforgiving natural settings. For example, an animal fleeing from a predator or chomping away at a patch of food can alert similar animals in the vicinity of a shared threat or opportunity. The researchers further found that information sharing among animals promotes animal group formation, but often favors the formation of mixed-species groups, in which members overlap less in the kind of food they eat but still share predators. These findings point to information sharing as a fundamental driver of animal group formation, shedding new light on the age-old question of why animal groups are so common in nature. Read&nbsp;the&nbsp;Article 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;">A</span>pplications like Facebook and Twitter show us, on a daily basis, the power of social networks to influence individual behavior. While wild animals do not surf the web, they are connected with other individuals in shared landscapes, and “share information” through their behavior. But how does this information affect surrounding animals? </p><p>A new study appearing in <i>The American Naturalist</i> reveals that the information shared through animal social networks can provide profound fitness advantages to various animals across a range of environments. Using mathematical simulations, Mike Gil of the University of California, Davis, and co-authors Zachary Emberts, Harrison Jones, and Colette St. Mary of the University of Florida show that these advantages arise because information generated incidentally or intentionally from the actions of an individual provides others with insights on how to survive in often unforgiving natural settings. </p><p>For example, an animal fleeing from a predator or chomping away at a patch of food can alert similar animals in the vicinity of a shared threat or opportunity. </p><p>The researchers further found that information sharing among animals promotes animal group formation, but often favors the formation of mixed-species groups, in which members overlap less in the kind of food they eat but still share predators. These findings point to information sharing as a fundamental driver of animal group formation, shedding new light on the age-old question of why animal groups are so common in nature. <a href="http://dx.doi.org/10.1086/690055">Read&nbsp;the&nbsp;Article</a> </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, 03 Jan 2017 06:00:00 GMT “The evolution of reproductive phenology in broadcast spawners: frequency-dependent sexually antagonistic selection and the maintenance of polymorphism” http://amnat.org/an/newpapers/FebOlito.html Sexual conflict in broadcast spawners: females want more kids, males want more kids than the other guys Choosing the best time to reproduce is a major challenge faced by all organisms. For broadcast spawning species that release eggs and sperm into water, the consequences of getting reproductive timing wrong can be profound for both sexes. If females spawn when there are too few mates, there is not enough sperm to fertilize all their eggs. If females spawn when there are too many mates, egg mortality due to polyspermy (where eggs are fertilized by multiple sperm) can be severe. For males, as more individuals spawn at the same time, there are more eggs but there are also more competitors. On top of all of this, there are often better times to spawn than others because environmental conditions may sometimes be hostile to offspring. Broadcast spawners must therefore balance many conflicting factors when it comes to timing their reproduction, and it’s unclear what factors matter the most. In their article appearing in The&nbsp;American Naturalist, the authors use mathematical models to show that males and females often prefer to spawn at different times, depending on how many individuals are participating in spawning events. Females favor spawning at the specific times that maximize egg fertilization and offspring survival. In contrast, males often favor spawning at multiple times as a means of competing more effectively against other males for fertilizations, even if this results in lower overall fertilization success of the population. These predictions help explain several well-documented, yet counterintuitive, patterns in aquatic species, including unexpectedly long spawning seasons, different spawning behaviors by males and females, and spawning during poor environmental conditions. The models also provide a fascinating example of how conflict between the sexes over a shared trait (reproductive timing) can emerge from fundamental processes of egg fertilization, the timing of reproduction, and the density of spawning individuals. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Sexual conflict in broadcast spawners: females want more kids, males want more kids than the other guys </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>hoosing the best time to reproduce is a major challenge faced by all organisms. For broadcast spawning species that release eggs and sperm into water, the consequences of getting reproductive timing wrong can be profound for both sexes. If females spawn when there are too few mates, there is not enough sperm to fertilize all their eggs. If females spawn when there are too many mates, egg mortality due to polyspermy (where eggs are fertilized by multiple sperm) can be severe. For males, as more individuals spawn at the same time, there are more eggs but there are also more competitors. On top of all of this, there are often better times to spawn than others because environmental conditions may sometimes be hostile to offspring. Broadcast spawners must therefore balance many conflicting factors when it comes to timing their reproduction, and it&rsquo;s unclear what factors matter the most.</p> <p>In their article appearing in <i>The&nbsp;American Naturalist</i>, the authors use mathematical models to show that males and females often prefer to spawn at different times, depending on how many individuals are participating in spawning events. Females favor spawning at the specific times that maximize egg fertilization and offspring survival. In contrast, males often favor spawning at multiple times as a means of competing more effectively against other males for fertilizations, even if this results in lower overall fertilization success of the population. These predictions help explain several well-documented, yet counterintuitive, patterns in aquatic species, including unexpectedly long spawning seasons, different spawning behaviors by males and females, and spawning during poor environmental conditions. The models also provide a fascinating example of how conflict between the sexes over a shared trait (reproductive timing) can emerge from fundamental processes of egg fertilization, the timing of reproduction, and the density of spawning individuals. <a href="http://dx.doi.org/10.1086/690010">Read&nbsp;the&nbsp;Article</a></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, 29 Dec 2016 06:00:00 GMT “Age-dependent modulation of songbird summer feather molt by temporal and functional constraints” http://amnat.org/an/newpapers/FebKiat.html Songbirds molt their feathers on an annual basis because feathers get worn with time due to exposure to UV radiation and other environmental factors. Feather molt is a timely undertaking that is considered among the three most energy-demanding processes in the life cycle of birds, and as such should be made at the most convenient time for the bird. Songbird feather molt usually takes place during fall, just after breeding and before migration, and might be constrained by these activities. To deal with time pressure, passerines may shorten their molt duration by only replacing part of the plumage, through increasing the speed of molt, or by postponing the renewal of some or all the plumage to a later season (i.e., from the summer to the over-wintering period). Yosef Kiat and Nir Sapir from the Hebrew University and the University of Haifa, Israel, used a comparative approach by measuring 12,349 individuals from 134 passerine species in different sites across Israel and two museum bird collections in Israel and the UK to explore how feather molt of juvenile and adult passerines is evolutionarily modulated under time constraints. The results indicate that breeding at northern latitudes and long-distance migration limit the time available for molt and that the consequences of these time constraints were age-dependent. While the duration of adult summer molt decreased, the extent, rather than the duration, of juvenile molt declined under time constraints. The findings suggest that two different adaptations to deal with time pressure have evolved in passerines, and that they are employed depending on bird age. This study highlights the importance of considering time constraints for better understanding the evolution of life history processes and their consequences throughout the annual routine. Read&nbsp;the&nbsp;Article 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;">S</span>ongbirds molt their feathers on an annual basis because feathers get worn with time due to exposure to UV radiation and other environmental factors. Feather molt is a timely undertaking that is considered among the three most energy-demanding processes in the life cycle of birds, and as such should be made at the most convenient time for the bird. Songbird feather molt usually takes place during fall, just after breeding and before migration, and might be constrained by these activities. To deal with time pressure, passerines may shorten their molt duration by only replacing part of the plumage, through increasing the speed of molt, or by postponing the renewal of some or all the plumage to a later season (i.e., from the summer to the over-wintering period). Yosef Kiat and Nir Sapir from the Hebrew University and the University of Haifa, Israel, used a comparative approach by measuring 12,349 individuals from 134 passerine species in different sites across Israel and two museum bird collections in Israel and the UK to explore how feather molt of juvenile and adult passerines is evolutionarily modulated under time constraints. The results indicate that breeding at northern latitudes and long-distance migration limit the time available for molt and that the consequences of these time constraints were age-dependent. While the duration of adult summer molt decreased, the extent, rather than the duration, of juvenile molt declined under time constraints. The findings suggest that two different adaptations to deal with time pressure have evolved in passerines, and that they are employed depending on bird age. This study highlights the importance of considering time constraints for better understanding the evolution of life history processes and their consequences throughout the annual routine. <a href="http://dx.doi.org/10.1086/690031">Read&nbsp;the&nbsp;Article</a> </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, 29 Dec 2016 06:00:00 GMT “Radiating despite a lack of character: ecological divergence among closely related, morphologically similar honeyeaters (Aves: Meliphagidae) co-occurring in arid Australian environments” http://amnat.org/an/newpapers/FebMiller.html Closely related honeyeaters have diverged in ecology despite conserved morphology Usually a bird’s beak offers clues to the type of food it eats. A hummingbird’s long, slender beak is perfect for sipping nectar. The crossbill uses its unique bill to extricate pinecone seeds. But sometimes, appearances can be deceiving, according to research on Australian honeyeaters appearing in The American Naturalist. Cornell Lab of Ornithology researchers Eliot Miller and Sarah Wagner crisscrossed the Australian continent to compare the diet, foraging behavior, and bill shape of the 75 species of honeyeaters that live there. Like hummingbirds, many honeyeaters take nectar, but some species also take insects and fruit. Their beaks generally reflect these species-specific dietary differences. Though honeyeaters originally occupied Australian rainforests millions of years ago, that habitat is now found only in a slim margin along the coast. As a result, almost half of the species of modern honeyeaters live in the desert, which now makes up a significant portion of the continent—over 50% of the landmass receives less than a foot of rain per year. “By and large, honeyeaters that live in the desert resemble their forest relatives in diet and foraging behavior. There are leaf-gleaning insect-eaters, nectar feeders, and those that feast on fruit. There is even a group of species that forages on bare ground like a little inland sandpiper. But morphologically, these species are only a subset of the diversity found in forests. These desert honeyeater species are using their ancestral morphologies in very different ways to survive.” For example, for a recent lecture, Miller stitched together a photograph of a Gibberbird and a photograph of a Green-backed Honeyeater into a single image of what appeared to be two individuals of the same species. But while the Green-backed Honeyeater gleans insects from leaves in the rainforest canopy, the Gibberbird wanders and feeds in the nearly bare expanses of inland gravel plain known as gibber. For their study, the researchers found at least 20 individuals of all but one of the honeyeater species in Australia. For each of these birds they recorded details of its foraging behavior and surrounding habitat. They then used museum specimens to measure beak, wing, tail, leg, and foot characteristics of at least 6 individuals of each honeyeater species. Comparing the two datasets, they found that desert honeyeaters appear to do more with less. The researchers’ quantitative natural history data, now publicly available on Dryad, allowed them to address their questions. “Across the board, the correspondence between a species’ morphology and its ecology is generally good,” Miller said. “But it appears that in the desert, ecological opportunity has allowed Australian honeyeaters to expand their foraging niches.” Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b><!-- Radiating despite a lack of character: -->Closely related honeyeaters have diverged in ecology despite conserved morphology </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;">U</span>sually a bird’s beak offers clues to the type of food it eats. A hummingbird’s long, slender beak is perfect for sipping nectar. The crossbill uses its unique bill to extricate pinecone seeds. But sometimes, appearances can be deceiving, according to research on Australian honeyeaters appearing in <i>The American Naturalist</i>. </p><p>Cornell Lab of Ornithology researchers Eliot Miller and Sarah Wagner crisscrossed the Australian continent to compare the diet, foraging behavior, and bill shape of the 75 species of honeyeaters that live there. Like hummingbirds, many honeyeaters take nectar, but some species also take insects and fruit. Their beaks generally reflect these species-specific dietary differences. </p><p>Though honeyeaters originally occupied Australian rainforests millions of years ago, that habitat is now found only in a slim margin along the coast. As a result, almost half of the species of modern honeyeaters live in the desert, which now makes up a significant portion of the continent—over 50% of the landmass receives less than a foot of rain per year. </p><p>“By and large, honeyeaters that live in the desert resemble their forest relatives in diet and foraging behavior. There are leaf-gleaning insect-eaters, nectar feeders, and those that feast on fruit. There is even a group of species that forages on bare ground like a little inland sandpiper. But morphologically, these species are only a subset of the diversity found in forests. These desert honeyeater species are using their ancestral morphologies in very different ways to survive.” </p><p>For example, for a recent lecture, Miller stitched together a photograph of a Gibberbird and a photograph of a Green-backed Honeyeater into a single image of what appeared to be two individuals of the same species. But while the Green-backed Honeyeater gleans insects from leaves in the rainforest canopy, the Gibberbird wanders and feeds in the nearly bare expanses of inland gravel plain known as gibber. </p><p>For their study, the researchers found at least 20 individuals of all but one of the honeyeater species in Australia. For each of these birds they recorded details of its foraging behavior and surrounding habitat. They then used museum specimens to measure beak, wing, tail, leg, and foot characteristics of at least 6 individuals of each honeyeater species. Comparing the two datasets, they found that desert honeyeaters appear to do more with less. </p><p>The researchers’ quantitative natural history data, now publicly available on Dryad, allowed them to address their questions. “Across the board, the correspondence between a species’ morphology and its ecology is generally good,” Miller said. “But it appears that in the desert, ecological opportunity has allowed Australian honeyeaters to expand their foraging niches.” <a href="http://dx.doi.org/10.1086/690008">Read&nbsp;the&nbsp;Article</a> </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, 29 Dec 2016 06:00:00 GMT “Selfing, local mate competition, and reinforcement” http://amnat.org/an/newpapers/FebRausher-A.html Abstract Reinforcement can contribute to speciation by increasing the strength of prezygotic isolating mechanisms. Theoretical analyses over the past two decades have demonstrated that conditions for reinforcement are not unduly restrictive, and empirical investigations have documented over a dozen likely cases, indicating it may be a reasonably common phenomenon in nature. Largely uncharacterized, however, is the diversity of biological scenarios that can create the reduced hybrid fitness that drives reinforcement. Here I examine one such scenario—the evolution of the “selfing syndrome” (a suite of characters including reductions in flower size, and in nectar, pollen and scent production), in highly selfing plant species. Using a 4-locus model, where the loci are (1) a discrimination locus, (2) a target-of-discimination locus, (3) a pollen-production locus, and (4) a selfing-rate locus, I determine the conditions under which this syndrome can favor reinforcement, an increase in discrimination through change at locus (1), in an outcrossing species that experiences gene flow from a highly selfing species. In the absence of both linkage disequilibrium between loci and pollen discounting, reinforcement can occur, but only in a very small fraction of parameter combinations examined. Moderate linkage (r&nbsp;=&nbsp;0.1) between one pair of loci increases this fraction by a factor between moderately, depending on which two loci are linked. Pollen discounting (a reduction in pollen exported to other plants due to increased selfing), by contrast, can increase the fraction of parameter combinations that result in reinforcement substantially. The evolution of reduced pollen production in highly selfing species thus facilitates reinforcement, especially if substantial pollen discounting is associated with selfing. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <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>einforcement can contribute to speciation by increasing the strength of prezygotic isolating mechanisms. Theoretical analyses over the past two decades have demonstrated that conditions for reinforcement are not unduly restrictive, and empirical investigations have documented over a dozen likely cases, indicating it may be a reasonably common phenomenon in nature. Largely uncharacterized, however, is the diversity of biological scenarios that can create the reduced hybrid fitness that drives reinforcement. Here I examine one such scenario&mdash;the evolution of the &ldquo;selfing syndrome&rdquo; (a suite of characters including reductions in flower size, and in nectar, pollen and scent production), in highly selfing plant species. Using a 4-locus model, where the loci are (1) a discrimination locus, (2) a target-of-discimination locus, (3) a pollen-production locus, and (4) a selfing-rate locus, I determine the conditions under which this syndrome can favor reinforcement, an increase in discrimination through change at locus (1), in an outcrossing species that experiences gene flow from a highly selfing species. In the absence of both linkage disequilibrium between loci and pollen discounting, reinforcement can occur, but only in a very small fraction of parameter combinations examined. Moderate linkage (<i>r</i>&nbsp;=&nbsp;0.1) between one pair of loci increases this fraction by a factor between moderately, depending on which two loci are linked. Pollen discounting (a reduction in pollen exported to other plants due to increased selfing), by contrast, can increase the fraction of parameter combinations that result in reinforcement substantially. The evolution of reduced pollen production in highly selfing species thus facilitates reinforcement, especially if substantial pollen discounting is associated with selfing. <a href="http://dx.doi.org/10.1086/690009">Read&nbsp;the&nbsp;Article</a> </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, 29 Dec 2016 06:00:00 GMT “Helping relatives survive and reproduce: inclusive fitness and reproductive value in brood parasitism” http://amnat.org/an/newpapers/FebAndersson.html Some females lay eggs in nests of other females of same species, and can gain fitness if the parasite is a relative In many egg-laying animals, parasitic females increase their reproduction by laying eggs in nests of other females, to the disadvantage of the host. But if the females are related, parasitism can be genetically advantageous also for the host. In conspecific brood parasitism some females lay eggs parasitically in nests of other females of the same species, ‘hosts’ that alone take care of the joint brood. Being parasitized usually impairs the reproduction of the host. But mathematical models suggest that a host can gain a genetic advantage if parasitized by a relative whose reproduction or survival is thereby increased, as suggested by Hamilton’s rule. These predictions are explored in waterfowl, which differ from other birds in that host and parasite females are often related. Estimates based on life history data from common eiders and other ducks suggest that hosts can increase their genetic success (inclusive fitness) if parasitized by a close relative. The largest gains can be achieved through increased parasite reproduction, but gain is also possible through higher survival of parasites that avoid increased predation and other risks of nesting. Being parasitized can be particularly favorable for females with small own clutches, hosting eggs from young related parasites with high reproductive value. The research, from the University of Gothenburg, suggests that being ‘parasitized’ in waterfowl is sometimes neutral or even advantageous owing to genetic benefits to host as well as parasite, contributing to evolution of frequent brood parasitism in these birds. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Some females lay eggs in nests of other females of same species, and can gain fitness if the parasite is a relative </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 many egg-laying animals, parasitic females increase their reproduction by laying eggs in nests of other females, to the disadvantage of the host. But if the females are related, parasitism can be genetically advantageous also for the host. </p> <p>In conspecific brood parasitism some females lay eggs parasitically in nests of other females of the same species, ‘hosts’ that alone take care of the joint brood. Being parasitized usually impairs the reproduction of the host. But mathematical models suggest that a host can gain a genetic advantage if parasitized by a relative whose reproduction or survival is thereby increased, as suggested by Hamilton’s rule. </p><p>These predictions are explored in waterfowl, which differ from other birds in that host and parasite females are often related. Estimates based on life history data from common eiders and other ducks suggest that hosts can increase their genetic success (inclusive fitness) if parasitized by a close relative. The largest gains can be achieved through increased parasite reproduction, but gain is also possible through higher survival of parasites that avoid increased predation and other risks of nesting. Being parasitized can be particularly favorable for females with small own clutches, hosting eggs from young related parasites with high reproductive value. The research, from the University of Gothenburg, suggests that being ‘parasitized’ in waterfowl is sometimes neutral or even advantageous owing to genetic benefits to host as well as parasite, contributing to evolution of frequent brood parasitism in these birds. <a href="http://dx.doi.org/10.1086/689991">Read&nbsp;the&nbsp;Article</a> </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, 15 Dec 2016 06:00:00 GMT “The size-dependence of phytoplankton growth rates: a trade-off between nutrient uptake and metabolism” http://amnat.org/an/newpapers/FebWard-A.html Slow growth of tiny organisms relative to the metabolic theory of ecology is attributed to a key physiological trade-off Abstract Rates of metabolism and population growth are often assumed to decrease universally with increasing organism size. Recent observations have shown, however, that maximum population growth rates among phytoplankton smaller than ~6 microns in diameter tend to increase with organism size. Here we bring together observations and theory to demonstrate that the observed change in slope is attributable to a key trade-off between nutrient uptake and the potential rate of internal metabolism. Specifically, we apply an established model of phytoplankton growth to explore a trade-off between the ability of cells to replenish their internal quota (which increases with size), and their ability to synthesise new biomass (which decreases with size). Contrary to the metabolic theory of ecology, these results demonstrate that rates of resource acquisition, rather than metabolism, provide the primary physiological constraint on the growth rates of some of the smallest and most numerically abundant photosynthetic organisms on Earth. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Slow growth of tiny organisms relative to the metabolic theory of ecology is attributed to a key physiological trade-off </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;">R</span>ates of metabolism and population growth are often assumed to decrease universally with increasing organism size. Recent observations have shown, however, that maximum population growth rates among phytoplankton smaller than ~6 microns in diameter tend to increase with organism size. Here we bring together observations and theory to demonstrate that the observed change in slope is attributable to a key trade-off between nutrient uptake and the potential rate of internal metabolism. Specifically, we apply an established model of phytoplankton growth to explore a trade-off between the ability of cells to replenish their internal quota (which increases with size), and their ability to synthesise new biomass (which decreases with size). Contrary to the metabolic theory of ecology, these results demonstrate that rates of resource acquisition, rather than metabolism, provide the primary physiological constraint on the growth rates of some of the smallest and most numerically abundant photosynthetic organisms on Earth. <a href="http://dx.doi.org/10.1086/689992">Read&nbsp;the&nbsp;Article</a> </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, 12 Dec 2016 06:00:00 GMT “Living on the edge: parasite prevalence changes dramatically across a range edge in an invasive gecko” http://amnat.org/an/newpapers/FebCoates-A.html Parasite prevalence shifts dramatically across a range edge in geckos Abstract Species interactions can determine range limits, and parasitism is the most intimate of such interactions. Intriguingly, the very conditions on range edges likely change host-parasite dynamics in non-trivial ways. Range edges are often associated with clines in host density, and with environmental transitions, both of which may affect parasite transmission. On advancing range edges, founder events and fitness/dispersal costs of parasitism may also cause parasites to be lost on range edges. Here we examine the prevalence of three species of parasite across the range edge of an invasive gecko, Hemidactylus frenatus, in north-eastern Australia. The gecko’s range edge spans the urban-woodland interface at the edge of urban areas. Across this edge, gecko abundance shows a steep decline, being lower in the woodland. Two parasite species (a mite, and a pentastome) are co-evolved with H.&nbsp;frenatus, and these species become less prevalent as the geckos become less abundant. A third species of parasite (another pentastome) is native to Australia and has no co-evolutionary history with H.&nbsp;frenatus. This species became more prevalent as the geckos become less abundant. These dramatic shifts in parasitism (occurring over 3.5 km) confirm that host-parasite dynamics can vary substantially across the range edge of this gecko host. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Parasite prevalence shifts dramatically across a range edge in geckos </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>pecies interactions can determine range limits, and parasitism is the most intimate of such interactions. Intriguingly, the very conditions on range edges likely change host-parasite dynamics in non-trivial ways. Range edges are often associated with clines in host density, and with environmental transitions, both of which may affect parasite transmission. On advancing range edges, founder events and fitness/dispersal costs of parasitism may also cause parasites to be lost on range edges. Here we examine the prevalence of three species of parasite across the range edge of an invasive gecko, <i>Hemidactylus frenatus</i>, in north-eastern Australia. The gecko’s range edge spans the urban-woodland interface at the edge of urban areas. Across this edge, gecko abundance shows a steep decline, being lower in the woodland. Two parasite species (a mite, and a pentastome) are co-evolved with <i>H.&nbsp;frenatus</i>, and these species become less prevalent as the geckos become less abundant. A third species of parasite (another pentastome) is native to Australia and has no co-evolutionary history with <i>H.&nbsp;frenatus</i>. This species became more prevalent as the geckos become less abundant. These dramatic shifts in parasitism (occurring over 3.5 km) confirm that host-parasite dynamics can vary substantially across the range edge of this gecko host. <a href="http://dx.doi.org/10.1086/689820">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT “Diversity and coevolutionary dynamics in high-dimensional phenotype spaces” http://amnat.org/an/newpapers/FebDoebeli.html Complex evolutionary dynamics during macroevolutionary community assembly Understanding grand patterns of life is a central goal of biological research, and large-scale, macroevolutionary patterns, such as mass extinctions, bursts of new diversity during adaptive radiations, or long-term changes in the speed of evolution, have fascinated evolutionary biologists for decades. Ultimately, macroevolutionary patterns are consequences of births and deaths of individual organisms, which cause changes in the genetic makeup of populations. For example, adaptive radiations occur because new ecological types of individuals arise that can coexist with already existing types. Generating links between microevolutionary processes such as competition and predation, which directly affect individual birth and death rates, and macroevolutionary patterns is a major problem in theoretical biology. In a new study in The&nbsp;American Naturalist, Michael Doebeli from the University of British Columbia in Vancouver and Iaroslav Ispolatov from the University of Santiago in Chile have used microevolutionary models based on competition for resources to study long-term dynamics of diversification and coevolution between species. These two authors have a longstanding interest in the problem of speciation and the evolution of diversity, and their previous work has shown that gradual evolutionary change in phenotypes (evolutionary dynamics) can be nonstationary and never-ending, and even chaotic when the number of phenotypic features (phenotypic dimensions) that affect ecological interactions between individuals is high. They have now extended these models to include the emergence of new species over long time spans, and they then studied the long-term evolutionary dynamics of emerging lineages. They found that long-term evolutionary dynamics tend to be fast and nonstationary for an intermediate level of diversity, but tend to stabilize as the evolving communities reach a saturation level of diversity. They also found that the amount of diversity present at the saturation level increases rapidly with the number of phenotypic dimensions. These results provide new perspectives on major macroevolutionary patterns such as adaptive radiation, long-term changes in the speed of evolution, and the evolution of diversity. For adaptive radiation, the results suggest that the rate of evolutionary change should decrease as the radiation unfolds, resulting in stasis once the saturation level is reached. If new phenotype dimensions evolve, e.g., through gene duplication, another bout of fast evolutionary dynamics followed by stasis can be expected, thus generating a pattern resembling punctuated equilibrium. Finally, diversity may saturate for a given dimension of phenotype space, but may not saturate over very long time scales as new phenotypic dimensions evolve, essentially resulting in open-ended evolution of diversity. Hopefully, these theoretical insights can help guide empirical research trying to understand large-scale patterns in the evolutionary tree of life. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Complex evolutionary dynamics during macroevolutionary community assembly </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;">U</span>nderstanding grand patterns of life is a central goal of biological research, and large-scale, macroevolutionary patterns, such as mass extinctions, bursts of new diversity during adaptive radiations, or long-term changes in the speed of evolution, have fascinated evolutionary biologists for decades. Ultimately, macroevolutionary patterns are consequences of births and deaths of individual organisms, which cause changes in the genetic makeup of populations. For example, adaptive radiations occur because new ecological types of individuals arise that can coexist with already existing types. </p><p>Generating links between microevolutionary processes such as competition and predation, which directly affect individual birth and death rates, and macroevolutionary patterns is a major problem in theoretical biology. In a new study in <i>The&nbsp;American Naturalist</i>, Michael Doebeli from the University of British Columbia in Vancouver and Iaroslav Ispolatov from the University of Santiago in Chile have used microevolutionary models based on competition for resources to study long-term dynamics of diversification and coevolution between species. </p><p>These two authors have a longstanding interest in the problem of speciation and the evolution of diversity, and their previous work has shown that gradual evolutionary change in phenotypes (evolutionary dynamics) can be nonstationary and never-ending, and even chaotic when the number of phenotypic features (phenotypic dimensions) that affect ecological interactions between individuals is high. They have now extended these models to include the emergence of new species over long time spans, and they then studied the long-term evolutionary dynamics of emerging lineages. They found that long-term evolutionary dynamics tend to be fast and nonstationary for an intermediate level of diversity, but tend to stabilize as the evolving communities reach a saturation level of diversity. They also found that the amount of diversity present at the saturation level increases rapidly with the number of phenotypic dimensions. </p><p>These results provide new perspectives on major macroevolutionary patterns such as adaptive radiation, long-term changes in the speed of evolution, and the evolution of diversity. For adaptive radiation, the results suggest that the rate of evolutionary change should decrease as the radiation unfolds, resulting in stasis once the saturation level is reached. If new phenotype dimensions evolve, e.g., through gene duplication, another bout of fast evolutionary dynamics followed by stasis can be expected, thus generating a pattern resembling punctuated equilibrium. Finally, diversity may saturate for a given dimension of phenotype space, but may not saturate over very long time scales as new phenotypic dimensions evolve, essentially resulting in open-ended evolution of diversity. Hopefully, these theoretical insights can help guide empirical research trying to understand large-scale patterns in the evolutionary tree of life. <a href="http://dx.doi.org/10.1086/689891">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT “Trait evolution in adaptive radiations: modelling and measuring interspecific competition on phylogenies” http://amnat.org/an/newpapers/FebClarke-A.html Modeling and measuring interspecific competition on phylogenetic trait data Abstract The incorporation of ecological processes into models of trait evolution is important for understanding past drivers of evolutionary change. Species interactions have long been thought to be key drivers of trait evolution. However, models for comparative data that account for interactions between species are lacking. One of the challenges is that such models are intractable and difficult to express analytically. Here we present phylogenetic models of trait evolution that include interspecific competition amongst chosen species. Competition is modelled as a tendency of sympatric species to evolve towards difference from one another, producing trait overdispersion and high phylogenetic signal. The model predicts elevated trait variance across species and a slowdown in evolutionary rate both across the clade and within each branch. The model also predicts a reduction in correlation between otherwise correlated traits. We use an Approximate Bayesian Computation (ABC) approach to estimate model parameters. We find reasonable power to detect competition in sufficiently large (20+ species) trees, compared with Brownian trait evolution and with OU and Early-Burst models. We apply the model to examine the evolution of bill morphology of Darwin’s finches, and find evidence that competition affects the evolution of bill length. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Modeling and measuring interspecific competition on phylogenetic trait data </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 incorporation of ecological processes into models of trait evolution is important for understanding past drivers of evolutionary change. Species interactions have long been thought to be key drivers of trait evolution. However, models for comparative data that account for interactions between species are lacking. One of the challenges is that such models are intractable and difficult to express analytically. Here we present phylogenetic models of trait evolution that include interspecific competition amongst chosen species. Competition is modelled as a tendency of sympatric species to evolve towards difference from one another, producing trait overdispersion and high phylogenetic signal. The model predicts elevated trait variance across species and a slowdown in evolutionary rate both across the clade and within each branch. The model also predicts a reduction in correlation between otherwise correlated traits. We use an Approximate Bayesian Computation (ABC) approach to estimate model parameters. We find reasonable power to detect competition in sufficiently large (20+ species) trees, compared with Brownian trait evolution and with OU and Early-Burst models. We apply the model to examine the evolution of bill morphology of Darwin’s finches, and find evidence that competition affects the evolution of bill length. <a href="http://dx.doi.org/10.1086/689819">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT “Rapid changes in the sex linkage of male coloration in introduced guppy populations” http://amnat.org/an/newpapers/FebGordon.html Not only body color, but also its sex linkage relationships evolves rapidly in guppies introduced to new environments Many animals have a pair of sex chromosomes, where in one of the sexes (the male in mammals and many fish) one of them tends to be smaller (the Y chromosome) and recombines less with its pair (the X chromosome). Some male-specific traits are found in the Y chromosome and can thus only be inherited by males, while others are found in other parts of the genome, and can therefore be inherited by females. In guppies, males show bright colorations while females are drab. Most of this coloration is solely Y-linked in populations that coexist with a diverse community of predators. However, this is not the case in populations with lower predation pressure and stronger sexual selection. In this study researchers Swanne Gordon (University of Jyväskylä), Andrés Lopez-Sepulcre (CNRS Paris), Diana Rumbo, and David Reznick (University of California, Riverside) investigate how fast these differences in sex-linkage among populations can evolve. They show in several experimental populations of rapidly evolving Trinidadian guppies (Poecilia reticulata) introduced from high to low predation environments that changes in the sex linkage of traits can also occur very fast in rapidly evolving populations. More specifically, body coloration changes from being linked to the non-recombining parts of the Y-chromosome to being mainly X- or autosomally-linked in as little as 20 years, and shows substantial changes already after just one year (or three generations). These results have important consequences for our understanding of sexual selection and rapid evolution, since different degrees of sex linkage can affect rates of evolution. Moreover, they give new insights into the origin and evolution of sex chromosomes, where the prevailing theory so far points to an overall loss, rather than gain, of recombination over time. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Not only body color, but also its sex linkage relationships evolves rapidly in guppies introduced to new environments </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;">M</span>any animals have a pair of sex chromosomes, where in one of the sexes (the male in mammals and many fish) one of them tends to be smaller (the Y chromosome) and recombines less with its pair (the X chromosome). Some male-specific traits are found in the Y chromosome and can thus only be inherited by males, while others are found in other parts of the genome, and can therefore be inherited by females. In guppies, males show bright colorations while females are drab. Most of this coloration is solely Y-linked in populations that coexist with a diverse community of predators. However, this is not the case in populations with lower predation pressure and stronger sexual selection. In this study researchers Swanne Gordon (University of Jyväskylä), Andrés Lopez-Sepulcre (CNRS Paris), Diana Rumbo, and David Reznick (University of California, Riverside) investigate how fast these differences in sex-linkage among populations can evolve. They show in several experimental populations of rapidly evolving Trinidadian guppies (<i>Poecilia reticulata</i>) introduced from high to low predation environments that changes in the sex linkage of traits can also occur very fast in rapidly evolving populations. More specifically, body coloration changes from being linked to the non-recombining parts of the Y-chromosome to being mainly X- or autosomally-linked in as little as 20 years, and shows substantial changes already after just one year (or three generations). These results have important consequences for our understanding of sexual selection and rapid evolution, since different degrees of sex linkage can affect rates of evolution. Moreover, they give new insights into the origin and evolution of sex chromosomes, where the prevailing theory so far points to an overall loss, rather than gain, of recombination over time. <a href="http://dx.doi.org/10.1086/689864">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT “Differential survival between visual environments supports a role of divergent sensory drive in cichlid fish speciation” http://amnat.org/an/newpapers/JanMaan.html Fitness consequences of visual adaptation: cichlid fish survive best in their natural light environment Animal sensory systems are highly diverse, as they must adapt to different sensory environments. A recent study shows that even in the laboratory, sensory conditions can have a major impact on fitness. Researchers from the Netherlands (University of Groningen) and Switzerland (Eawag Institute and University of Bern) investigate the causes and consequences of visual adaptation, and its possible role in species divergence. They collected two species of cichlid fish from Lake Victoria (East Africa), that inhabit different depth ranges with different light regimes: in deeper waters, blue light hardly penetrates and the light environment is dominated by green and yellow light. The two species differ in visual system properties, matching these different visual environments. To test whether the fish have indeed adapted to their environment, the researchers mimicked the shallow-water and deep-water light conditions in the laboratory and raised both species in both conditions. After one year, they found that both species survived significantly better in the light regime that mimicked their natural habitat. This confirms that the fish’ visual systems have indeed adapted to their natural light environment. For further confirmation, the researchers also bred hybrids between the two species. Consistent with previous observations on hybrids, these fish survived just as well as the parental species, but most importantly, their survival did not differ between light conditions. This implies that the light-dependent survival observed in the parental species is indeed due to genetic effects, presumably the genetically based differences in visual system properties. Together, these observations suggest that depth-mediated variation in light environments in Lake Victoria generates strong divergent selection on fish visual properties, strong enough to cause major differences in survival. The same mechanism probably works in other aquatic environments as well, because visual conditions under water can vary dramatically between geographic locations or depth ranges. The results of this study are also relevant for aquaculture: manipulating the light regime may improve fish performance and welfare. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Fitness consequences of visual adaptation: cichlid fish survive best in their natural light environment </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>nimal sensory systems are highly diverse, as they must adapt to different sensory environments. A recent study shows that even in the laboratory, sensory conditions can have a major impact on fitness. </p><p>Researchers from the Netherlands (University of Groningen) and Switzerland (Eawag Institute and University of Bern) investigate the causes and consequences of visual adaptation, and its possible role in species divergence. They collected two species of cichlid fish from Lake Victoria (East Africa), that inhabit different depth ranges with different light regimes: in deeper waters, blue light hardly penetrates and the light environment is dominated by green and yellow light. The two species differ in visual system properties, matching these different visual environments. </p><p>To test whether the fish have indeed adapted to their environment, the researchers mimicked the shallow-water and deep-water light conditions in the laboratory and raised both species in both conditions. After one year, they found that both species survived significantly better in the light regime that mimicked their natural habitat. This confirms that the fish’ visual systems have indeed adapted to their natural light environment. </p><p>For further confirmation, the researchers also bred hybrids between the two species. Consistent with previous observations on hybrids, these fish survived just as well as the parental species, but most importantly, their survival did not differ between light conditions. This implies that the light-dependent survival observed in the parental species is indeed due to genetic effects, presumably the genetically based differences in visual system properties. Together, these observations suggest that depth-mediated variation in light environments in Lake Victoria generates strong divergent selection on fish visual properties, strong enough to cause major differences in survival. </p><p>The same mechanism probably works in other aquatic environments as well, because visual conditions under water can vary dramatically between geographic locations or depth ranges. The results of this study are also relevant for aquaculture: manipulating the light regime may improve fish performance and welfare. <a href="http://dx.doi.org/10.1086/689605">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT “Predator-prey coevolution drives productivity-richness relationships in planktonic systems” http://amnat.org/an/newpapers/JanPu-A.html Abstract The relationship between environmental productivity and species richness often varies among empirical studies and, despite much research, simple explanations for this phenomenon remain elusive. We investigated how phytoplankton and zooplankton coevolution shapes productivity-richness relationships in both phytoplankton and zooplankton, using a simple nutrient-phytoplankton-zooplankton model that incorporates size-dependent metabolic rates summarized from empirical studies. The model allowed comparisons of evolved species richness across productivity levels and at different evolutionary times. Our results show that disruptive selection leads to evolutionary branching of phytoplankton and zooplankton. Both the time required for evolutionary branching and the number of evolved species in phytoplankton and zooplankton tend to increase with productivity, producing a transient unimodal or positive productivity-richness relationship but followed by a positive productivity-richness relationship for both groups over long enough evolutionary time. Our findings suggest that coevolution between phytoplankton and zooplankton can drive the two common forms (unimodal and positive) of productivity-richness relationships in nature. In Memoriam: Dr. Zhichao Pu We are saddened to report that Dr. Zhichao Pu (1983-2016), the first author of this article, passed away on Thursday, August 11, 2016 in a swimming accident. Dr. Pu received his B.S. from Fudan University (Shanghai, China) in 2006, and his Ph.D. from Georgia Institute of Technology in 2015. His research focused on community ecology, using both theoretical and experimental approaches. He has published 13 peer-reviewed articles (including this one). Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <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 relationship between environmental productivity and species richness often varies among empirical studies and, despite much research, simple explanations for this phenomenon remain elusive. We investigated how phytoplankton and zooplankton coevolution shapes productivity-richness relationships in both phytoplankton and zooplankton, using a simple nutrient-phytoplankton-zooplankton model that incorporates size-dependent metabolic rates summarized from empirical studies. The model allowed comparisons of evolved species richness across productivity levels and at different evolutionary times. Our results show that disruptive selection leads to evolutionary branching of phytoplankton and zooplankton. Both the time required for evolutionary branching and the number of evolved species in phytoplankton and zooplankton tend to increase with productivity, producing a transient unimodal or positive productivity-richness relationship but followed by a positive productivity-richness relationship for both groups over long enough evolutionary time. Our findings suggest that coevolution between phytoplankton and zooplankton can drive the two common forms (unimodal and positive) of productivity-richness relationships in nature.</p> <h3>In Memoriam: Dr. Zhichao Pu</h3> <p>We are saddened to report that Dr. Zhichao Pu (1983-2016), the first author of this article, passed away on Thursday, August 11, 2016 in a swimming accident. Dr. Pu received his B.S. from Fudan University (Shanghai, China) in 2006, and his Ph.D. from Georgia Institute of Technology in 2015. His research focused on community ecology, using both theoretical and experimental approaches. He has published 13 peer-reviewed articles (including this one). <a href="http://dx.doi.org/10.1086/689550">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT “Shaping the latitudinal diversity gradient: New perspectives from a synthesis of paleobiology and biogeography” http://amnat.org/an/newpapers/JanJablonski.html The factors shaping the world’s latitudinal diversity gradient, the dramatic rise in diversity from poles to equator, have been debated for 150 years. A synthesis of both fossil and present-day data on a major component of the marine biota shows that the diversity gradient must involve mutually reinforcing causes – a perfect storm – rather than a single mechanism. By analyzing the past and present distribution of species and evolutionary lineages of marine bivalves – scallops, mussels, cockles, and their kin, known for their exceptionally rich fossil record – the researchers find that the strong diversity trend of this group cannot be explained solely by the factors like climate or nutrients within each specific region, or by the movement of species into and out of those regions. Both effects, often cast as alternatives, must be operating. A strong role for local effects is seen in the patterns of diversity loss over the past 3 million years, with once-rich fossil faunas declining in direct proportion to the size of the temperature drop experienced by each region as ice ages set in. On the other hand, the fossil record shows that bivalve lineages tend to start in the tropics and spread to higher latitudes while retaining their tropical presence, expanding across temperature lines and so contradicting an exclusive role for local conditions. With both the youngest and oldest lineages found in the tropics, this finding challenges another pair of supposed alternatives, often phrased as the question, are the tropics a cradle or museum of biodiversity? Comparing diversity patterns among, rather than along, coastlines also shows that the expansion of lineages helps shape latitudinal diversity trends. In their global database of 62,000 records of living marine bivalve species, the researchers find that temperate southeast Australia and southeast Japan each contains more species than the entire tropical Caribbean region. This result was unexpected, because the Caribbean is 10 times larger, much warmer and less seasonal, and contains a much wider array of habitats including coral reefs. Poleward “spillover” of species from the massively diverse tropical west Pacific into the adjacent temperate zones evidently explains their remarkably high diversities, an out-of-the-tropics dynamic that overwhelms expectations drawn from a single coastline. Taken together, the evidence shows that the global latitudinal gradient is shaped both by local effects and by the long-term expansions of geographic ranges – neither explanation alone is sufficient. Many of the biggest biological patterns today and in the history of life may be such “perfect storms,” where mutually reinforcing processes generate the most extreme outcomes. Other candidates for perfect storms include the “Coral Triangle” diversity peak in the today’s oceans, the Cambrian Explosion of multicellular life 530 million years ago, the greatest mass extinction in the history of life 250 million years ago, and the explosive diversifications of flowering plants and insects over the past 100 million years. The research team cuts across academic generations: lead author David Jablonski, now at the University of Chicago, was a postdoctoral fellow with James Valentine, now at the University of California, Berkeley; Kaustuv Roy, now at the University of California, San Diego, was Jablonski’s PhD student and then a postdoc with Jablonski and Valentine; and Shan Huang, now at the Senckenberg Biodiversity & Climate Research Center in Frankfurt, Germany, was a postdoc with Jablonski, Valentine, and Roy. Read&nbsp;the&nbsp;Article 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;">T</span>he factors shaping the world’s latitudinal diversity gradient, the dramatic rise in diversity from poles to equator, have been debated for 150 years. A synthesis of both fossil and present-day data on a major component of the marine biota shows that the diversity gradient must involve mutually reinforcing causes – a perfect storm – rather than a single mechanism. </p><p>By analyzing the past and present distribution of species and evolutionary lineages of marine bivalves – scallops, mussels, cockles, and their kin, known for their exceptionally rich fossil record – the researchers find that the strong diversity trend of this group cannot be explained solely by the factors like climate or nutrients within each specific region, or by the movement of species into and out of those regions. Both effects, often cast as alternatives, must be operating. </p><p>A strong role for local effects is seen in the patterns of diversity loss over the past 3 million years, with once-rich fossil faunas declining in direct proportion to the size of the temperature drop experienced by each region as ice ages set in. On the other hand, the fossil record shows that bivalve lineages tend to start in the tropics and spread to higher latitudes while retaining their tropical presence, expanding across temperature lines and so contradicting an exclusive role for local conditions. With both the youngest and oldest lineages found in the tropics, this finding challenges another pair of supposed alternatives, often phrased as the question, are the tropics a cradle or museum of biodiversity? </p><p>Comparing diversity patterns among, rather than along, coastlines also shows that the expansion of lineages helps shape latitudinal diversity trends. In their global database of 62,000 records of living marine bivalve species, the researchers find that temperate southeast Australia and southeast Japan each contains more species than the entire tropical Caribbean region. This result was unexpected, because the Caribbean is 10 times larger, much warmer and less seasonal, and contains a much wider array of habitats including coral reefs. Poleward “spillover” of species from the massively diverse tropical west Pacific into the adjacent temperate zones evidently explains their remarkably high diversities, an out-of-the-tropics dynamic that overwhelms expectations drawn from a single coastline. </p><p>Taken together, the evidence shows that the global latitudinal gradient is shaped both by local effects and by the long-term expansions of geographic ranges – neither explanation alone is sufficient. Many of the biggest biological patterns today and in the history of life may be such “perfect storms,” where mutually reinforcing processes generate the most extreme outcomes. Other candidates for perfect storms include the “Coral Triangle” diversity peak in the today’s oceans, the Cambrian Explosion of multicellular life 530 million years ago, the greatest mass extinction in the history of life 250 million years ago, and the explosive diversifications of flowering plants and insects over the past 100 million years. </p><p>The research team cuts across academic generations: lead author David Jablonski, now at the University of Chicago, was a postdoctoral fellow with James Valentine, now at the University of California, Berkeley; Kaustuv Roy, now at the University of California, San Diego, was Jablonski’s PhD student and then a postdoc with Jablonski and Valentine; and Shan Huang, now at the Senckenberg Biodiversity & Climate Research Center in Frankfurt, Germany, was a postdoc with Jablonski, Valentine, and Roy. <a href="http://dx.doi.org/10.1086/689739">Read&nbsp;the&nbsp;Article</a> </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, 09 Dec 2016 06:00:00 GMT