ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Sat, 19 Jan 2019 06:00:00 GMT 60 “Nighttime ecology: the ‘nocturnal problem’ revisited” https://amnat.org/an/newpapers/AprGaston-A.html The DOI will be https://dx.doi.org/10.1086/702250 Abstract The existence of a synthetic program of research on what was then termed ‘the nocturnal problem’, and which we might now call ‘nighttime ecology’, was declared more than 70 years ago. In reality this failed to materialize, arguably as a consequence of practical challenges in studying organisms at night and concentration instead on the existence of circadian rhythms, the mechanisms that give rise to them, and their consequences. This legacy is evident to this day, with consideration of the ecology of the nighttime markedly underrepresented in ecological research and literature. However, several factors suggest that it would be timely to revive the vision of a comprehensive research program in nighttime ecology. These include (i) that study of the ecology of the night is being revolutionized by new and improved technologies,; (ii) suggestions that far from being a minor component of biodiversity a high proportion of animal species are active at night; (iii) that fundamental questions remain largely unanswered as to differences and connections between the ecology of the daytime and nighttime; and (iv) that the nighttime environment is coming under severe anthropogenic pressure. In this article, I seek to re-establish ‘nighttime ecology’ as a synthetic program of research, highlighting key focal topics, key questions, and providing an overview of the current state of understanding and developments. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702250 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702250">Read the Article</a></i> </p> --><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he existence of a synthetic program of research on what was then termed ‘the nocturnal problem’, and which we might now call ‘nighttime ecology’, was declared more than 70 years ago. In reality this failed to materialize, arguably as a consequence of practical challenges in studying organisms at night and concentration instead on the existence of circadian rhythms, the mechanisms that give rise to them, and their consequences. This legacy is evident to this day, with consideration of the ecology of the nighttime markedly underrepresented in ecological research and literature. However, several factors suggest that it would be timely to revive the vision of a comprehensive research program in nighttime ecology. These include (i) that study of the ecology of the night is being revolutionized by new and improved technologies,; (ii) suggestions that far from being a minor component of biodiversity a high proportion of animal species are active at night; (iii) that fundamental questions remain largely unanswered as to differences and connections between the ecology of the daytime and nighttime; and (iv) that the nighttime environment is coming under severe anthropogenic pressure. In this article, I seek to re-establish ‘nighttime ecology’ as a synthetic program of research, highlighting key focal topics, key questions, and providing an overview of the current state of understanding and developments. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Jan 2019 06:00:00 GMT “Heterogeneous matrix habitat drives species occurrences in complex, fragmented landscapes” https://amnat.org/an/newpapers/MayBrodie-A.html The DOI will be https://dx.doi.org/10.1086/702589 Abstract A&nbsp;fundamental tenet of modern ecology and conservation science is that species occurrence in habitat patches can be determined by patch area and isolation. But such island biogeographic models often poorly predict actual species occurrences in structurally complex landscapes that typify most ecosystems. Recent advances in circuit theory have enhanced estimates of species dispersal, and through integration with island biogeography, can provide powerful ways to predict landscape-scale distribution of species assemblages. Applying such an integrative analytical framework to 43 bird species in Tanzania improved model fit by an average of 2.2-fold over models where patch isolation was estimated without accounting for landscape matrix heterogeneity. This approach also allowed us to assess species-specific dispersal rates and quantify differences among land cover types in their permeability to animal movement. These results reaffirm the utility of foundational island biogeographic principles, yet with an important caveat. Two-thirds of the variance in species occurrence in habitat fragments can be explained simply by patch area and isolation, conditional on isolation explicitly accounting for the spatial configuration of different land cover types in the landscape matrix. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702589 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702589">Read the Article</a></i> </p> --><h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>&nbsp;fundamental tenet of modern ecology and conservation science is that species occurrence in habitat patches can be determined by patch area and isolation. But such island biogeographic models often poorly predict actual species occurrences in structurally complex landscapes that typify most ecosystems. Recent advances in circuit theory have enhanced estimates of species dispersal, and through integration with island biogeography, can provide powerful ways to predict landscape-scale distribution of species assemblages. Applying such an integrative analytical framework to 43 bird species in Tanzania improved model fit by an average of 2.2-fold over models where patch isolation was estimated without accounting for landscape matrix heterogeneity. This approach also allowed us to assess species-specific dispersal rates and quantify differences among land cover types in their permeability to animal movement. These results reaffirm the utility of foundational island biogeographic principles, yet with an important caveat. Two-thirds of the variance in species occurrence in habitat fragments can be explained simply by patch area and isolation, conditional on isolation explicitly accounting for the spatial configuration of different land cover types in the landscape matrix.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Jan 2019 06:00:00 GMT “Prey responses to exotic predators: effects of old risks and new cues” https://amnat.org/an/newpapers/AprEhlman.html The DOI will be https://dx.doi.org/10.1086/702252 New theory on prey responses to exotic predators offers insights and surprises Behavioral ecological theory on the interactions of predators and prey commonly assumes that predators and prey have coevolved to respond appropriately to one another. Increasingly in the modern world, however, prey must face exotic, invasive predators to which they are not well-adapted. This work develops a predictive, cue-based theory of prey responses to exotic predators. The authors ask how differences in preys’ evolutionary histories with native predators might explain variation in their success with exotic predators: Does the degree of similarity between native and non-native predator cues affect prey responses? Usually. Does the frequency of predation in a prey’s past affect responses to exotic predators? A bit, but sometimes in the opposite direction of previous work. Does the degree to which prey generalize among predator types affect their perception of risk with exotic predators? Yes, in some interesting ways. For empiricists working towards understanding variation in prey responses to exotic predators, this theory offers insights and testable predictions. Abstract Exotic predators can have major negative impacts on prey. Importantly, prey vary considerably in their behavioral responses to exotic predators. Factors proposed to explain variation in prey response to exotic predators include the similarity of new predators to familiar, native predators, the prevalence and diversity of predators in a prey’s past, and variation in a prey’s innate ability to discriminate between predators and safety. While these factors have been put forth verbally in the literature, no theory exists that combines these hypotheses in a common conceptual framework using a unified behavioral model. Here, we formalize existing verbal arguments by modeling variation in prey responses to new predators in a state-dependent detection theory (SDDT) framework. We find that while some conventional wisdom is upheld, novel predictions emerge. As expected, prey respond poorly to exotic predators that do not closely resemble familiar predators. Furthermore, a history with more abundant or diverse native predators can lessen effects of some exotic predators on prey; however, under some conditions, the opposite prediction emerges. Also, prey that evolved in situations where they easily discriminate between safe and dangerous situations can be more susceptible to novel predators. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702252 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702252">Read the Article</a></i> </p> --> <p><b>New theory on prey responses to exotic predators offers insights and surprises </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>ehavioral ecological theory on the interactions of predators and prey commonly assumes that predators and prey have coevolved to respond appropriately to one another. Increasingly in the modern world, however, prey must face exotic, invasive predators to which they are not well-adapted. This work develops a predictive, cue-based theory of prey responses to exotic predators. The authors ask how differences in preys’ evolutionary histories with native predators might explain variation in their success with exotic predators: Does the degree of similarity between native and non-native predator cues affect prey responses? Usually. Does the frequency of predation in a prey’s past affect responses to exotic predators? A bit, but sometimes in the opposite direction of previous work. Does the degree to which prey generalize among predator types affect their perception of risk with exotic predators? Yes, in some interesting ways. For empiricists working towards understanding variation in prey responses to exotic predators, this theory offers insights and testable predictions. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>xotic predators can have major negative impacts on prey. Importantly, prey vary considerably in their behavioral responses to exotic predators. Factors proposed to explain variation in prey response to exotic predators include the similarity of new predators to familiar, native predators, the prevalence and diversity of predators in a prey’s past, and variation in a prey’s innate ability to discriminate between predators and safety. While these factors have been put forth verbally in the literature, no theory exists that combines these hypotheses in a common conceptual framework using a unified behavioral model. Here, we formalize existing verbal arguments by modeling variation in prey responses to new predators in a state-dependent detection theory (SDDT) framework. We find that while some conventional wisdom is upheld, novel predictions emerge. As expected, prey respond poorly to exotic predators that do not closely resemble familiar predators. Furthermore, a history with more abundant or diverse native predators can lessen effects of some exotic predators on prey; however, under some conditions, the opposite prediction emerges. Also, prey that evolved in situations where they easily discriminate between safe and dangerous situations can be more susceptible to novel predators. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Jan 2019 06:00:00 GMT “Age-specific offspring mortality economically tracks food abundance in a piscivorous seabird” https://amnat.org/an/newpapers/AprVedder.html The DOI will be https://dx.doi.org/10.1086/702304 Earlier chick mortality with low food availability reduces the energy wasted on non-fledged chicks in poor years Why does mortality peak at the start of life? One idea is that this early mortality reduces the amount of resources wasted on unsuccessful offspring, and is the result of a strategy adopted by the parents that is beneficial when unpredictable foraging conditions turn out bad. By analysing a 24-year dataset of age-specific chick mortality of common terns (fish-eating seabirds), an international team of researchers has found that with reduced food availability, fledgling success decreased in an economical fashion. When herring (the terns’ main food source) were rare, chick mortality increased, but because chicks died earlier, this did not lead to a proportional increase in energy wasted on non-fledged chicks. Disadvantaged, last-hatching, chicks were particularly cheap when they died, but, per hatchling, the chicks without siblings required the least waste of energy. The researchers suggest that parents may facilitate early mortality of excess offspring by promoting competitive asymmetries among offspring from the start, but that competition between siblings may interfere with the parents’ best interests despite such asymmetries. These results thereby support evolutionary theory on age-specific mortality, parental effects, sibling competition, and parent-offspring-conflict. The researchers conclude, “Despite it being an extremely sad sight to see so many small chicks die when there is little food, this may be nature’s way of ensuring that the parents survive and are able to reproduce in future years when food may be more abundant.” Abstract Earlier offspring mortality prior to independence saves resources for kin, which should be more beneficial when food is short. Using 24 years of data on age-specific common tern (Sterna hirundo) chick mortality, best described by the Gompertz function, and estimates of energy consumption per age of mortality, we investigated how energy wasted on non-fledged chicks depends on brood size, hatching order and annual abundance of herring (Clupea harengus), the main food source. We found mortality directly after hatching (Gompertz baseline mortality) to be high and to increase with decreasing herring abundance. Mortality declined with age, at a rate relatively insensitive to herring abundance. The sensitivity of baseline mortality to herring abundance reduced energy wasted on non-fledged chicks when herring was short. Among chicks that did not fledge, last-hatched chicks were less costly than earlier hatched chicks, due to their earlier mortality. However, per hatchling produced, the least energy was wasted on chicks without siblings, due to their baseline mortality being most sensitive to herring abundance. We suggest that earlier mortality of offspring when food is short facilitates economic adjustment of post-hatching parental investment to food abundance, but that such economic brood reduction may be constrained by sibling competition. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702304 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702304">Read the Article</a></i> </p> --> <p><b>Earlier chick mortality with low food availability reduces the energy wasted on non-fledged chicks in poor years </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hy does mortality peak at the start of life? One idea is that this early mortality reduces the amount of resources wasted on unsuccessful offspring, and is the result of a strategy adopted by the parents that is beneficial when unpredictable foraging conditions turn out bad. By analysing a 24-year dataset of age-specific chick mortality of common terns (fish-eating seabirds), an international team of researchers has found that with reduced food availability, fledgling success decreased in an economical fashion. When herring (the terns’ main food source) were rare, chick mortality increased, but because chicks died earlier, this did not lead to a proportional increase in energy wasted on non-fledged chicks. Disadvantaged, last-hatching, chicks were particularly cheap when they died, but, per hatchling, the chicks without siblings required the least waste of energy. The researchers suggest that parents may facilitate early mortality of excess offspring by promoting competitive asymmetries among offspring from the start, but that competition between siblings may interfere with the parents’ best interests despite such asymmetries. These results thereby support evolutionary theory on age-specific mortality, parental effects, sibling competition, and parent-offspring-conflict. The researchers conclude, “Despite it being an extremely sad sight to see so many small chicks die when there is little food, this may be nature’s way of ensuring that the parents survive and are able to reproduce in future years when food may be more abundant.”</p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>arlier offspring mortality prior to independence saves resources for kin, which should be more beneficial when food is short. Using 24 years of data on age-specific common tern (<i>Sterna hirundo</i>) chick mortality, best described by the Gompertz function, and estimates of energy consumption per age of mortality, we investigated how energy wasted on non-fledged chicks depends on brood size, hatching order and annual abundance of herring (<i>Clupea harengus</i>), the main food source. We found mortality directly after hatching (Gompertz baseline mortality) to be high and to increase with decreasing herring abundance. Mortality declined with age, at a rate relatively insensitive to herring abundance. The sensitivity of baseline mortality to herring abundance reduced energy wasted on non-fledged chicks when herring was short. Among chicks that did not fledge, last-hatched chicks were less costly than earlier hatched chicks, due to their earlier mortality. However, per hatchling produced, the least energy was wasted on chicks without siblings, due to their baseline mortality being most sensitive to herring abundance. We suggest that earlier mortality of offspring when food is short facilitates economic adjustment of post-hatching parental investment to food abundance, but that such economic brood reduction may be constrained by sibling competition. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Jan 2019 06:00:00 GMT “Evolution of the two sexes under internal fertilization and alternative evolutionary pathways” https://amnat.org/an/newpapers/MayLehtonen.html The DOI will be https://dx.doi.org/10.1086/702588 Anisogamy theory is robust under internal fertilization and sperm packets, bridging gap between theory and empirical tests Biologically, the two sexes are defined by the size of their gametes. Females are by definition the type that produces the larger gametes (e.g. eggs) and males the type that produces the smaller gametes (e.g. sperm). In this sense the origin of gamete size dimorphism is synonymous with the origin of the two sexes. Our understanding of this major event in evolutionary history is largely based on so-called gamete dynamics theory, where there are simultaneous selective pressures driving selection for numerous (hence small) and large (hence less numerous) gametes. Small and numerous gametes are good at gaining fertilizations, while large gametes are good at provisioning offspring. Although empirical evidence is fairly supportive of this theory, much of the evidence comes from organisms with simple forms of internal fertilization, while the original theory is derived for external fertilizers. Furthermore, some of these organisms divide their gametes into ‘sperm packets’, further increasing the divide between theory and data. In a new article, Jussi Lehtonen of the University of Sydney, Australia, and Geoff Parker of the University of Liverpool, UK, generalize previous theory on the origin of the two sexes, showing that the theory works equally well under the biology of these model organisms. Hence gamete dynamics theory represents a potent rationale for the origin of the two sexes. Abstract Transition from isogamy to anisogamy, hence males and females, leads to sexual selection, sexual conflict, sexual dimorphism, and sex roles. Gamete dynamics theory links biophysics of gamete limitation, gamete competition and resource requirements for zygote survival, and assumes broadcast spawning. It makes testable predictions, but most comparative tests use volvocine algae, which feature internal fertilization. We broaden this theory by comparing broadcast spawning predictions with two plausible internal fertilization scenarios: gamete-casting/brooding (one mating type retains gametes internally, the other broadcasts them) and packet-casting/brooding (one type retains gametes internally, the other broadcasts packets containing gametes, which are released for fertilization). Models show that predictions are remarkably robust to these radical changes, yielding (i) isogamy under low gamete limitation, low gamete competition, and similar required resources for gametes and zygotes, (ii) anisogamy when gamete competition and/or limitation are higher, and when zygotes require more resources than gametes, as is likely as multicellularity develops, (iii) a positive correlation between multicellular complexity and anisogamy ratio, and (iv) under gamete competition, only brooders becoming female. Thus gamete dynamics theory represents a potent rationale for isogamy/anisogamy, and makes similar testable predictions for broadcast spawners and internal fertilizers, regardless of whether anisogamy or internal fertilization evolved first. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702588 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702588">Read the Article</a></i> </p> --> <p><b>Anisogamy theory is robust under internal fertilization and sperm packets, bridging gap between theory and empirical tests </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>iologically, the two sexes are defined by the size of their gametes. Females are by definition the type that produces the larger gametes (e.g. eggs) and males the type that produces the smaller gametes (e.g. sperm). In this sense the origin of gamete size dimorphism is synonymous with the origin of the two sexes. Our understanding of this major event in evolutionary history is largely based on so-called gamete dynamics theory, where there are simultaneous selective pressures driving selection for numerous (hence small) and large (hence less numerous) gametes. Small and numerous gametes are good at gaining fertilizations, while large gametes are good at provisioning offspring. Although empirical evidence is fairly supportive of this theory, much of the evidence comes from organisms with simple forms of internal fertilization, while the original theory is derived for external fertilizers. Furthermore, some of these organisms divide their gametes into ‘sperm packets’, further increasing the divide between theory and data. In a new article, Jussi Lehtonen of the University of Sydney, Australia, and Geoff Parker of the University of Liverpool, UK, generalize previous theory on the origin of the two sexes, showing that the theory works equally well under the biology of these model organisms. Hence gamete dynamics theory represents a potent rationale for the origin of the two sexes. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>ransition from isogamy to anisogamy, hence males and females, leads to sexual selection, sexual conflict, sexual dimorphism, and sex roles. Gamete dynamics theory links biophysics of gamete limitation, gamete competition and resource requirements for zygote survival, and assumes broadcast spawning. It makes testable predictions, but most comparative tests use volvocine algae, which feature internal fertilization. We broaden this theory by comparing broadcast spawning predictions with two plausible internal fertilization scenarios: gamete-casting/brooding (one mating type retains gametes internally, the other broadcasts them) and packet-casting/brooding (one type retains gametes internally, the other broadcasts packets containing gametes, which are released for fertilization). Models show that predictions are remarkably robust to these radical changes, yielding (i) isogamy under low gamete limitation, low gamete competition, and similar required resources for gametes and zygotes, (ii) anisogamy when gamete competition and/or limitation are higher, and when zygotes require more resources than gametes, as is likely as multicellularity develops, (iii) a positive correlation between multicellular complexity and anisogamy ratio, and (iv) under gamete competition, only brooders becoming female. Thus gamete dynamics theory represents a potent rationale for isogamy/anisogamy, and makes similar testable predictions for broadcast spawners and internal fertilizers, regardless of whether anisogamy or internal fertilization evolved first.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Jan 2019 06:00:00 GMT “Mate choice vs. mate preference: inferences about color assortative mating differ between field and lab assays of poison frog behavior” https://amnat.org/an/newpapers/AprYang-A.html The DOI will be https://dx.doi.org/10.1086/702249 Choice vs. preference: patterns of color assortative mating differ between field and lab assays of poison frog behavior Abstract Co-divergence of mating traits and mate preferences can lead to behavioral isolation among lineages in early stages of speciation. However, mate preferences only limit gene flow when expressed as mate choice, and numerous factors might be more important than preferences in nature. In the extremely color polytypic strawberry poison frog (Oophaga pumilio), female mate preferences have co-diverged with color in most allopatric populations tested. Whether these lab-assayed preferences predict mating (gene flow) in the wild remains unclear. We observed courting pairs in a natural contact zone between red and blue lineages until oviposition or courtship termination. We found color-assortative mating in a disturbed habitat with high population density, but not in a secondary forest with lower density. Our results suggest color-assortative O.&nbsp;pumilio mate choice in the wild, but also mating patterns that do not match those predicted by lab-assayed preferences. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702249 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702249">Read the Article</a></i> </p> --> <p><b>Choice vs. preference: patterns of color assortative mating differ between field and lab assays of poison frog behavior </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>o-divergence of mating traits and mate preferences can lead to behavioral isolation among lineages in early stages of speciation. However, mate preferences only limit gene flow when expressed as mate choice, and numerous factors might be more important than preferences in nature. In the extremely color polytypic strawberry poison frog (<i>Oophaga pumilio</i>), female mate preferences have co-diverged with color in most allopatric populations tested. Whether these lab-assayed preferences predict mating (gene flow) in the wild remains unclear. We observed courting pairs in a natural contact zone between red and blue lineages until oviposition or courtship termination. We found color-assortative mating in a disturbed habitat with high population density, but not in a secondary forest with lower density. Our results suggest color-assortative <i>O.&nbsp;pumilio</i> mate choice in the wild, but also mating patterns that do not match those predicted by lab-assayed preferences. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Jan 2019 06:00:00 GMT “A vector-based approach to measure nutritional trade-offs within and between species” https://amnat.org/an/newpapers/JuneMorimoto.html The DOI will be https://dx.doi.org/10.1086/701898 A generalized approach to compare fitness landscapes within and between species in multi-dimensional data In Ancient Greece, somewhere around the year 300 BC, Euclid published his book Elements containing a single framework based on rigorous mathematical proof for Geometry. Little could he predict the far-reaching implications of his work. Some 22 centuries later, his life’s legacy was used to inspire biologists into creating a new framework – known as ‘nutritional geometry’, which is now widely used to investigate how animals and humans (should) eat. But how can one tell a good diet from a bad diet? And is there a universal ‘good diet recipe’ that solve all our problems? To answer these questions, scientists need to measure the effects of different diets on morphological and physiological traits, and quantify how these diets affect these traits in relation to others in the same individual, species, or between species. To date, however, there were no quantitative framework that allowed intra- and inter-specific comparisons of these effects. Building on previous attempts from colleagues, Morimoto and Lihoreau came up with a solution for this conundrum. They used the mathematical concept of vectors to quantify how much of each nutrient in the diet animals should eat to maximize a trait. Then, using fancy statistics that includes machine learning, they developed a model that could quantify differences in nutrient intake required to maximize traits within and across species. This work provides a significant advance in how we tell good from bad diets. The method of Morimoto and Lihoreau has the potential to be broadly used in ecology and evolution to understand the fundamentals of animal nutrition, but also their far-reaching consequences such as how individuals interact within societies, how species coexist and co-evolve in communities. The work can also be used in conservation and medical research to gain insights into what a healthy diet means for a given species (including us humans), and how to achieve it. Many centuries later, Euclid’s fundamental mathematical legacy becomes an evidence to explain the evolution of species, the onset of diseases, and possibly, the secret for a healthy life. Abstract Animals make feeding decisions to simultaneously maximize fitness traits that often require different nutrients. Recent quantitative methods have been developed to characterize these nutritional trade-offs from performance landscapes on which traits are mapped on a nutrient space defined by two nutrients. This limitation constrains the broad applications of previous methods to more complex data, and a generalized framework is needed. Here, we build upon previous methods and introduce a generalized vector-based approach – the Vector of Position approach – to study nutritional trade-offs in complex multi-dimensional spaces. The Vector of Position Approach allows the estimate of performance variations across entire landscapes (peaks and valleys), and comparison of these variations between animals. Using landmark published datasets on lifespan and reproduction landscapes, we illustrate how our approach gives accurate quantifications of nutritional trade-offs in two- and three-dimensional spaces, and can bring new insights into the underlying nutritional differences in trait expression between species. The Vector of Position Approach provides a generalized framework for investigating nutritional differences in life-history traits expression within and between species, an essential step for the development of comparative research on the evolution of animal nutritional strategies. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701898 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701898">Read the Article</a></i> </p> --> <p><b>A generalized approach to compare fitness landscapes within and between species in multi-dimensional data </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n Ancient Greece, somewhere around the year 300 BC, Euclid published his book Elements containing a single framework based on rigorous mathematical proof for Geometry. Little could he predict the far-reaching implications of his work. Some 22 centuries later, his life’s legacy was used to inspire biologists into creating a new framework – known as ‘nutritional geometry’, which is now widely used to investigate how animals and humans (should) eat. But how can one tell a good diet from a bad diet? And is there a universal ‘good diet recipe’ that solve all our problems? </p><p>To answer these questions, scientists need to measure the effects of different diets on morphological and physiological traits, and quantify how these diets affect these traits in relation to others in the same individual, species, or between species. To date, however, there were no quantitative framework that allowed intra- and inter-specific comparisons of these effects. </p><p>Building on previous attempts from colleagues, Morimoto and Lihoreau came up with a solution for this conundrum. They used the mathematical concept of vectors to quantify how much of each nutrient in the diet animals should eat to maximize a trait. Then, using fancy statistics that includes machine learning, they developed a model that could quantify differences in nutrient intake required to maximize traits within and across species. </p><p>This work provides a significant advance in how we tell good from bad diets. The method of Morimoto and Lihoreau has the potential to be broadly used in ecology and evolution to understand the fundamentals of animal nutrition, but also their far-reaching consequences such as how individuals interact within societies, how species coexist and co-evolve in communities. The work can also be used in conservation and medical research to gain insights into what a healthy diet means for a given species (including us humans), and how to achieve it. Many centuries later, Euclid’s fundamental mathematical legacy becomes an evidence to explain the evolution of species, the onset of diseases, and possibly, the secret for a healthy life. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>nimals make feeding decisions to simultaneously maximize fitness traits that often require different nutrients. Recent quantitative methods have been developed to characterize these nutritional trade-offs from performance landscapes on which traits are mapped on a nutrient space defined by two nutrients. This limitation constrains the broad applications of previous methods to more complex data, and a generalized framework is needed. Here, we build upon previous methods and introduce a generalized vector-based approach – the Vector of Position approach – to study nutritional trade-offs in complex multi-dimensional spaces. The Vector of Position Approach allows the estimate of performance variations across entire landscapes (peaks and valleys), and comparison of these variations between animals. Using landmark published datasets on lifespan and reproduction landscapes, we illustrate how our approach gives accurate quantifications of nutritional trade-offs in two- and three-dimensional spaces, and can bring new insights into the underlying nutritional differences in trait expression between species. The Vector of Position Approach provides a generalized framework for investigating nutritional differences in life-history traits expression within and between species, an essential step for the development of comparative research on the evolution of animal nutritional strategies. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 11 Jan 2019 06:00:00 GMT “Morphological polymorphism associated with alternative reproductive tactics in a plethodontid salamander” https://amnat.org/an/newpapers/AprPierson.html The DOI will be https://dx.doi.org/10.1086/702251 Pierson et al. describe alternative reproductive tactics and morphologies in a plethodontid salamander In populations of many organisms, several discrete reproductive tactics (called “alternative reproductive tactics” or “ARTs”) coexist. Often, these divergent tactics can be identified by different morphologies. The lungless salamanders (Family Plethodontidae) are a diverse group of amphibians with a center of diversity in the Appalachian Mountains of North America. Prior to the external transfer of a spermatophore, most male plethodontid salamanders court females through the performance of a ritualized “dance” and the delivery of complex reproductive pheromones. While these behaviors are variable among species, they are typically conserved within species. In this paper, Todd W. Pierson (University of Tennessee Knoxville), Jennifer Deitloff (Lock&nbsp;Haven University), Stanley K. Sessions (Hartwick College), Kenneth H. Kozak (University of Minnesota), and Benjamin M. Fitzpatrick (University of Tennessee Knoxville) use a combination of genetic, behavioral, and field observational data to describe an example of alternative reproductive tactics in a group of plethodontid salamanders—the two-lined salamander (Eurycea bislineata) species complex. “Searching” males have morphological traits and behaviors suited for locating and courting females in terrestrial habitats, while “guarding” males have morphological traits and behaviors suited for guarding females at aquatic nesting sites. Pierson et al. demonstrate that these two forms coexist in three putative species in the E.&nbsp;bislineata species complex, while other species in the group have only form or the other. The authors also demonstrate that these alternative reproductive tactics have divergent reproductive phenologies, describe the potential implications for parental care, and highlight directions for future research on this system. Abstract Understanding polymorphism is a central problem in evolution and ecology, and alternative reproductive tactics (ARTs) provide compelling examples for studying the origin and maintenance of behavioral and morphological variation. Much attention has been given to examples where “parasitic” individuals exploit the reproductive investment of “bourgeois” individuals, but some ARTs are instead maintained by environmental heterogeneity, with alternative tactics exhibiting differential fitness in discontinuous reproductive niches. We use genomic, behavioral, karyological, and field observational data to demonstrate one such example in plethodontid salamanders. These ARTs (“searching” and “guarding” males) are associated with different reproductive niches and, unlike most other examples in amphibians, demonstrate substantial morphological differences and inflexibility within a reproductive season. Evidence suggests the existence of these ARTs within three putative species in the two-lined salamander (Eurycea bislineata) species complex, with other members of this clade fixed for one of the two tactics. We highlight directions for future research in this system, including the relationship between these ARTs and parental care. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702251 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702251">Read the Article</a></i> </p> --> <p><b>Pierson et al. describe alternative reproductive tactics and morphologies in a plethodontid salamander </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 populations of many organisms, several discrete reproductive tactics (called “alternative reproductive tactics” or “ARTs”) coexist. Often, these divergent tactics can be identified by different morphologies. The lungless salamanders (Family Plethodontidae) are a diverse group of amphibians with a center of diversity in the Appalachian Mountains of North America. Prior to the external transfer of a spermatophore, most male plethodontid salamanders court females through the performance of a ritualized “dance” and the delivery of complex reproductive pheromones. While these behaviors are variable among species, they are typically conserved within species. </p><p>In this paper, Todd W. Pierson (University of Tennessee Knoxville), Jennifer Deitloff (Lock&nbsp;Haven University), Stanley K. Sessions (Hartwick College), Kenneth H. Kozak (University of Minnesota), and Benjamin M. Fitzpatrick (University of Tennessee Knoxville) use a combination of genetic, behavioral, and field observational data to describe an example of alternative reproductive tactics in a group of plethodontid salamanders&mdash;the two-lined salamander (<i>Eurycea bislineata</i>) species complex. &ldquo;Searching&rdquo; males have morphological traits and behaviors suited for locating and courting females in terrestrial habitats, while &ldquo;guarding&rdquo; males have morphological traits and behaviors suited for guarding females at aquatic nesting sites. Pierson et al. demonstrate that these two forms coexist in three putative species in the <i>E.&nbsp;bislineata</i> species complex, while other species in the group have only form or the other. The authors also demonstrate that these alternative reproductive tactics have divergent reproductive phenologies, describe the potential implications for parental care, and highlight directions for future research on this system.</p><hr/> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">U</span>nderstanding polymorphism is a central problem in evolution and ecology, and alternative reproductive tactics (ARTs) provide compelling examples for studying the origin and maintenance of behavioral and morphological variation. Much attention has been given to examples where &ldquo;parasitic&rdquo; individuals exploit the reproductive investment of &ldquo;bourgeois&rdquo; individuals, but some ARTs are instead maintained by environmental heterogeneity, with alternative tactics exhibiting differential fitness in discontinuous reproductive niches. We use genomic, behavioral, karyological, and field observational data to demonstrate one such example in plethodontid salamanders. These ARTs (&ldquo;searching&rdquo; and &ldquo;guarding&rdquo; males) are associated with different reproductive niches and, unlike most other examples in amphibians, demonstrate substantial morphological differences and inflexibility within a reproductive season. Evidence suggests the existence of these ARTs within three putative species in the two-lined salamander (<i>Eurycea bislineata</i>) species complex, with other members of this clade fixed for one of the two tactics. We highlight directions for future research in this system, including the relationship between these ARTs and parental care.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 18 Dec 2018 06:00:00 GMT “Time explains regional richness patterns within clades more often than diversification rates or area” https://amnat.org/an/newpapers/AprHongLi.html The DOI will be https://dx.doi.org/10.1086/702253 Across plants and animals, patterns of richness among regions are largely explained by when each region was colonized Why do groups of organisms have different numbers of species in different geographic regions? For example, why do many plant and animal families have more species in tropical regions? For centuries, understanding these patterns of species richness has been a central focus of ecology. For decades, one of the most important hypotheses has been that larger regions have more species. In a new study, scientists now show that these biodiversity patterns typically have a simple explanation, which is unrelated to the area of different regions.In a new paper, Hong Li and John Wiens test why some regions have more species than others. Working at the University of Arizona, they analyzed data from 15 groups of organisms, including plants and animals and marine, freshwater, and terrestrial organisms. Despite the divere organisms and habitats, they found that differences in species numbers among regions almost always had the same explanation: regions with more species were ones that the group colonized earlier. Furthermore, these species richness patterns were only rarely explained by how quickly species proliferated in each region, or how often each region was colonized. Most surprisingly, species numbers were generally unrelated to how large each region was. This finding overturns one of the most important ecological principles of the last 50 years: that larger areas have more species. However, their findings have a simple explanation. Building up large species numbers in a region can take millions of years. Therefore, if a region is colonized more recently, there may simply be too little time to accumulate species there, no matter how large the region is. Overall, the study shows that time is a major factor that underlies species richness patterns in plants and animals around the world. Abstract Most groups of organisms occur in multiple regions, and have different numbers of species in different regions. These richness patterns are directly explained by speciation, extinction, and dispersal. Thus, regional richness patterns may be explained by differences in when regions were colonized (more time-for-speciation in regions colonized earlier), how often they were colonized, or differences in diversification rates (speciation – extinction) among regions (with diversification rates potentially influenced by area, climate, and/or many other variables). Few studies have tested all three factors, and most that did examined them only in individual clades. Here, we analyze a diverse set of 15 clades of plants and animals to test the causes of regional species richness patterns within clades. We find that time was the sole variable significantly explaining richness patterns in the best-fitting models for most clades (10/15), whereas time combined with other factors explained richness in all others. Time was the most important factor explaining richness in 13 of 15 clades, and explained 72% of the variance in species richness among regions across all 15 clades (on average). Surprisingly, time was increasingly important in older and larger clades. In contrast, the area of the regions was relatively unimportant for explaining these regional richness patterns. A systematic review yielded 15 other relevant studies, which also overwhelmingly supported time over diversification rates (13 to 1, with one study supporting both diversification rates and time). Overall, our results suggest that colonization time is a major factor explaining regional-scale richness patterns within clades (e.g., families). More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/702253 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/702253">Read the Article</a></i> </p> --> <p><b>Across plants and animals, patterns of richness among regions are largely explained by when each region was colonized </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hy do groups of organisms have different numbers of species in different geographic regions? For example, why do many plant and animal families have more species in tropical regions? For centuries, understanding these patterns of species richness has been a central focus of ecology. For decades, one of the most important hypotheses has been that larger regions have more species. In a new study, scientists now show that these biodiversity patterns typically have a simple explanation, which is unrelated to the area of different regions.</p><p>In a new paper, Hong Li and John Wiens test why some regions have more species than others. Working at the University of Arizona, they analyzed data from 15 groups of organisms, including plants and animals and marine, freshwater, and terrestrial organisms. Despite the divere organisms and habitats, they found that differences in species numbers among regions almost always had the same explanation: regions with more species were ones that the group colonized earlier. Furthermore, these species richness patterns were only rarely explained by how quickly species proliferated in each region, or how often each region was colonized. </p> <p>Most surprisingly, species numbers were generally unrelated to how large each region was. This finding overturns one of the most important ecological principles of the last 50 years: that larger areas have more species. However, their findings have a simple explanation. Building up large species numbers in a region can take millions of years. Therefore, if a region is colonized more recently, there may simply be too little time to accumulate species there, no matter how large the region is. Overall, the study shows that time is a major factor that underlies species richness patterns in plants and animals around the world.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ost groups of organisms occur in multiple regions, and have different numbers of species in different regions. These richness patterns are directly explained by speciation, extinction, and dispersal. Thus, regional richness patterns may be explained by differences in when regions were colonized (more time-for-speciation in regions colonized earlier), how often they were colonized, or differences in diversification rates (speciation – extinction) among regions (with diversification rates potentially influenced by area, climate, and/or many other variables). Few studies have tested all three factors, and most that did examined them only in individual clades. Here, we analyze a diverse set of 15 clades of plants and animals to test the causes of regional species richness patterns within clades. We find that time was the sole variable significantly explaining richness patterns in the best-fitting models for most clades (10/15), whereas time combined with other factors explained richness in all others. Time was the most important factor explaining richness in 13 of 15 clades, and explained 72% of the variance in species richness among regions across all 15 clades (on average). Surprisingly, time was increasingly important in older and larger clades. In contrast, the area of the regions was relatively unimportant for explaining these regional richness patterns. A systematic review yielded 15 other relevant studies, which also overwhelmingly supported time over diversification rates (13 to 1, with one study supporting both diversification rates and time). Overall, our results suggest that colonization time is a major factor explaining regional-scale richness patterns within clades (e.g., families). </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, 18 Dec 2018 06:00:00 GMT “Grow where you thrive, or where only you can survive? An analysis of performance curve evolution in a clade with diverse habitat affinities” https://amnat.org/an/newpapers/AprTittes.html The DOI will be https://dx.doi.org/10.1086/701827 Do organisms live in environments where they do best, or are they simply persisting in environments they can tolerate? Discovering why organisms live where they do has motivated biologists for centuries and continues to be a major area of research today. In a paper appearing in The American Naturalist, Tittes et al. examined the processes that determine where different species of the annual wildflower group called Goldfields (genus Lasthenia) grow across flooding gradients in seasonal wetlands called vernal pools. Despite being very closely related to one another, having almost identical life cycles, and growing within meters of one another in the field, different taxa occupy different microhabitats across vernal pool flooding gradients: some are always found in deeper positions within pools, while others occur at intermediate depths, and still others occur only in the uplands. The authors sought to understand if their positions in vernal pool landscapes could be predicted strictly by their performance in response to water levels. To do this, Tittes et al. developed a new method to compare how different organisms perform across environmental gradients. They used this method to quantify the performances of 14 Goldfield taxa that were raised under controlled water treatments that ranged from extreme drought to extended flooding. Finally, they evaluated if each taxon performed best under the conditions that matched those of its natural habitat. Surprisingly, they found that all taxa had remarkably similar responses to flooding and drought, and performed best when grown in saturated soil without flooding. Thus, even though different taxa occupy microhabitats with very different water conditions, their responses to water alone do not determine where they occur in vernal pool landscapes. Instead, plant size was the best predictor of the places the different taxa live, perhaps because larger plants are more capable of competing in the environments that all taxa would find optimal. Abstract Performance curves are valuable tools for quantifying the fundamental niches of organisms and testing hypotheses about evolution, life history trade-offs, and the drivers of variation in species’ distribution patterns. Here, we present a novel Bayesian method for characterizing performance curves that facilitates comparisons among species. We then use this model to quantify and compare the hydrological performance curves of 14 different taxa in the genus Lasthenia, an ecologically diverse clade of plants that collectively occupy a variety of habitats with unique hydrological features, including seasonally flooded wetlands called vernal pools. We conducted a growth chamber experiment to measure each taxon’s fitness across five hydrological treatments that ranged from severe drought to extended flooding, and identified differences in hydrological performance curves that explain their associations with vernal pool and terrestrial habitats. Our analysis revealed that the distribution of vernal pool taxa in the field do not reflect their optimal hydrological environments: all taxa, regardless of habitat affinity, have highest fitness under similar hydrological conditions of saturated soil without submergence. We also found that a taxon’s relative position across flood gradients within vernal pools is best predicted by the height of its performance curve. These results demonstrate the utility of our approach for generating insights into when and how performance curves evolve among taxa as they diversify into distinct environments. To facilitate its use, the modeling framework has been developed into an R package (https://github.com/silastittes/performr). More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701827 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701827">Read the Article</a></i> </p> --><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">D</span>o organisms live in environments where they do best, or are they simply persisting in environments they can tolerate? Discovering why organisms live where they do has motivated biologists for centuries and continues to be a major area of research today. </p><p>In a paper appearing in <i>The American Naturalist</i>, Tittes et al. examined the processes that determine where different species of the annual wildflower group called Goldfields (genus <i>Lasthenia</i>) grow across flooding gradients in seasonal wetlands called vernal pools. Despite being very closely related to one another, having almost identical life cycles, and growing within meters of one another in the field, different taxa occupy different microhabitats across vernal pool flooding gradients: some are always found in deeper positions within pools, while others occur at intermediate depths, and still others occur only in the uplands. The authors sought to understand if their positions in vernal pool landscapes could be predicted strictly by their performance in response to water levels. To do this, Tittes et al. developed a new method to compare how different organisms perform across environmental gradients. They used this method to quantify the performances of 14 Goldfield taxa that were raised under controlled water treatments that ranged from extreme drought to extended flooding. Finally, they evaluated if each taxon performed best under the conditions that matched those of its natural habitat. </p><p>Surprisingly, they found that all taxa had remarkably similar responses to flooding and drought, and performed best when grown in saturated soil without flooding. Thus, even though different taxa occupy microhabitats with very different water conditions, their responses to water alone do not determine where they occur in vernal pool landscapes. Instead, plant size was the best predictor of the places the different taxa live, perhaps because larger plants are more capable of competing in the environments that all taxa would find optimal. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>erformance curves are valuable tools for quantifying the fundamental niches of organisms and testing hypotheses about evolution, life history trade-offs, and the drivers of variation in species’ distribution patterns. Here, we present a novel Bayesian method for characterizing performance curves that facilitates comparisons among species. We then use this model to quantify and compare the hydrological performance curves of 14 different taxa in the genus <i>Lasthenia</i>, an ecologically diverse clade of plants that collectively occupy a variety of habitats with unique hydrological features, including seasonally flooded wetlands called vernal pools. We conducted a growth chamber experiment to measure each taxon’s fitness across five hydrological treatments that ranged from severe drought to extended flooding, and identified differences in hydrological performance curves that explain their associations with vernal pool and terrestrial habitats. Our analysis revealed that the distribution of vernal pool taxa in the field do not reflect their optimal hydrological environments: all taxa, regardless of habitat affinity, have highest fitness under similar hydrological conditions of saturated soil without submergence. We also found that a taxon’s relative position across flood gradients within vernal pools is best predicted by the height of its performance curve. These results demonstrate the utility of our approach for generating insights into when and how performance curves evolve among taxa as they diversify into distinct environments. To facilitate its use, the modeling framework has been developed into an R package (<a href="https://github.com/silastittes/performr">https://github.com/silastittes/performr</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, 05 Dec 2018 06:00:00 GMT “Stage-structured evolutionary demography: linking life histories, population genetics, and ecological dynamics” https://amnat.org/an/newpapers/AprDeVries.html The DOI will be https://dx.doi.org/10.1086/701857 Wouldn’t it be nice if population genetics and stage-classified demography got together? Now they have This lesser world is all about reproduction, as you might well know. Those who cease to duplicate simply die.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;—Rawi Hage, Carnival Organisms are born and they die. These processes change the size and structure of populations as well as their genetic make-up. Demography (the rates of birth, death, aging, development, etc.) is thus crucial to evolution. Yet many of these rates have been neglected or ignored in traditional population genetics, which has generally focused on survival rates only (an assumption known as “viability selection”). A central question for genetics is whether one gene will come to dominate the population, or whether multiple genetic types will coexist in what is called a genetic polymorphism. What determines coexistence of genes when demographic processes are included? Answering this question requires a model that keeps track of individuals of different ages or sizes as well as their genetic make-up. Charlotte de Vries and Hal Caswell from the University of Amsterdam introduce such a model. It connects a powerful set of demographic methods (known as matrix population models) to basic Mendelian genetics. The authors use their model for two purposes. First, they show how to calculate the way that population size, structure, and genetics will change over time, taking into account births, deaths, and development. Second, they derive new, and very general, conditions that lead to coexistence of genetic types in a polymorphism. The results of more traditional genetic analyses appear as special cases, but the authors’ new results are more general. These results provide a new framework for analyzing the evolution of life histories of plants, animals, and humans. As an example, the authors apply their model to a study of genetically determined color polymorphism in the common buzzard, Buteo buteo. Abstract Demographic processes and ecological interactions are central to understanding evolution, and vice versa. We present a novel framework that combines basic Mendelian genetics with the powerful demographic approach of matrix population models. The demographic component of the model may be stage-classified or age-classified, linear or nonlinear, time-invariant or time varying, deterministic or stochastic, and may include dependence on environmental resources or interactions among species. Genotypes may affect, in fully pleiotropic fashion, any mixture of demographic traits (viability, fertility, development) at any points in the life cycle. The dynamics of the stage&nbsp;&times;&nbsp;genotype structure of the population are given by a nonlinear population projection matrix. We show how to construct this matrix and use it to derive sufficient conditions for a protected genetic polymorphism for the case of linear, time-independent demography. These conditions demonstrate that genotype-specific population population growth rates (&lambda;) do not determine the outcome of selection. Except in restrictive special cases, heterozygote superiority in &lambda; is neither necessary nor sufficient for a genetic polymorphism. As a consequence, population growth rate does not always increase and populations can be driven to extinction due to evolutionary suicide. We demonstrate the construction and analysis of the model using data on a color polymorphism in the common buzzard, Buteo buteo. The model exhibits a stable genetic polymorphism and declining growth rate, consistent with field data and previous models. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701857 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701857">Read the Article</a></i> </p> --> <p><b>Wouldn’t it be nice if population genetics and stage-classified demography got together? Now they have </b></p> <blockquote>This lesser world is all about reproduction, as you might well know. Those who cease to duplicate simply die.<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&mdash;Rawi Hage, <i>Carnival</i> </blockquote><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>rganisms are born and they die. These processes change the size and structure of populations as well as their genetic make-up. Demography (the rates of birth, death, aging, development, etc.) is thus crucial to evolution. Yet many of these rates have been neglected or ignored in traditional population genetics, which has generally focused on survival rates only (an assumption known as &ldquo;viability selection&rdquo;). A central question for genetics is whether one gene will come to dominate the population, or whether multiple genetic types will coexist in what is called a genetic polymorphism. What determines coexistence of genes when demographic processes are included? Answering this question requires a model that keeps track of individuals of different ages or sizes as well as their genetic make-up. Charlotte de Vries and Hal Caswell from the University of Amsterdam introduce such a model. It connects a powerful set of demographic methods (known as matrix population models) to basic Mendelian genetics. </p><p>The authors use their model for two purposes. First, they show how to calculate the way that population size, structure, and genetics will change over time, taking into account births, deaths, and development. Second, they derive new, and very general, conditions that lead to coexistence of genetic types in a polymorphism. The results of more traditional genetic analyses appear as special cases, but the authors&rsquo; new results are more general. These results provide a new framework for analyzing the evolution of life histories of plants, animals, and humans. As an example, the authors apply their model to a study of genetically determined color polymorphism in the common buzzard, <i>Buteo buteo</i>.</p><hr/> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">D</span>emographic processes and ecological interactions are central to understanding evolution, and vice versa. We present a novel framework that combines basic Mendelian genetics with the powerful demographic approach of matrix population models. The demographic component of the model may be stage-classified or age-classified, linear or nonlinear, time-invariant or time varying, deterministic or stochastic, and may include dependence on environmental resources or interactions among species. Genotypes may affect, in fully pleiotropic fashion, any mixture of demographic traits (viability, fertility, development) at any points in the life cycle. The dynamics of the stage&nbsp;&times;&nbsp;genotype structure of the population are given by a nonlinear population projection matrix. We show how to construct this matrix and use it to derive sufficient conditions for a protected genetic polymorphism for the case of linear, time-independent demography. These conditions demonstrate that genotype-specific population population growth rates (&lambda;) do not determine the outcome of selection. Except in restrictive special cases, heterozygote superiority in &lambda; is neither necessary nor sufficient for a genetic polymorphism. As a consequence, population growth rate does not always increase and populations can be driven to extinction due to evolutionary suicide. We demonstrate the construction and analysis of the model using data on a color polymorphism in the common buzzard, <i>Buteo buteo</i>. The model exhibits a stable genetic polymorphism and declining growth rate, consistent with field data and previous models.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 05 Dec 2018 06:00:00 GMT “Effects of predator avoidance behavior on the coexistence of competing prey” https://amnat.org/an/newpapers/MaySommers.html The DOI will be https://dx.doi.org/10.1086/701780 General rules of how predator avoidance behavior alters coexistence of similar species with shared predators and resources If you have ever tried to catch a lizard or other small creature, you know that animals go out of their way to avoid potential predators. While busy hiding or escaping, however, an animal cannot also search for food and could starve to death from spending too much time avoiding predation. In this way, predators affect their prey not only by killing them, but by scaring them into changing their eating habits. A growing number of studies have shown how scaring prey can affect the stability of the whole ecosystem. Now researchers have shown how predator avoidance behavior affects a classic puzzle in ecology: why there are so many species. The puzzle goes like this: if similar species are competing for resources, why have a few super-competitors not taken over the world? One reason is that all species face trade-offs, and differentiate themselves in some way, finding their own unique ecological niches which result in a diversity of species. New research published in The&nbsp;American Naturalist uses mathematical models to derive general rules for when avoiding predators increases biological diversity, and when it decreases diversity. In the model, those unique niches of each species can overlap to various degrees in terms of the resources they use and the predators that hunt them. Hiding from the predators reduces the effect of predator overlap on coexistence. For two species with the same predators that rely on very different resources, avoiding predators increases the species’ niche partitioning, generally promoting biodiversity. On the other hand, if two species rely on the same resources and predator partitioning would maintain their coexistence, then hiding from predators undermines diversity by making the superior competitor more likely to exclude the other species. Which competitor is superior also depends on the avoidance behavior, and the authors derive the conditions under which each species benefits more from hiding. The study derives general rules for how a common behavior affects a classic puzzle about biodiversity and competition. These rules can be applied to a variety of ecosystems. As humans continue to change landscapes and eliminate predators, understanding general rules of how biodiversity may be affected will help predict the impacts – and maybe suggest future solutions. Abstract Predator avoidance behavior, in which prey limit foraging activities in the presence of predation threats, affects the dynamics of many ecological communities. Despite the growing theoretical appreciation of the role predation plays in coexistence, predator avoidance behavior has yet to be incorporated into the theory in a general way. We introduce adaptive avoidance behavior to a consumer-resource model with three trophic levels to ask whether the ability of prey, the middle trophic level, to avoid predators alters their ability to coexist. We determine the characteristics of cases in which predator avoidance behavior changes prey coexistence, or the order of competitive dominance. The mechanism underlying such changes is the weakening of apparent competition relative to resource competition in determining niche overlap, even with resource intake costs. Avoidance behavior thus generally promotes coexistence if prey partition resources but not predators, whereas it undermines coexistence if prey partition predators but not resources. For any given case, the changes in the average fitness difference between two species resulting from avoidance behavior interact with changes in niche overlap to determine coexistence. These results connect the substantial body of theoretical work on avoidance behavior and population dynamics with the body of theory on competitive coexistence. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701780 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701780">Read the Article</a></i> </p> --> <p><b>General rules of how predator avoidance behavior alters coexistence of similar species with shared predators and resources </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>f you have ever tried to catch a lizard or other small creature, you know that animals go out of their way to avoid potential predators. While busy hiding or escaping, however, an animal cannot also search for food and could starve to death from spending too much time avoiding predation. In this way, predators affect their prey not only by killing them, but by scaring them into changing their eating habits. A growing number of studies have shown how scaring prey can affect the stability of the whole ecosystem. Now researchers have shown how predator avoidance behavior affects a classic puzzle in ecology: why there are so many species. The puzzle goes like this: if similar species are competing for resources, why have a few super-competitors not taken over the world? One reason is that all species face trade-offs, and differentiate themselves in some way, finding their own unique ecological niches which result in a diversity of species.</p> <p>New research published in <i>The&nbsp;American Naturalist</i> uses mathematical models to derive general rules for when avoiding predators increases biological diversity, and when it decreases diversity. In the model, those unique niches of each species can overlap to various degrees in terms of the resources they use and the predators that hunt them. Hiding from the predators reduces the effect of predator overlap on coexistence. For two species with the same predators that rely on very different resources, avoiding predators increases the species’ niche partitioning, generally promoting biodiversity. On the other hand, if two species rely on the same resources and predator partitioning would maintain their coexistence, then hiding from predators undermines diversity by making the superior competitor more likely to exclude the other species. Which competitor is superior also depends on the avoidance behavior, and the authors derive the conditions under which each species benefits more from hiding. The study derives general rules for how a common behavior affects a classic puzzle about biodiversity and competition. These rules can be applied to a variety of ecosystems. As humans continue to change landscapes and eliminate predators, understanding general rules of how biodiversity may be affected will help predict the impacts – and maybe suggest future solutions.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>redator avoidance behavior, in which prey limit foraging activities in the presence of predation threats, affects the dynamics of many ecological communities. Despite the growing theoretical appreciation of the role predation plays in coexistence, predator avoidance behavior has yet to be incorporated into the theory in a general way. We introduce adaptive avoidance behavior to a consumer-resource model with three trophic levels to ask whether the ability of prey, the middle trophic level, to avoid predators alters their ability to coexist. We determine the characteristics of cases in which predator avoidance behavior changes prey coexistence, or the order of competitive dominance. The mechanism underlying such changes is the weakening of apparent competition relative to resource competition in determining niche overlap, even with resource intake costs. Avoidance behavior thus generally promotes coexistence if prey partition resources but not predators, whereas it undermines coexistence if prey partition predators but not resources. For any given case, the changes in the average fitness difference between two species resulting from avoidance behavior interact with changes in niche overlap to determine coexistence. These results connect the substantial body of theoretical work on avoidance behavior and population dynamics with the body of theory on competitive coexistence. </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, 05 Dec 2018 06:00:00 GMT “The evolutionary ecology of metamorphosis” https://amnat.org/an/newpapers/MayTenBrink.html The DOI will be https://dx.doi.org/10.1086/701779 Why is metamorphosis widespread in the animal kingdom, despite a few evolutionary origins? It is an evolutionary trap! A&nbsp;butterfly slowly emerges from its chrysalis, revealing its colorful wings. Not that long ago, this butterfly was a fat caterpillar, gorging itself on juicy leaves. It then molted into a pupa, ready to metamorphose itself into an elegant butterfly. Metamorphosis occurs not only in butterflies, but in the majority of all animal species. Why has metamorphosis evolved and why is it so pervasive in the animal kingdom? In this study, ten Brink, de Roos, and Dieckmann show with a mathematical model that metamorphosis can only evolve under limited ecological conditions. During metamorphosis, individuals rebuild their body plan. The benefit of this is that larvae and adults have different morphologies, each specialized in feeding on different food types. Metamorphosis is, however, energetically very costly and also dangerous (a pupa can, for example, not run away from a predator). Metamorphosis will therefore only evolve when the benefits of having a metamorphosis are very high. This is the case when individuals have access to an abundant food source after metamorphosis. Surprisingly, the researchers find that species with a metamorphosis will not abandon this life-history strategy when the ecological conditions change under which metamorphosis initially evolved. The reason for this is that individuals are, after metamorphosis, not very efficient in feeding on the food source they ate as larvae. Metamorphosed individuals can therefore not easily switch back to this larval food source in case the food type they feed on becomes scarce. Instead, there is selection to become even more specialized in feeding on this limited food, resulting in a more pronounced metamorphosis and more dissimilar life-stages. The findings in this study can explain the widespread occurrence of metamorphosis, despite only a few evolutionary origins. Abstract Almost all animal species undergo metamorphosis, even though empirical data show that this life-history strategy evolved only a few times. Why is metamorphosis so widespread and why has it evolved? Here we study the evolution of metamorphosis using a fully size-structured population model in conjunction with the adaptive-dynamics approach. We assume that individuals compete for two food sources, one of these, the primary food source, is available to individuals of all sizes. The secondary food source is available only to large individuals. Without metamorphosis, unresolvable tensions arise for species faced with the opportunity of specializing on such a secondary food source. We show that metamorphosis can evolve as a way to resolve these tensions, such that small individuals specialize on the primary food source, while large individuals specialize on the secondary food source. We find, however, that metamorphosis only evolves when the supply rate of the secondary food source exceeds a high threshold. Individuals postpone metamorphosis when the ecological conditions under which metamorphosis originally evolved deteriorate but will often not abandon this life-history strategy, even if it causes population extinction through evolutionary trapping. In summary, our results show that metamorphosis is not easy to evolve but, once evolved, it is hard to lose. These findings can explain the widespread occurrence of metamorphosis in the animal kingdom despite its few evolutionary origins. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701779 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701779">Read the Article</a></i> </p> --> <p><b>Why is metamorphosis widespread in the animal kingdom, despite a few evolutionary origins? It is an evolutionary trap! </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;">A</span>&nbsp;butterfly slowly emerges from its chrysalis, revealing its colorful wings. Not that long ago, this butterfly was a fat caterpillar, gorging itself on juicy leaves. It then molted into a pupa, ready to metamorphose itself into an elegant butterfly. Metamorphosis occurs not only in butterflies, but in the majority of all animal species. Why has metamorphosis evolved and why is it so pervasive in the animal kingdom?</p> <p>In this study, ten Brink, de Roos, and Dieckmann show with a mathematical model that metamorphosis can only evolve under limited ecological conditions. During metamorphosis, individuals rebuild their body plan. The benefit of this is that larvae and adults have different morphologies, each specialized in feeding on different food types. Metamorphosis is, however, energetically very costly and also dangerous (a pupa can, for example, not run away from a predator). Metamorphosis will therefore only evolve when the benefits of having a metamorphosis are very high. This is the case when individuals have access to an abundant food source after metamorphosis.</p> <p>Surprisingly, the researchers find that species with a metamorphosis will not abandon this life-history strategy when the ecological conditions change under which metamorphosis initially evolved. The reason for this is that individuals are, after metamorphosis, not very efficient in feeding on the food source they ate as larvae. Metamorphosed individuals can therefore not easily switch back to this larval food source in case the food type they feed on becomes scarce. Instead, there is selection to become even more specialized in feeding on this limited food, resulting in a more pronounced metamorphosis and more dissimilar life-stages. The findings in this study can explain the widespread occurrence of metamorphosis, despite only a few evolutionary origins.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>lmost all animal species undergo metamorphosis, even though empirical data show that this life-history strategy evolved only a few times. Why is metamorphosis so widespread and why has it evolved? Here we study the evolution of metamorphosis using a fully size-structured population model in conjunction with the adaptive-dynamics approach. We assume that individuals compete for two food sources, one of these, the primary food source, is available to individuals of all sizes. The secondary food source is available only to large individuals. Without metamorphosis, unresolvable tensions arise for species faced with the opportunity of specializing on such a secondary food source. We show that metamorphosis can evolve as a way to resolve these tensions, such that small individuals specialize on the primary food source, while large individuals specialize on the secondary food source. We find, however, that metamorphosis only evolves when the supply rate of the secondary food source exceeds a high threshold. Individuals postpone metamorphosis when the ecological conditions under which metamorphosis originally evolved deteriorate but will often not abandon this life-history strategy, even if it causes population extinction through evolutionary trapping. In summary, our results show that metamorphosis is not easy to evolve but, once evolved, it is hard to lose. These findings can explain the widespread occurrence of metamorphosis in the animal kingdom despite its few evolutionary origins.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 05 Dec 2018 06:00:00 GMT “Two-year bee, or not two-year bee? How voltinism is affected by temperature and season length in a high-elevation solitary bee” https://amnat.org/an/newpapers/AprForrest.html The DOI will be https://dx.doi.org/10.1086/701826 Faced with short and variable summers, mason bee larvae use temperature & birth date to decide on 1- or 2-year life cycle Animals never know exactly what their future holds when it comes to environmental conditions—yet, when faced with alternatives, they often make the correct decision. For example, some solitary bees can become adults one or two years after hatching from eggs. But how does a bee decide which strategy is best? It’s a tough choice because one-year bees reproduce earlier than their two-year compatriots, but a one-year bee caught mid-metamorphosis when winter arrives will die. Therefore, it’s safer, but less rewarding, to be a two-year bee. Jessica Forrest became interested in this observation while studying mason bees in the Rocky Mountains, USA. Fellow ecologist Paul CaraDonna shared similar observations, and the two started to ponder what caused the phenomenon. With the help of undergraduate researcher Regan Cross, they set out to determine if temperature or summer season length determines whether bees opt for one- or two-year life cycles. By moving bee eggs from the field to incubators and manipulating temperature and season lengths, the team found that warmer—but not longer—summers, combined with earlier birth dates, increased the frequency of one-year bees. With this knowledge in hand, the researchers looked at local climate records, and found that only 7% of summers since 1950 have been warm enough for one-year bees to succeed, explaining the observed scarcity of one-year bees in the study area. As temperatures warm under climate change, suitable conditions for one-year life cycles may become more common; nevertheless, since this one-year strategy is still riskier than the two-year strategy, both life cycles will likely persist. This study shows that bee larvae can integrate temperature cues and information on when in the season they were born to make the right decision about which life cycle to pursue. Just how they are able to do this remains a mystery. Abstract Organisms must often make developmental decisions without complete information about future conditions. This uncertainty—for example, about the duration of conditions favorable for growth—can favor bet-hedging strategies. Here, we investigated the causes of life-cycle variation in Osmia iridis, a bee exhibiting a possible bet-hedging strategy with co-occurring one- and two-year life cycles. One-year bees reach adulthood quickly but die if they fail to complete pupation before winter; two-year bees adopt a low-risk, low-reward strategy of postponing pupation until the second summer. We reared larval bees in incubators in various experimental conditions and found that warmer—but not longer—summers, and early birth dates, increased the frequency of one-year life cycles. Using in situ temperature measurements and developmental trajectories of laboratory- and field-reared bees, we estimated degree-days required to reach adulthood in a single year. Local long-term (1950–2015) climate records reveal that this heat requirement is met in only ~7% of summers, suggesting that the observed distribution of life cycles is adaptive. Warming summers will likely decrease average generation times in these populations. Nevertheless, survival of bees attempting one-year life cycles—particularly those developing from late-laid eggs—will be <100%; consequently, we expect the life-cycle polymorphism to persist. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701826 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701826">Read the Article</a></i> </p> --> <p><b>Faced with short and variable summers, mason bee larvae use temperature & birth date to decide on 1- or 2-year life cycle </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>nimals never know exactly what their future holds when it comes to environmental conditions—yet, when faced with alternatives, they often make the correct decision. </p><p>For example, some solitary bees can become adults one <i>or</i> two years after hatching from eggs. But how does a bee decide which strategy is best? It’s a tough choice because one-year bees reproduce earlier than their two-year compatriots, but a one-year bee caught mid-metamorphosis when winter arrives will die. Therefore, it’s safer, but less rewarding, to be a two-year bee. </p><p>Jessica Forrest became interested in this observation while studying mason bees in the Rocky Mountains, USA. Fellow ecologist Paul CaraDonna shared similar observations, and the two started to ponder what caused the phenomenon. With the help of undergraduate researcher Regan Cross, they set out to determine if temperature or summer season length determines whether bees opt for one- or two-year life cycles. By moving bee eggs from the field to incubators and manipulating temperature and season lengths, the team found that warmer—but not longer—summers, combined with earlier birth dates, increased the frequency of one-year bees. </p><p>With this knowledge in hand, the researchers looked at local climate records, and found that only 7% of summers since 1950 have been warm enough for one-year bees to succeed, explaining the observed scarcity of one-year bees in the study area. As temperatures warm under climate change, suitable conditions for one-year life cycles may become more common; nevertheless, since this one-year strategy is still riskier than the two-year strategy, both life cycles will likely persist. This study shows that bee larvae can integrate temperature cues and information on when in the season they were born to make the right decision about which life cycle to pursue. Just how they are able to do this remains a mystery.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">O</span>rganisms must often make developmental decisions without complete information about future conditions. This uncertainty&mdash;for example, about the duration of conditions favorable for growth&mdash;can favor bet-hedging strategies. Here, we investigated the causes of life-cycle variation in <i>Osmia iridis</i>, a bee exhibiting a possible bet-hedging strategy with co-occurring one- and two-year life cycles. One-year bees reach adulthood quickly but die if they fail to complete pupation before winter; two-year bees adopt a low-risk, low-reward strategy of postponing pupation until the second summer. We reared larval bees in incubators in various experimental conditions and found that warmer&mdash;but not longer&mdash;summers, and early birth dates, increased the frequency of one-year life cycles. Using in situ temperature measurements and developmental trajectories of laboratory- and field-reared bees, we estimated degree-days required to reach adulthood in a single year. Local long-term (1950&ndash;2015) climate records reveal that this heat requirement is met in only ~7% of summers, suggesting that the observed distribution of life cycles is adaptive. Warming summers will likely decrease average generation times in these populations. Nevertheless, survival of bees attempting one-year life cycles&mdash;particularly those developing from late-laid eggs&mdash;will be &lt;100%; consequently, we expect the life-cycle polymorphism to persist.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 05 Dec 2018 06:00:00 GMT “The relationship between spatial structure and the maintenance of diversity in microbial populations” https://amnat.org/an/newpapers/AprFrance-A.html The DOI will be https://dx.doi.org/10.1086/701799 Abstract Spatial structure is pervasive in the microbial world, yet we know little about how it influences the evolution of microbial populations. It is thought that spatial structure limits the scale of competitive interactions and protracts selective sweeps. This may allow microbial populations to simultaneously explore multiple evolutionary paths. But how structured a microbial population must be before this effect is realized is not known. We used empirical and simulation studies to explore the relationship between spatial structure and the maintenance of diversity. The degree of spatial structure experienced by Escherichia coli metapopulations was manipulated by varying the migration rate between its component subpopulations. Each subpopulation was inoculated with an equal number of two equally fit genotypes and their frequencies in 12 subpopulations were determined during 150 generations of evolution. We observed that the frequency of the ‘loser’ genotypes decreased exponentially as the migration rate between the subpopulations was increased and that higher frequencies of the ‘loser’ genotypes were maintained in structured metapopulations. These results demonstrate that structured microbial populations can evolve along multiple evolutionary trajectories even when migration rates between the subpopulations are relatively high. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701799 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701799">Read the Article</a></i> </p> --><!-- <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span> </p> <hr /> --> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>patial structure is pervasive in the microbial world, yet we know little about how it influences the evolution of microbial populations. It is thought that spatial structure limits the scale of competitive interactions and protracts selective sweeps. This may allow microbial populations to simultaneously explore multiple evolutionary paths. But how structured a microbial population must be before this effect is realized is not known. We used empirical and simulation studies to explore the relationship between spatial structure and the maintenance of diversity. The degree of spatial structure experienced by <i>Escherichia coli</i> metapopulations was manipulated by varying the migration rate between its component subpopulations. Each subpopulation was inoculated with an equal number of two equally fit genotypes and their frequencies in 12 subpopulations were determined during 150 generations of evolution. We observed that the frequency of the ‘loser’ genotypes decreased exponentially as the migration rate between the subpopulations was increased and that higher frequencies of the ‘loser’ genotypes were maintained in structured metapopulations. These results demonstrate that structured microbial populations can evolve along multiple evolutionary trajectories even when migration rates between the subpopulations are relatively high. </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, 05 Dec 2018 06:00:00 GMT “Rapid divergence of predator functional traits affects prey composition in aquatic communities” https://amnat.org/an/newpapers/MarSchmid.html The DOI will be https://dx.doi.org/10.1086/701784 Rapid trait evolution in recently diverged predator populations impacts predator performance and prey community structure Darwin was the first to identify that variation in traits amongst individuals is the basis upon which selection can act. But interestingly, trait functionality is often assumed rather than tested empirically (i.e. longer legs equals faster running). Yet many functions, such as prey pursue, capture, and ingestion, require many traits to interact. This makes it difficult to disentangle which traits are key to a specific function. In this paper Dominik W. Schmid, Matt McGee, Rebecca J. Best, Ole Seehausen, and Blake Matthews at EAWAG (Switzerland) have specifically looked into the trait utility (i.e. fitness advantage of traits in a given environmental context) of a predator’s foraging morphology and its consequences for prey capture and community structure. The marine ancestors of threespine stickleback (Gasterosteus aculeatus) repeatedly and independently invaded freshwater rivers and lakes in the Northern Hemisphere. However, the marine ancestor feeds predominantly on zooplankton, a resource typically sparse in rivers. The authors found that the head morphology of riverine stickleback differs remarkably from sticklebacks inhabiting lakes (i.e. a more marine-like environment with lots of zooplankton). When feeding on a natural zooplankton community, the authors determined via foraging tests and subsequent gut content analysis that lake stickleback outperform riverine stickleback in the capture of zooplankton. Furthermore, they linked capture success, particularly of evasive prey, to the degree of jaw protrusion. That means the longer the fish’s jaw protrudes towards the highly evasive zooplankton, the higher the chances of capture. What makes this study so remarkable is the rapidity of adaptive morphological differentiation since the two population sampled only diverged within the last 150 years. In addition, the authors investigated the change in community composition as a consequence of predation by both lake and river-adapted stickleback and found that lake stickleback not only diminished the zooplankton community more readily than their riverine counterparts, but that they target largely predatory and highly evasive zooplankton, thus affecting the community structure and dynamics of their zooplankton prey. These results corroborate findings from a recent large-scale mesocosm experiment (Matthews et al. 2016 Current Biology). This means that traits such as jaw protrusion are a link between prey ecology and predator evolution and a mechanistic basis for feedbacks between the two. Abstract Identifying traits that underlie variation in individual performance of consumers (i.e. trait utility) can help reveal the ecological causes of population divergence, and the subsequent consequences for species interactions and community structure. Here, we document a case of rapid divergence (over the past 100 generations or ~150 years) in foraging traits and feeding efficiency between a lake and stream population pair of threespine stickleback. Building on predictions from functional trait models of fish feeding, we analyzed foraging experiments with a Bayesian path analysis and elucidated the traits explaining variation in foraging performance and the species composition of ingested prey. Despite extensive previous research on the divergence of foraging traits among populations and ecotypes of stickleback, our results provide novel experimental evidence of trait utility for jaw protrusion, gill raker length, and gill raker spacing when foraging on a natural zooplankton assemblage. Furthermore, we discuss how these traits might contribute to the differential effects of lake and stream stickleback on their prey communities, observed in both laboratory and mesocosm conditions. More generally, our results illustrate how the rapid divergence of functional foraging traits of consumers can impact the biomass, species composition, and trophic structure of prey communities. Schnelle &Ouml;kotyp-Bildung eines Fischr&auml;ubers ver&auml;ndert die Zusammensetzung der Zooplanktongemeinschaften Um den Prozess der Artenbildung und dessen Wirkung auf die Struktur und Beziehungen ökologischer Gemeinschaften besser verstehen zu können, benötigt es detailierte Studien von Merkmalsvariationen und deren Funktionalität unter natürlichen Bedingungen. Wir dokumentieren hier den Fall einer besonders schnellen (~150 Jahre; <100 Generationen) Ökotyp-Formierung von Fluss- und See-angepassten Dreistachligen Stichlingen im Einzugsbereich des Bodensees (Schweiz). Die Ökotypen unterscheiden sich in Bezug auf ihre Kopfmorphologie und Effizienz der Nahrungsaufnahme maßgeblich: See-angepasste Stichlinge verschieben ihren Oberkiefer weiter nach vorne während der Öffnung des Mauls, fangen Zooplanktonbeute mit doppelter Effizienz und bevorzugen Ruderfusskrebse (Copepoda) an Stelle von Wasserflöhen (Cladocera). Interessanterweise lassen sich Variationen im Fraßerfolg auf unterschiedliche Kopfmorphologien zurückführen; genauer gesagt, dem Ausmaß der Verschiebung des Oberkieferansatzes in Richtung der Beute und dem Abstand und der Länge der Bezahnung der Kiemenreusen. Zusätzlich, zeigt sich anhand von Labor- und Mesokosmos-Experimenten, dass Fluss- und See-angepasste Stichlinge die Gemeinschaft an Beutetieren unterschiedlich beeinflussen. Zuammenfassend gibt unsere Studie Aufschluss darüber, weshalb verschiedene Ökotypen der gleichen Art die trophische Struktur, Zusammensetzung und Häufigkeit ihrer Beute gegensätzlich beeinträchtigen können. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701784 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701784">Read the Article</a></i> </p> --> <p><b>Rapid trait evolution in recently diverged predator populations impacts predator performance and prey community structure </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;">D</span>arwin was the first to identify that variation in traits amongst individuals is the basis upon which selection can act. But interestingly, trait functionality is often assumed rather than tested empirically (i.e. longer legs equals faster running). Yet many functions, such as prey pursue, capture, and ingestion, require many traits to interact. This makes it difficult to disentangle which traits are key to a specific function. In this paper Dominik W. Schmid, Matt McGee, Rebecca J. Best, Ole Seehausen, and Blake Matthews at EAWAG (Switzerland) have specifically looked into the trait utility (i.e. fitness advantage of traits in a given environmental context) of a predator&rsquo;s foraging morphology and its consequences for prey capture and community structure.</p> <p>The marine ancestors of threespine stickleback (<i>Gasterosteus aculeatus</i>) repeatedly and independently invaded freshwater rivers and lakes in the Northern Hemisphere. However, the marine ancestor feeds predominantly on zooplankton, a resource typically sparse in rivers. The authors found that the head morphology of riverine stickleback differs remarkably from sticklebacks inhabiting lakes (i.e. a more marine-like environment with lots of zooplankton). When feeding on a natural zooplankton community, the authors determined via foraging tests and subsequent gut content analysis that lake stickleback outperform riverine stickleback in the capture of zooplankton. Furthermore, they linked capture success, particularly of evasive prey, to the degree of jaw protrusion. That means the longer the fish&rsquo;s jaw protrudes towards the highly evasive zooplankton, the higher the chances of capture. What makes this study so remarkable is the rapidity of adaptive morphological differentiation since the two population sampled only diverged within the last 150 years.</p> <p>In addition, the authors investigated the change in community composition as a consequence of predation by both lake and river-adapted stickleback and found that lake stickleback not only diminished the zooplankton community more readily than their riverine counterparts, but that they target largely predatory and highly evasive zooplankton, thus affecting the community structure and dynamics of their zooplankton prey. These results corroborate findings from a recent large-scale mesocosm experiment (Matthews et al. 2016 Current Biology). This means that traits such as jaw protrusion are a link between prey ecology and predator evolution and a mechanistic basis for feedbacks between the two.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">I</span>dentifying traits that underlie variation in individual performance of consumers (i.e. trait utility) can help reveal the ecological causes of population divergence, and the subsequent consequences for species interactions and community structure. Here, we document a case of rapid divergence (over the past 100 generations or ~150 years) in foraging traits and feeding efficiency between a lake and stream population pair of threespine stickleback. Building on predictions from functional trait models of fish feeding, we analyzed foraging experiments with a Bayesian path analysis and elucidated the traits explaining variation in foraging performance and the species composition of ingested prey. Despite extensive previous research on the divergence of foraging traits among populations and ecotypes of stickleback, our results provide novel experimental evidence of trait utility for jaw protrusion, gill raker length, and gill raker spacing when foraging on a natural zooplankton assemblage. Furthermore, we discuss how these traits might contribute to the differential effects of lake and stream stickleback on their prey communities, observed in both laboratory and mesocosm conditions. More generally, our results illustrate how the rapid divergence of functional foraging traits of consumers can impact the biomass, species composition, and trophic structure of prey communities.</p> <h4>Schnelle &Ouml;kotyp-Bildung eines Fischr&auml;ubers ver&auml;ndert die Zusammensetzung der Zooplanktongemeinschaften</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>m den Prozess der Artenbildung und dessen Wirkung auf die Struktur und Beziehungen ökologischer Gemeinschaften besser verstehen zu können, benötigt es detailierte Studien von Merkmalsvariationen und deren Funktionalität unter natürlichen Bedingungen. Wir dokumentieren hier den Fall einer besonders schnellen (~150 Jahre; <100 Generationen) Ökotyp-Formierung von Fluss- und See-angepassten Dreistachligen Stichlingen im Einzugsbereich des Bodensees (Schweiz). Die Ökotypen unterscheiden sich in Bezug auf ihre Kopfmorphologie und Effizienz der Nahrungsaufnahme maßgeblich: See-angepasste Stichlinge verschieben ihren Oberkiefer weiter nach vorne während der Öffnung des Mauls, fangen Zooplanktonbeute mit doppelter Effizienz und bevorzugen Ruderfusskrebse (Copepoda) an Stelle von Wasserflöhen (Cladocera). Interessanterweise lassen sich Variationen im Fraßerfolg auf unterschiedliche Kopfmorphologien zurückführen; genauer gesagt, dem Ausmaß der Verschiebung des Oberkieferansatzes in Richtung der Beute und dem Abstand und der Länge der Bezahnung der Kiemenreusen. Zusätzlich, zeigt sich anhand von Labor- und Mesokosmos-Experimenten, dass Fluss- und See-angepasste Stichlinge die Gemeinschaft an Beutetieren unterschiedlich beeinflussen. Zuammenfassend gibt unsere Studie Aufschluss darüber, weshalb verschiedene Ökotypen der gleichen Art die trophische Struktur, Zusammensetzung und Häufigkeit ihrer Beute gegensätzlich beeinträchtigen können. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 05 Dec 2018 06:00:00 GMT “Speciation rate is independent of the rate of evolution of morphological size, shape, and absolute morphological specialization in a large clade of birds” https://amnat.org/an/newpapers/AprCrouch.html The DOI will be https://dx.doi.org/10.1086/701630 Biodiversity may be limited by division of resources and not just ecological opportunity A&nbsp;basic issue in evolutionary biology is the relationship between the rate of species formation and the rate of morphological diversification. We expect these rates to be correlated because conditions that favor an increase in one commonly accelerates the other. For example, a population that colonizes an island lacking competing species may diversify into new ecological roles while splitting into multiple species. Alternatively, rates of speciation and ecological diversification might not be correlated if descendant species become increasingly ecologically specialized in response to growing competition in diverse communities. In this study, researchers gathered morphological data from over 2000 species from 11 orders of predominantly arboreal birds to test whether speciation and morphological diversification are generally correlated. They found that the size, shape, and morphological specialization are unrelated to rate of diversification. They suggest that this is because most of the variation in the group arose early in their evolutionary history as the group diversified following the end-Cretaceous mass extinction. Subsequent species formation has predominantly been via geographic isolation and sexual selection, process that need not generate new ecologically-related morphological variation. This study contributes to our understanding of biodiversity. Instead of being constrained only by the ecological resources available to support species, diversity may also be limited by the ability or propensity of species to divide up resources. Abstract Whether ecological differences between species evolve in parallel with lineage diversification is a fundamental issue in evolutionary biology. These processes might be connected if conditions that favor the proliferation of species, such as release from competitors, facilitate the evolution of novel ecological relationships. Despite this, phylogenetic studies do not consistently identify such a connection. Conversely, if higher diversity caused species to become increasingly specialized ecologically, lineage diversification might become dissociated from ecological diversification. In this analysis, we ask whether the rate of lineage diversification in a large clade of birds is correlated with morphological specialization and with rates of morphological evolution. We find that morphological variation is related to species richness within clades, but that rates of morphological evolution are decoupled from the rate of lineage diversification. Additionally, morphological specialization within lineages is independent of the rate at which lineages diversify, with the results apparently robust against false negative inference. This dissociation is likely a consequence of the major ecomorphological differences between avian clades arising early in their evolutionary history, with comparatively little variation added subsequently, while avian diversification has been driven predominantly by geographic isolation and sexual selection. Accordingly, biodiversity appears to limited by the extent to which taxa can subdivide exploited regions of ecological space, and not just overall ecological opportunity. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701630 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701630">Read the Article</a></i> </p> --> <p><b>Biodiversity may be limited by division of resources and not just ecological opportunity </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;basic issue in evolutionary biology is the relationship between the rate of species formation and the rate of morphological diversification. We expect these rates to be correlated because conditions that favor an increase in one commonly accelerates the other. For example, a population that colonizes an island lacking competing species may diversify into new ecological roles while splitting into multiple species. Alternatively, rates of speciation and ecological diversification might not be correlated if descendant species become increasingly ecologically specialized in response to growing competition in diverse communities. In this study, researchers gathered morphological data from over 2000 species from 11 orders of predominantly arboreal birds to test whether speciation and morphological diversification are generally correlated. They found that the size, shape, and morphological specialization are unrelated to rate of diversification. They suggest that this is because most of the variation in the group arose early in their evolutionary history as the group diversified following the end-Cretaceous mass extinction. Subsequent species formation has predominantly been via geographic isolation and sexual selection, process that need not generate new ecologically-related morphological variation. This study contributes to our understanding of biodiversity. Instead of being constrained only by the ecological resources available to support species, diversity may also be limited by the ability or propensity of species to divide up resources. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hether ecological differences between species evolve in parallel with lineage diversification is a fundamental issue in evolutionary biology. These processes might be connected if conditions that favor the proliferation of species, such as release from competitors, facilitate the evolution of novel ecological relationships. Despite this, phylogenetic studies do not consistently identify such a connection. Conversely, if higher diversity caused species to become increasingly specialized ecologically, lineage diversification might become dissociated from ecological diversification. In this analysis, we ask whether the rate of lineage diversification in a large clade of birds is correlated with morphological specialization and with rates of morphological evolution. We find that morphological variation is related to species richness within clades, but that rates of morphological evolution are decoupled from the rate of lineage diversification. Additionally, morphological specialization within lineages is independent of the rate at which lineages diversify, with the results apparently robust against false negative inference. This dissociation is likely a consequence of the major ecomorphological differences between avian clades arising early in their evolutionary history, with comparatively little variation added subsequently, while avian diversification has been driven predominantly by geographic isolation and sexual selection. Accordingly, biodiversity appears to limited by the extent to which taxa can subdivide exploited regions of ecological space, and not just overall ecological opportunity. </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, 03 Dec 2018 06:00:00 GMT “Short-sighted evolution constrains the efficacy of long-term bet-hedging” https://amnat.org/an/newpapers/MarLibby-A.html The DOI will be https://dx.doi.org/10.1086/701786 Selection in a fluctuating environment drives bet-hedging strategies that increase the risk of extinction Abstract To survive unpredictable environmental change, many organisms adopt bet-hedging strategies that are initially costly, but provide a long-term fitness benefit. The temporal extent of these deferred fitness benefits determines whether bet-hedging organisms can survive long enough to realize them. In this paper we examine a model of microbial bet-hedging in which there are two paths to extinction: unpredictable environmental change and demographic stochasticity. In temporally-correlated environments these drivers of extinction select for different switching strategies. Rapid phenotype switching ensures survival in the face of unpredictable environmental change while slower switching organisms go extinct. However, when both switching strategies are present in the same population then demographic stochasticity—enforced by a limited population size—leads to extinction of the faster switching organism. As a result, we find a novel form of evolutionary suicide whereby selection in a fluctuating environment can favor bet-hedging strategies that ultimately increase the risk of extinction. Population structures with multiple subpopulations and dispersal can reduce the risk of extinction from unpredictable environmental change and shift the balance so as to facilitate the evolution of slower switching organisms. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701786 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701786">Read the Article</a></i> </p> --> <p><b>Selection in a fluctuating environment drives bet-hedging strategies that increase the risk of extinction </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>o survive unpredictable environmental change, many organisms adopt bet-hedging strategies that are initially costly, but provide a long-term fitness benefit. The temporal extent of these deferred fitness benefits determines whether bet-hedging organisms can survive long enough to realize them. In this paper we examine a model of microbial bet-hedging in which there are two paths to extinction: unpredictable environmental change and demographic stochasticity. In temporally-correlated environments these drivers of extinction select for different switching strategies. Rapid phenotype switching ensures survival in the face of unpredictable environmental change while slower switching organisms go extinct. However, when both switching strategies are present in the same population then demographic stochasticity&mdash;enforced by a limited population size&mdash;leads to extinction of the faster switching organism. As a result, we find a novel form of evolutionary suicide whereby selection in a fluctuating environment can favor bet-hedging strategies that ultimately increase the risk of extinction. Population structures with multiple subpopulations and dispersal can reduce the risk of extinction from unpredictable environmental change and shift the balance so as to facilitate the evolution of slower switching organisms. </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, 03 Dec 2018 06:00:00 GMT “Indirect interactions shape selection in a multi-species foodweb” https://amnat.org/an/newpapers/MarStart.html Read the Article The tangled bank: Species interactions ripple across foodwebs to shape natural selection Life on Earth does not live, die, or evolve in isolation. Instead, all organisms are embedded in an incredibly complex world filled with other species, whose numbers and traits are constantly shifting. All organisms have to navigate the trials and tribulations of this world, yet we are only beginning to understand how the complexity of natural ecological communities translates to the production of evolutionary patterns. How can we understand how constantly changing ecological communities will shape the form, function, and fitness of organisms, ultimately creating patterns of natural selection and evolutionary change? Here, Denon Start, Arthur Weis, and Benjamin Gilbert (University of Toronto, ON, Canada) investigate how species interactions cascade through a foodweb, and how those cascading interactions shape natural selection. They begin by suggesting that traits and abundances determine patterns of species interactions, and that these same quantities shape evolutionary processes. Because of these common currencies (traits and abundances), we should be able to disentangle the relationships between ecological and evolutionary interactions. Start et al. test this line of reasoning by manipulating species interactions in a natural foodweb at the Koffler Scientific Reserve (www.ksr.utoronto.ca). The foodweb is centered on a gall-forming fly, an organism that interacts with its host plant and other herbivores, and is attacked by a community of enemies. Changes to the traits and abundances of the gall-maker and the many interacting species shaped the strength of species interactions, and the resultant patterns of natural selection. Using indirect interactions grounded in units of traits and abundances is a first step in understanding how complex multi-species communities will shape patterns of natural selection, and by extension will facilitate the rapprochement of community ecology and evolutionary biology. Abstract Species do not live, interact, or evolve in isolation, but are instead members of complex ecological communities. In ecological terms, complex multi-species interactions can be understood by considering indirect effects that are mediated by changes in traits and abundances of intermediate species. Interestingly, traits and abundances are also central to our understanding of phenotypic selection, suggesting that indirect effects may be extended to understand evolution in complex communities. Here, we explore indirect ecological effects and their evolutionary corollary in a well-understood foodweb comprising a plant, its herbivores, and enemies that select for opposite defensive phenotypes in one of the herbivores. We show that ecological indirect interactions are mediated by changes to both the traits and abundances of intermediate species, and that these changes ultimately reduce enemy attack and weaken selection. We discuss the generality of the link between indirect effects and selection. We go on to argue that local adaptation and eco-evolutionary feedback may be less likely in complex multi-species foodwebs than in simpler food chains (e.g. coevolution). Overall, considering selection in complex interaction networks can facilitate the rapprochement of community ecology and evolution. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/701785"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701785">Read the Article</a></i> </p> --> <p><b>The tangled bank: Species interactions ripple across foodwebs to shape natural selection </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>ife on Earth does not live, die, or evolve in isolation. Instead, all organisms are embedded in an incredibly complex world filled with other species, whose numbers and traits are constantly shifting. All organisms have to navigate the trials and tribulations of this world, yet we are only beginning to understand how the complexity of natural ecological communities translates to the production of evolutionary patterns. How can we understand how constantly changing ecological communities will shape the form, function, and fitness of organisms, ultimately creating patterns of natural selection and evolutionary change?</p> <p>Here, Denon Start, Arthur Weis, and Benjamin Gilbert (University of Toronto, ON, Canada) investigate how species interactions cascade through a foodweb, and how those cascading interactions shape natural selection. They begin by suggesting that traits and abundances determine patterns of species interactions, and that these same quantities shape evolutionary processes. Because of these common currencies (traits and abundances), we should be able to disentangle the relationships between ecological and evolutionary interactions. </p> <p>Start et al. test this line of reasoning by manipulating species interactions in a natural foodweb at the Koffler Scientific Reserve (<a href="http://ksr.utoronto.ca/">www.ksr.utoronto.ca</a>). The foodweb is centered on a gall-forming fly, an organism that interacts with its host plant and other herbivores, and is attacked by a community of enemies. Changes to the traits and abundances of the gall-maker and the many interacting species shaped the strength of species interactions, and the resultant patterns of natural selection. Using indirect interactions grounded in units of traits and abundances is a first step in understanding how complex multi-species communities will shape patterns of natural selection, and by extension will facilitate the rapprochement of community ecology and evolutionary biology.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>pecies do not live, interact, or evolve in isolation, but are instead members of complex ecological communities. In ecological terms, complex multi-species interactions can be understood by considering indirect effects that are mediated by changes in traits and abundances of intermediate species. Interestingly, traits and abundances are also central to our understanding of phenotypic selection, suggesting that indirect effects may be extended to understand evolution in complex communities. Here, we explore indirect ecological effects and their evolutionary corollary in a well-understood foodweb comprising a plant, its herbivores, and enemies that select for opposite defensive phenotypes in one of the herbivores. We show that ecological indirect interactions are mediated by changes to both the traits and abundances of intermediate species, and that these changes ultimately reduce enemy attack and weaken selection. We discuss the generality of the link between indirect effects and selection. We go on to argue that local adaptation and eco-evolutionary feedback may be less likely in complex multi-species foodwebs than in simpler food chains (e.g. coevolution). Overall, considering selection in complex interaction networks can facilitate the rapprochement of community ecology and evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 03 Dec 2018 06:00:00 GMT “The effect of pollen limitation on the evolution of mating system and seed size in hermaphroditic plants” https://amnat.org/an/newpapers/MarHuang.html Read the Article This study identifies a novel pathway through which pollen limitation selects for reproductive assurance and mixed mating, and provides an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds Pollen limitation of plant reproduction is becoming increasingly common in nature because of factors such as human disturbance, habitat loss or fragmentation, and climate change, which may reduce plant and pollinator abundance. Pollen limitation may increase the optimal seed size in outcrossing plants. Pollen limitation may also promote the evolution of self-fertilization as a mechanism of reproductive assurance. Previous models of self-fertilization assume a constant seed size, and most of them predict that either complete outcrossing or complete selfing should evolve. However, the effect of pollen limitation on the joint evolution of mating system and seed size is not known. Here, Huang and Burd model how mating system and seed size jointly evolve in hermaphroditic plants under pollen limitation. Pollen limitation in their study means that the fraction of ovules fertilized by outcrossed pollen is less than one. However, the fraction of selfed ovules fertilized is always one, meaning that selfed ovules are never pollen limited, which is likely true for autogamy with prior or delayed mode of self-fertilization. The authors also consider two contrasting assumptions about the fraction of ovules fertilized. In the first, this fraction is independent of ovule production, meaning that the number of ovules fertilized by outcrossed pollen increases linearly with ovule production. In the second, this fraction decreases with ovule production, meaning that the number of ovules fertilized by outcrossed pollen increases less rapidly than ovule production. When the fraction of ovules fertilized is independent of ovule production, Huang and Burd find that either complete outcrossing or complete selfing should evolve. When the fraction of ovules fertilized decreases with ovule production, mixed mating may evolve. This is because the marginal fitness returns from resource investment in the production of outcrossing ovules decrease with ovule production, but those from investment in the production of selfed seeds are a constant value. Therefore, as ovules produced for outcrossing reach a certain number, resource investment in outcrossing reproduction and selfed seeds should obtain the same marginal fitness returns, and plants should allocate the remaining resources to the production of selfed seeds. Under mixed mating, to meet the requirement that the marginal fitness returns through resource investment are equal for an outcrossed seed and a selfed seed, outcrossed seeds should be larger than selfed seeds. The model therefore identifies a novel pathway through which pollen limitation selects for reproductive assurance and mixed mating, and provides an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds. Abstract Pollen limitation, when inadequate pollen receipt results in a plant setting fewer seeds and fruits, can reduce plant reproductive success and promote the evolution of self-fertilization as a mechanism of reproductive assurance. However, the effect of pollen limitation on the joint evolution of mating system and seed size is not known. Using an evolutionarily stable strategy (ESS) resource allocation model, we show that where moderate pollen limitation and strong inbreeding depression select for complete outcrossing, pollen limitation should also increase the optimal seed size. In contrast, pollen limitation should not affect the optimal seed size under complete selfing, in which case ovule fertilization is certain. Under intermediate conditions, a mixed mating system evolves if the probability of ovule fertilization declines as more ovules are produced, so that a selfed seed with inbreeding depression provides equal marginal fitness returns to a larger outcrossed seed that may result from pollen limitation. Under mixed mating, outcrossed seeds should be larger than selfed seeds, and pollen limitation should not affect the optimal size of either outcrossed or selfed seeds. Our results identify a novel pathway through which pollen limitation selects for mixed mating, and provide an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/701782"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701782">Read the Article</a></i> </p> --> <p><b>This study identifies a novel pathway through which pollen limitation selects for reproductive assurance and mixed mating, and provides an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds </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;">P</span>ollen limitation of plant reproduction is becoming increasingly common in nature because of factors such as human disturbance, habitat loss or fragmentation, and climate change, which may reduce plant and pollinator abundance. Pollen limitation may increase the optimal seed size in outcrossing plants. Pollen limitation may also promote the evolution of self-fertilization as a mechanism of reproductive assurance. Previous models of self-fertilization assume a constant seed size, and most of them predict that either complete outcrossing or complete selfing should evolve. However, the effect of pollen limitation on the joint evolution of mating system and seed size is not known.</p> <p>Here, Huang and Burd model how mating system and seed size jointly evolve in hermaphroditic plants under pollen limitation. Pollen limitation in their study means that the fraction of ovules fertilized by outcrossed pollen is less than one. However, the fraction of selfed ovules fertilized is always one, meaning that selfed ovules are never pollen limited, which is likely true for autogamy with prior or delayed mode of self-fertilization. The authors also consider two contrasting assumptions about the fraction of ovules fertilized. In the first, this fraction is independent of ovule production, meaning that the number of ovules fertilized by outcrossed pollen increases linearly with ovule production. In the second, this fraction decreases with ovule production, meaning that the number of ovules fertilized by outcrossed pollen increases less rapidly than ovule production.</p> <p>When the fraction of ovules fertilized is independent of ovule production, Huang and Burd find that either complete outcrossing or complete selfing should evolve. When the fraction of ovules fertilized decreases with ovule production, mixed mating may evolve. This is because the marginal fitness returns from resource investment in the production of outcrossing ovules decrease with ovule production, but those from investment in the production of selfed seeds are a constant value. Therefore, as ovules produced for outcrossing reach a certain number, resource investment in outcrossing reproduction and selfed seeds should obtain the same marginal fitness returns, and plants should allocate the remaining resources to the production of selfed seeds. Under mixed mating, to meet the requirement that the marginal fitness returns through resource investment are equal for an outcrossed seed and a selfed seed, outcrossed seeds should be larger than selfed seeds.</p> <p>The model therefore identifies a novel pathway through which pollen limitation selects for reproductive assurance and mixed mating, and provides an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>ollen limitation, when inadequate pollen receipt results in a plant setting fewer seeds and fruits, can reduce plant reproductive success and promote the evolution of self-fertilization as a mechanism of reproductive assurance. However, the effect of pollen limitation on the joint evolution of mating system and seed size is not known. Using an evolutionarily stable strategy (ESS) resource allocation model, we show that where moderate pollen limitation and strong inbreeding depression select for complete outcrossing, pollen limitation should also increase the optimal seed size. In contrast, pollen limitation should not affect the optimal seed size under complete selfing, in which case ovule fertilization is certain. Under intermediate conditions, a mixed mating system evolves if the probability of ovule fertilization declines as more ovules are produced, so that a selfed seed with inbreeding depression provides equal marginal fitness returns to a larger outcrossed seed that may result from pollen limitation. Under mixed mating, outcrossed seeds should be larger than selfed seeds, and pollen limitation should not affect the optimal size of either outcrossed or selfed seeds. Our results identify a novel pathway through which pollen limitation selects for mixed mating, and provide an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 03 Dec 2018 06:00:00 GMT “Priority effects and non-hierarchical competition shape species composition in a complex grassland community” https://amnat.org/an/newpapers/FebUricchio.html Read the Article Complex outcomes of competition in multispecies communities: priority effects, competitive exclusion, and coexistence The biological world is surprisingly diverse: even in our own backyards, we often see multiple species coexisting despite intense competition for just a few limiting resources like light, water, and nitrogen. Despite a long history of conceptual models to explain how ecological processes like competition or predation determine which species can coexist, it’s still not well understood how these kinds of interactions between species scale up to affect the distribution of species in space and time. It is critical to understand these complex multi-species interactions in a time when human-mediated changes to habitat, climate, and global species distributions are driving rapid environmental changes for many species. Uricchio et al. studied the controls over plant species diversity in California grasslands, an historically widespread and diverse ecosystem. While California grasslands are a reservoir of biodiversity and endemic species, human-caused disturbances, such as grazing and invasions by introduced grasses, have fundamentally altered their composition; in fact, the golden hills of California are gold in large part due to dominance of annual grasses native to Europe. And yet our diverse native grasses persist and coexist with invasive grasses in some regions. What determines the winners and losers in highly diverse ecosystems, like these Mediterranean grasslands? The authors find that the order of arrival of invading species had important consequences for the persistence of native species, since each native grass was more likely to coexist with some exotic species than with others. Their findings also show that the expected outcome of competition between two species can be misleading in complex multi-species communities where indirect competitive interactions are pervasive. California grasslands are just one of many important ecosystems globally that are comprised of highly diverse and complex groups of species. These results suggest that understanding pairwise competitive hierarchies will not be sufficient for predicting long-term ecosystem dynamics. Rather, understanding the order in which species arrive in a given landscape, and their indirect competitive interactions with the species already present there, will ultimately govern which species persist and which fade out due to competition. Abstract Niche and fitness differences control the outcome of competition, but determining their relative importance in invaded communities – which may be far from equilibrium – remains a pressing concern. Moreover, it is unclear whether classic approaches for studying competition, which were developed predominantly for pairs of interacting species, will fully capture dynamics in complex species assemblages. We parameterized a population dynamic model using competition experiments of two native and three exotic species from a grassland community. We found evidence for minimal fitness differences or niche differences between the native species, leading to slow replacement dynamics and priority effects, but large fitness advantages allowed exotics to unconditionally invade natives. Priority effects driven by strong interspecific competition between exotic species drove single-species dominance by one of two exotic species in 80% of model outcomes, while a complex mixture of non-hierarchical competition and coexistence between native and exotic species occurred in the remaining 20%. Fungal infection, a commonly hypothesized coexistence mechanism, had weak fitness effects, and is unlikely to substantially affect coexistence. In contrast to previous work on pairwise outcomes in largely native-dominated communities, our work supports a role for nearly-neutral dynamics and priority effects as drivers of species composition in invaded communities. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/701434">Read the Article</a><!-- <p><i><a href="https://dx.doi.org/10.1086/701434">Read the Article</a></i> </p> --></p> <p><b>Complex outcomes of competition in multispecies communities: priority effects, competitive exclusion, and coexistence </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he biological world is surprisingly diverse: even in our own backyards, we often see multiple species coexisting despite intense competition for just a few limiting resources like light, water, and nitrogen. Despite a long history of conceptual models to explain how ecological processes like competition or predation determine which species can coexist, it’s still not well understood how these kinds of interactions between species scale up to affect the distribution of species in space and time. It is critical to understand these complex multi-species interactions in a time when human-mediated changes to habitat, climate, and global species distributions are driving rapid environmental changes for many species. </p><p>Uricchio et al. studied the controls over plant species diversity in California grasslands, an historically widespread and diverse ecosystem. While California grasslands are a reservoir of biodiversity and endemic species, human-caused disturbances, such as grazing and invasions by introduced grasses, have fundamentally altered their composition; in fact, the golden hills of California are gold in large part due to dominance of annual grasses native to Europe. And yet our diverse native grasses persist and coexist with invasive grasses in some regions. What determines the winners and losers in highly diverse ecosystems, like these Mediterranean grasslands? The authors find that the order of arrival of invading species had important consequences for the persistence of native species, since each native grass was more likely to coexist with some exotic species than with others. Their findings also show that the expected outcome of competition between two species can be misleading in complex multi-species communities where indirect competitive interactions are pervasive. California grasslands are just one of many important ecosystems globally that are comprised of highly diverse and complex groups of species. These results suggest that understanding pairwise competitive hierarchies will not be sufficient for predicting long-term ecosystem dynamics. Rather, understanding the order in which species arrive in a given landscape, and their indirect competitive interactions with the species already present there, will ultimately govern which species persist and which fade out due to competition. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">N</span>iche and fitness differences control the outcome of competition, but determining their relative importance in invaded communities &ndash; which may be far from equilibrium &ndash; remains a pressing concern. Moreover, it is unclear whether classic approaches for studying competition, which were developed predominantly for pairs of interacting species, will fully capture dynamics in complex species assemblages. We parameterized a population dynamic model using competition experiments of two native and three exotic species from a grassland community. We found evidence for minimal fitness differences or niche differences between the native species, leading to slow replacement dynamics and priority effects, but large fitness advantages allowed exotics to unconditionally invade natives. Priority effects driven by strong interspecific competition between exotic species drove single-species dominance by one of two exotic species in 80% of model outcomes, while a complex mixture of non-hierarchical competition and coexistence between native and exotic species occurred in the remaining 20%. Fungal infection, a commonly hypothesized coexistence mechanism, had weak fitness effects, and is unlikely to substantially affect coexistence. In contrast to previous work on pairwise outcomes in largely native-dominated communities, our work supports a role for nearly-neutral dynamics and priority effects as drivers of species composition in invaded communities. </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 Nov 2018 06:00:00 GMT “Predator-prey models with competition: the emergence of territoriality” https://amnat.org/an/newpapers/MarBerestycki.html Read the Article This paper aims at understanding animal territories through a new predator-prey model with strong competition What mechanisms lead certain animals like wolves to form well-separated territories? How are ant territories shaped? And what is the impact of territorial behavior on populations like coyotes? These are some of the questions that Henri Berestycki and Alessandro Zilio consider in a general framework in this article in which they propose a new and concise mathematical model for territoriality. Assuming only that predators and prey interact with the environment and with each other, they emphasize the role played by conspecific competitive behavior, that is between different packs of predators. They find this to be a key factor in the formation of territories. Indeed, strong competition between packs of predators leads to territorial segregation. More precisely, they find that, as the strength of competition becomes large, groups of predators divide the original region into subregions, each of which is occupied by only one group, thus forming territories. This model predicts certain shapes of territories that can be compared with observations. It also relates territory size to other ecological parameters. The findings match observations. By means of their model, the authors also consider the impact of strong competition on other relevant ecological indicators, such as the size of the overall predator population. They derive a rather counterintuitive consequence of strong competition and territoriality: in some situations, predators with territorial behaviors and very aggressive competition can sustain a larger population than identical predators would if they did not adopt a territorial behavior and did not fight. Indeed, the creation of territories leads to prey thriving at the interfaces of these territories that predators tend to avoid. Thus, the model highlights this buffer zone effect by providing a quantitative explanation. Abstract We introduce a model aimed at shedding light on the emergence of territorial behaviors in predators and on the formation of packs. We consider the situation of predators competing for the same prey (or spatially distributed resource). We observe that strong competition between groups of predators leads to the formation of territories. At the edges of territories, prey concentrate and prosper, leading to a feedback loop in the population distribution of predators. We focus our attention on the effects of the segregation of the population of predators into competing, hostile packs on the overall size of the population of predators. We present some numerical simulations that allow us to describe our counter-intuitive and most important conclusion: lethal aggressiveness among hostile groups of predators may actually lead to an increase in their total population. Modèles proie-prédateurs avec compétition&nbsp;: l’émergence de la territorialité Nous introduisons un modèle qui se propose d’apporter un éclairage sur l’émergence de la territorialité et la formation de meutes chez certains prédateurs. Nous considérons des prédateurs en compétition pour la même proie (ou ressource distribuée spatialement). Nous montrons qu’une compétition très forte entre groupes de prédateurs conduit à la formation de territoires. Les proies se concentrent et prospèrent aux interfaces entre territoires, créant ainsi une boucle de rétroaction sur la distribution de la population des prédateurs. Nous étudions plus spécifiquement les effets de la ségrégation des prédateurs entre plusieurs groupes hostiles sur la taille totale de la population de prédateurs. Nous présentons des simulations numériques qui illustrent une de nos conclusions les plus importantes et contre-intuitive&nbsp;: une agressivité létale entre des groupes hostiles de prédateurs peut conduire à un accroissement de la population totale de prédateurs. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/701670"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701670">Read the Article</a></i> </p> --> <p><b>This paper aims at understanding animal territories through a new predator-prey model with strong competition </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hat mechanisms lead certain animals like wolves to form well-separated territories? How are ant territories shaped? And what is the impact of territorial behavior on populations like coyotes? These are some of the questions that Henri Berestycki and Alessandro Zilio consider in a general framework in this article in which they propose a new and concise mathematical model for territoriality. Assuming only that predators and prey interact with the environment and with each other, they emphasize the role played by conspecific competitive behavior, that is between different packs of predators. They find this to be a key factor in the formation of territories. Indeed, strong competition between packs of predators leads to territorial segregation. More precisely, they find that, as the strength of competition becomes large, groups of predators divide the original region into subregions, each of which is occupied by only one group, thus forming territories. This model predicts certain shapes of territories that can be compared with observations. It also relates territory size to other ecological parameters. The findings match observations. By means of their model, the authors also consider the impact of strong competition on other relevant ecological indicators, such as the size of the overall predator population. They derive a rather counterintuitive consequence of strong competition and territoriality: in some situations, predators with territorial behaviors and very aggressive competition can sustain a larger population than identical predators would if they did not adopt a territorial behavior and did not fight. Indeed, the creation of territories leads to prey thriving at the interfaces of these territories that predators tend to avoid. Thus, the model highlights this buffer zone effect by providing a quantitative explanation. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>e introduce a model aimed at shedding light on the emergence of territorial behaviors in predators and on the formation of packs. We consider the situation of predators competing for the same prey (or spatially distributed resource). We observe that strong competition between groups of predators leads to the formation of territories. At the edges of territories, prey concentrate and prosper, leading to a feedback loop in the population distribution of predators. We focus our attention on the effects of the segregation of the population of predators into competing, hostile packs on the overall size of the population of predators. We present some numerical simulations that allow us to describe our counter-intuitive and most important conclusion: lethal aggressiveness among hostile groups of predators may actually lead to an increase in their total population. </p> <h4>Modèles proie-prédateurs avec compétition&nbsp;: l’émergence de la territorialité</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">N</span>ous introduisons un modèle qui se propose d’apporter un éclairage sur l’émergence de la territorialité et la formation de meutes chez certains prédateurs. Nous considérons des prédateurs en compétition pour la même proie (ou ressource distribuée spatialement). Nous montrons qu’une compétition très forte entre groupes de prédateurs conduit à la formation de territoires. Les proies se concentrent et prospèrent aux interfaces entre territoires, créant ainsi une boucle de rétroaction sur la distribution de la population des prédateurs. Nous étudions plus spécifiquement les effets de la ségrégation des prédateurs entre plusieurs groupes hostiles sur la taille totale de la population de prédateurs. Nous présentons des simulations numériques qui illustrent une de nos conclusions les plus importantes et contre-intuitive&nbsp;: une agressivité létale entre des groupes hostiles de prédateurs peut conduire à un accroissement de la population totale de prédateurs.</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 Nov 2018 06:00:00 GMT “Ecological and evolutionary consequences of viral plasticity” https://amnat.org/an/newpapers/MarChoua-A.html The DOI will be https://dx.doi.org/10.1086/701668 Abstract Viruses use the host machinery to replicate and, therefore, their performance depends on the host physiological state. For bacteriophages, this link between host and viral performance has been characterized empirically and with intracellular theories. Such theories are too detailed to be included in models that study host-phage interactions in the long term, which hinders our understanding of systems that range from pathogens infecting gut bacteria to marine phage shaping the oceans. Here, we combined data and models to study the short- and long-term consequences that host physiology has on bacteriophage performance. We compiled data showing the dependence of lytic-phage traits on host growth rate (referred to as viral phenotypic ``plasticity'') to deduce simple expressions that represent such plasticity. Including these expressions in a standard host-phage model allowed us to understand mechanistically how viral plasticity affects emergent evolutionary strategies, and the population dynamics associated with different environmental scenarios including, e.g. nutrient pulses or host starvation. Moreover, we show that plasticity on the offspring number drives the phage ecological and evolutionary dynamics by reinforcing feedbacks between host, virus, and environment. Standard models neglect viral plasticity, which therefore handicaps their predictive ability in realistic scenarios. Our results highlight the importance of viral plasticity to unravel host-phage interactions, and the need of laboratory and field experiments to characterize viral plastic responses across systems. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701668 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701668">Read the Article</a></i> </p> --><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">V</span>iruses use the host machinery to replicate and, therefore, their performance depends on the host physiological state. For bacteriophages, this link between host and viral performance has been characterized empirically and with intracellular theories. Such theories are too detailed to be included in models that study host-phage interactions in the long term, which hinders our understanding of systems that range from pathogens infecting gut bacteria to marine phage shaping the oceans. Here, we combined data and models to study the short- and long-term consequences that host physiology has on bacteriophage performance. We compiled data showing the dependence of lytic-phage traits on host growth rate (referred to as viral phenotypic ``plasticity'') to deduce simple expressions that represent such plasticity. Including these expressions in a standard host-phage model allowed us to understand mechanistically how viral plasticity affects emergent evolutionary strategies, and the population dynamics associated with different environmental scenarios including, e.g. nutrient pulses or host starvation. Moreover, we show that plasticity on the offspring number drives the phage ecological and evolutionary dynamics by reinforcing feedbacks between host, virus, and environment. Standard models neglect viral plasticity, which therefore handicaps their predictive ability in realistic scenarios. Our results highlight the importance of viral plasticity to unravel host-phage interactions, and the need of laboratory and field experiments to characterize viral plastic responses across systems. </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 Nov 2018 06:00:00 GMT “Catastrophic mortality, Allee effects, and marine protected areas” https://amnat.org/an/newpapers/MarAalto-A.html The DOI will be https://dx.doi.org/10.1086/701781 Marine reserves help buffer species with Allee effects against catastrophic mortality events Abstract For many species, reproductive failure may occur if abundance drops below critical ‘Allee’ thresholds for successful breeding, in some cases impeding recovery. At the same time, extreme environmental events can cause catastrophic collapse in otherwise healthy populations. Understanding what natural processes and management strategies may allow for persistence and recovery of natural populations is critical in the face of expected climate change scenarios of increased environmental variability. Using a spatially-explicit continuous-size fishery model with stochastic dispersal, parameterized for abalone – a harvested species with sedentary adults and a dispersing larval phase – we investigated whether the establishment of a system of marine protected areas (MPAs) can prevent population collapse as compared to non-spatial management when populations are affected by mass mortality from environmental shocks and subject to Allee effects. We found that MPA networks dramatically reduced the risk of collapse following catastrophic events (75-90% mortality), while populations often continued to decline in the absence of spatial protection. Similar resilience could be achieved by closing the fishery immediately following mass mortalities but would necessitate long periods without catch and therefore economic income. For species with Allee effects, the use of protected areas can ensure persistence following mass mortality events while maintaining ecosystem services during the recovery period. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701781 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701781">Read the Article</a></i> </p> --> <p><b>Marine reserves help buffer species with Allee effects against catastrophic mortality events </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;">F</span>or many species, reproductive failure may occur if abundance drops below critical ‘Allee’ thresholds for successful breeding, in some cases impeding recovery. At the same time, extreme environmental events can cause catastrophic collapse in otherwise healthy populations. Understanding what natural processes and management strategies may allow for persistence and recovery of natural populations is critical in the face of expected climate change scenarios of increased environmental variability. Using a spatially-explicit continuous-size fishery model with stochastic dispersal, parameterized for abalone – a harvested species with sedentary adults and a dispersing larval phase – we investigated whether the establishment of a system of marine protected areas (MPAs) can prevent population collapse as compared to non-spatial management when populations are affected by mass mortality from environmental shocks and subject to Allee effects. We found that MPA networks dramatically reduced the risk of collapse following catastrophic events (75-90% mortality), while populations often continued to decline in the absence of spatial protection. Similar resilience could be achieved by closing the fishery immediately following mass mortalities but would necessitate long periods without catch and therefore economic income. For species with Allee effects, the use of protected areas can ensure persistence following mass mortality events while maintaining ecosystem services during the recovery period. </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 Nov 2018 06:00:00 GMT “Brood size affects future reproduction in a long-lived bird with precocial young” https://amnat.org/an/newpapers/MarLeach-A.html The DOI will be https://dx.doi.org/10.1086/701783 A female’s brood size affects probability of future nesting, but not survival, in a long-lived bird with precocial young Abstract Estimation of trade-offs between current reproduction and future survival and fecundity of long-lived vertebrates is essential to understanding factors that shape optimal reproductive investment. Black brant geese (Branta bernicla nigricans) fledge more goslings, on average, when their broods are experimentally enlarged to be greater than the most common clutch size of four eggs. Thus, we hypothesized that the lesser frequency of brant clutches exceeding four eggs results, at least partially, from a future reduction in survival, breeding probability, or clutch size for females tending larger broods. We used an eight-year mark-recapture dataset (Barker robust design) with five years of clutch and brood manipulations to estimate long-term consequences of reproductive decisions in brant. We did not find evidence of a trade-off between reproductive effort and true survival or future initiation date and clutch size. Rather, future breeding probability was maximized (0.92 ± 0.03 [se]) for manipulated females tending broods of four goslings and lower for females tending smaller (one gosling; 0.63 ± 0.09 [se]) or larger broods (seven goslings; 0.52 ± 0.15 [se]). Our results suggest that demographic trade-offs for female brant tending large broods may reduce the fitness value of clutches larger than four and, therefore, contribute to the paucity of larger clutches. The lack of a trade-off between reproductive effort and survival provides evidence that survival, to which fitness is most sensitive in long-lived animals, is buffered against temporal variation in brant. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701783 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701783">Read the Article</a></i> </p> --> <p><b>A female’s brood size affects probability of future nesting, but not survival, in a long-lived bird with precocial young </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>stimation of trade-offs between current reproduction and future survival and fecundity of long-lived vertebrates is essential to understanding factors that shape optimal reproductive investment. Black brant geese (<i>Branta bernicla nigricans</i>) fledge more goslings, on average, when their broods are experimentally enlarged to be greater than the most common clutch size of four eggs. Thus, we hypothesized that the lesser frequency of brant clutches exceeding four eggs results, at least partially, from a future reduction in survival, breeding probability, or clutch size for females tending larger broods. We used an eight-year mark-recapture dataset (Barker robust design) with five years of clutch and brood manipulations to estimate long-term consequences of reproductive decisions in brant. We did not find evidence of a trade-off between reproductive effort and true survival or future initiation date and clutch size. Rather, future breeding probability was maximized (0.92 ± 0.03 [se]) for manipulated females tending broods of four goslings and lower for females tending smaller (one gosling; 0.63 ± 0.09 [se]) or larger broods (seven goslings; 0.52 ± 0.15 [se]). Our results suggest that demographic trade-offs for female brant tending large broods may reduce the fitness value of clutches larger than four and, therefore, contribute to the paucity of larger clutches. The lack of a trade-off between reproductive effort and survival provides evidence that survival, to which fitness is most sensitive in long-lived animals, is buffered against temporal variation in brant. </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 Nov 2018 06:00:00 GMT “The evolution of marine larval dispersal kernels in spatially structured habitats: analytical models, individual-based simulations, and comparisons with empirical estimates” https://amnat.org/an/newpapers/MarShaw.html Read the Article How far do baby fish travel away from their parents? Answering this simple question is fairly challenging, and has long been a goal of marine ecology. These ‘dispersal distances’ determine how fish stocks and marine reserves should be managed. Shorter distances would mean that marine reserves should be closer together (so fish can easily move between them) and that fish stocks in distant locations should be managed separately (because fish don’t readily move between them). Longer distances would mean that marine reserves can be farther apart and fish stock populations managed together. Here, researchers Allison Shaw, Cassidy D’Aloia, and Peter Buston take a fresh look at this question, asking what distribution of dispersal distances is expected, based on natural selection in spatially structured habitats. The researchers developed a series of models in different types of environments with edges (where dispersing too far means death), akin to many natural environments such as coral reefs. In models with environments most similar to an actual reef (the Belizean Barrier Reef), they found that most fish disperse short distances and only some travel long distances from their parents. Finally, the researchers compared model results to empirically measured dispersal distances of a coral reef fish from the same region. Model results and empirical results weren’t a perfect match, but they were remarkably similar with both indicating that the majority of fish disperse no more than a kilometer or two from where they were born. If these results withstand scrutiny, then they provide another line of evidence in support of the idea that baby fish may not be dispersing far from their parents. If that’s the case we might need to rethink the spatial scale at which some marine populations are connected and managed. Abstract Understanding the causes of larval dispersal is a major goal of marine ecology, yet most research focuses on proximate causes. Here, we ask how ultimate, evolutionary causes affect dispersal. Building on Hamilton and May’s 1977 classic paper (“Dispersal in stable habitats”), we develop analytic and simulation models for the evolution of dispersal kernels in spatially structured habitats. First, we investigate dispersal in a world without edges and find that most offspring disperse as far as possible, opposite the pattern of empirical data. Adding edges to our model world leads to nearly all offspring dispersing short distances, again a mismatch with empirical data. Adding resource heterogeneity improves our results: most offspring disperse short distances with some dispersing longer distances. Finally, we simulate dispersal evolution in a real seascape in Belize and find that the simulated dispersal kernel and an empirical dispersal kernel from that seascape both have the same shape, with a high level of short-distance dispersal and a low level of long-distance dispersal. The novel contributions of this work are to provide a spatially explicit analytic extension of Hamilton and May 1977, to demonstrate that our spatially explicit simulations and analytic models provide equivalent results, and to use simulation approaches to investigate the evolution of dispersal kernel shape in spatially complex habitats. Our model could be modified in various ways to investigate dispersal evolution in other species and seascapes, providing new insights into patterns of marine larval dispersal. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/701667"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701667">Read the Article</a></i> </p> --><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">H</span>ow far do baby fish travel away from their parents? Answering this simple question is fairly challenging, and has long been a goal of marine ecology. These ‘dispersal distances’ determine how fish stocks and marine reserves should be managed. Shorter distances would mean that marine reserves should be closer together (so fish can easily move between them) and that fish stocks in distant locations should be managed separately (because fish don’t readily move between them). Longer distances would mean that marine reserves can be farther apart and fish stock populations managed together. Here, researchers Allison Shaw, Cassidy D’Aloia, and Peter Buston take a fresh look at this question, asking what distribution of dispersal distances is expected, based on natural selection in spatially structured habitats. The researchers developed a series of models in different types of environments with edges (where dispersing too far means death), akin to many natural environments such as coral reefs. In models with environments most similar to an actual reef (the Belizean Barrier Reef), they found that most fish disperse short distances and only some travel long distances from their parents. Finally, the researchers compared model results to empirically measured dispersal distances of a coral reef fish from the same region. Model results and empirical results weren’t a perfect match, but they were remarkably similar with both indicating that the majority of fish disperse no more than a kilometer or two from where they were born. If these results withstand scrutiny, then they provide another line of evidence in support of the idea that baby fish may not be dispersing far from their parents. If that’s the case we might need to rethink the spatial scale at which some marine populations are connected and managed. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>nderstanding the causes of larval dispersal is a major goal of marine ecology, yet most research focuses on proximate causes. Here, we ask how ultimate, evolutionary causes affect dispersal. Building on Hamilton and May’s 1977 classic paper (“Dispersal in stable habitats”), we develop analytic and simulation models for the evolution of dispersal kernels in spatially structured habitats. First, we investigate dispersal in a world without edges and find that most offspring disperse as far as possible, opposite the pattern of empirical data. Adding edges to our model world leads to nearly all offspring dispersing short distances, again a mismatch with empirical data. Adding resource heterogeneity improves our results: most offspring disperse short distances with some dispersing longer distances. Finally, we simulate dispersal evolution in a real seascape in Belize and find that the simulated dispersal kernel and an empirical dispersal kernel from that seascape both have the same shape, with a high level of short-distance dispersal and a low level of long-distance dispersal. The novel contributions of this work are to provide a spatially explicit analytic extension of Hamilton and May 1977, to demonstrate that our spatially explicit simulations and analytic models provide equivalent results, and to use simulation approaches to investigate the evolution of dispersal kernel shape in spatially complex habitats. Our model could be modified in various ways to investigate dispersal evolution in other species and seascapes, providing new insights into patterns of marine larval dispersal. </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 Nov 2018 06:00:00 GMT “Limiting similarity? The ecological dynamics of natural selection among resources and consumers caused by both apparent and resource competition” https://amnat.org/an/newpapers/AprMcPeek-A.html Read the Article Abstract Much of ecological theory presumes that natural selection should foster species coexistence by phenotypically differentiating competitors so that the stability of the community is increased, but whether this will actually occur is a question of the ecological dynamics of natural selection. I develop an evolutionary model of consumer-resource interactions based on MacArthur’s and Tilman’s classic works, including both resource and apparent competition, to explore what fosters or retards the differentiation of resources and their consumers. Analyses of this model predict that consumers will differentiate only on specific ranges of environmental gradients (e.g., greater productivity, weaker stressors, lower structural complexity); and where it occurs, the magnitude of differentiation also depends on gradient position. In contrast to “limiting similarity” expectations, greater intraspecific phenotypic variance results in less differentiation among the consumers because of how phenotypic variation alters the fitness landscapes driving natural selection. In addition, the final structure of the community that results from the coevolution of these interacting species may be highly contingent on the initial properties of the species as the community is being assembled. These results highlight that evolutionary conclusions about community structure cannot be based on ecological arguments of community stability or coexistence, but rather must be explicitly based on the ecological dynamics of natural selection. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/701629"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701629">Read the Article</a></i> </p> --><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>uch of ecological theory presumes that natural selection should foster species coexistence by phenotypically differentiating competitors so that the stability of the community is increased, but whether this will actually occur is a question of the ecological dynamics of natural selection. I develop an evolutionary model of consumer-resource interactions based on MacArthur’s and Tilman’s classic works, including both resource and apparent competition, to explore what fosters or retards the differentiation of resources and their consumers. Analyses of this model predict that consumers will differentiate only on specific ranges of environmental gradients (e.g., greater productivity, weaker stressors, lower structural complexity); and where it occurs, the magnitude of differentiation also depends on gradient position. In contrast to “limiting similarity” expectations, greater intraspecific phenotypic variance results in less differentiation among the consumers because of how phenotypic variation alters the fitness landscapes driving natural selection. In addition, the final structure of the community that results from the coevolution of these interacting species may be highly contingent on the initial properties of the species as the community is being assembled. These results highlight that evolutionary conclusions about community structure cannot be based on ecological arguments of community stability or coexistence, but rather must be explicitly based on the ecological dynamics of natural selection. </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 Nov 2018 06:00:00 GMT Travel Award for ECR Brazilian Researchers to Attend Evolution 2019 https://amnat.org/announcements/BrazilResearch.html We are pleased to announce a limited-time travel award for students, postdocs, and early-career researchers conducting research in Brazil to attend Evolution 2019 in Providence, RI. This award is made possible by the surplus of funds from the 2015 Evolution meeting in Guaruj&aacute;, Brazil. Applicants must be (1) a current member of SSE, ASN, SSB, or the Sociedade Brasileira de Gen&eacute;tica, (2) conducting research at a university or institution in Brazil, (3) a current graduate student or within 6 years of finishing their PhD, and (4) presenting a talk or poster at Evolution 2019. Apply here by January 15. Clique aqui para a vers&atilde;o em portugu&ecirc;s. &nbsp; &nbsp; <p>We are pleased to announce a limited-time travel award for students, postdocs, and early-career researchers conducting research in Brazil to attend <a href="http://www.evolutionmeetings.org/evolution-2019---providence.html">Evolution 2019 in Providence, RI</a>.</p> <p>This award is made possible by the surplus of funds from the 2015 Evolution meeting in Guaruj&aacute;, Brazil.</p> <p>Applicants must be (1) a current member of SSE, ASN, SSB, or the Sociedade Brasileira de Gen&eacute;tica, (2) conducting research at a university or institution in Brazil, (3) a current graduate student or within 6 years of finishing their PhD, and (4) presenting a talk or poster at Evolution 2019.</p> <p><a href="https://docs.google.com/forms/d/e/1FAIpQLSffOKRucphxym0VSTRpAoxxpv96rtICaUdqrmVQjCtkU5BBHA/viewform">Apply here by January 15.</a></p> <p><a href="https://docs.google.com/forms/d/e/1FAIpQLSdYfpwtF-EbO3McGk_cKJmNazY7RlNEqiflBBXeHu1jGS3NVw/viewform">Clique aqui para a vers&atilde;o em portugu&ecirc;s.</a></p> <p>&nbsp;</p> <p>&nbsp;</p> Mon, 26 Nov 2018 06:00:00 GMT