ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 19 Oct 2018 05:00:00 GMT 60 “Within-host priority effects systematically alter pathogen coexistence” https://amnat.org/an/newpapers/FebClay.html The DOI will be https://dx.doi.org/10.1086/701126 Within-host priority effects foster pathogen coexistence if pathogens benefit from arriving second in coinfections Many organisms are infected with multiple pathogen species at the same time. For instance, many humans are infected with both gut helminths and HIV, malaria, or tuberculosis. These “coinfections” can alter host health, maintain biodiversity, and drive pathogen evolution. However, not all pathogens can coexist within a host population. This is because they are constantly competing for hosts and the resources that hosts contain. One factor that defines how pathogens compete with one another is the order in which they infect hosts. Sometimes, infecting a host first gives a pathogen a competitive advantage over later arriving organisms. Sometimes, infecting an already infected host gives a pathogen an advantage. These “within-host priority effects” are common, but we don’t know how they scale up to alter disease patterns in host populations. Here, Patrick Clay and Volker Rudolf from Rice University, and Kailash Dhir and Meghan Duffy from the University of Michigan teamed up to test whether within-host priority effects can alter pathogen coexistence, using a model system of coinfected zooplankton. In this system, pathogens can be repressed by coinfection if they arrive first in coinfected hosts, and facilitated by coinfection if they arrive second in coinfected hosts. This increases the probability that multiple pathogens can infect populations of zooplankton at once. Their results indicate that within-host priority effects can scale up to alter large scale disease patterns, and should be taken into account when trying to understand and predict multi-pathogen dynamics. Abstract Coinfection of host populations alters pathogen prevalence, host mortality, and pathogen evolution. Because pathogens compete for limiting resources, whether multiple pathogens can coexist in a host population can depend on their within-host interactions which, in turn, can depend on the order in which pathogens infect hosts (within-host priority effects). However, the consequences of within-host priority effects for pathogen coexistence have not been tested. Using laboratory studies with a coinfected zooplankton system, we found that pathogens had increased fitness in coinfected hosts when they were the second pathogen to infect a host, compared to when they were the first pathogen to infect a host. With these results, we parameterized a pathogen coexistence model with priority effects, finding that pathogen coexistence (1) decreased when priority effects increased the fitness of the first pathogen to arrive in coinfected hosts, and (2) increased when priority effects increased the fitness of the second pathogen to arrive in coinfected hosts. We also identified the natural conditions under which we expect within-host priority effects to foster coexistence in our system. These outcomes were the result of positive or negative frequency dependence created by feedback loops between pathogen prevalence and infection order in coinfected hosts. This suggests that priority effects can systematically alter conditions for pathogen coexistence in host populations, thereby changing pathogen community structure and potentially altering host mortality and pathogen evolution via emergent processes. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701126 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701126">Read the Article</a></i> </p> --> <p><b>Within-host priority effects foster pathogen coexistence if pathogens benefit from arriving second in coinfections </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>any organisms are infected with multiple pathogen species at the same time. For instance, many humans are infected with both gut helminths and HIV, malaria, or tuberculosis. These “coinfections” can alter host health, maintain biodiversity, and drive pathogen evolution. However, not all pathogens can coexist within a host population. This is because they are constantly competing for hosts and the resources that hosts contain. One factor that defines how pathogens compete with one another is the order in which they infect hosts. Sometimes, infecting a host first gives a pathogen a competitive advantage over later arriving organisms. Sometimes, infecting an already infected host gives a pathogen an advantage. These “within-host priority effects” are common, but we don’t know how they scale up to alter disease patterns in host populations. </p> <p>Here, Patrick Clay and Volker Rudolf from Rice University, and Kailash Dhir and Meghan Duffy from the University of Michigan teamed up to test whether within-host priority effects can alter pathogen coexistence, using a model system of coinfected zooplankton. In this system, pathogens can be repressed by coinfection if they arrive first in coinfected hosts, and facilitated by coinfection if they arrive second in coinfected hosts. This increases the probability that multiple pathogens can infect populations of zooplankton at once. Their results indicate that within-host priority effects can scale up to alter large scale disease patterns, and should be taken into account when trying to understand and predict multi-pathogen dynamics. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>oinfection of host populations alters pathogen prevalence, host mortality, and pathogen evolution. Because pathogens compete for limiting resources, whether multiple pathogens can coexist in a host population can depend on their within-host interactions which, in turn, can depend on the order in which pathogens infect hosts (within-host priority effects). However, the consequences of within-host priority effects for pathogen coexistence have not been tested. Using laboratory studies with a coinfected zooplankton system, we found that pathogens had increased fitness in coinfected hosts when they were the second pathogen to infect a host, compared to when they were the first pathogen to infect a host. With these results, we parameterized a pathogen coexistence model with priority effects, finding that pathogen coexistence (1) decreased when priority effects increased the fitness of the first pathogen to arrive in coinfected hosts, and (2) increased when priority effects increased the fitness of the second pathogen to arrive in coinfected hosts. We also identified the natural conditions under which we expect within-host priority effects to foster coexistence in our system. These outcomes were the result of positive or negative frequency dependence created by feedback loops between pathogen prevalence and infection order in coinfected hosts. This suggests that priority effects can systematically alter conditions for pathogen coexistence in host populations, thereby changing pathogen community structure and potentially altering host mortality and pathogen evolution via emergent processes. </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, 16 Oct 2018 05:00:00 GMT “The rarity of size-assortative mating in animals: Assessing the evidence with anuran amphibians” https://amnat.org/an/newpapers/FebGreen.html The DOI will be https://dx.doi.org/10.1086/701124 The rarity of size-assortative mating in animals: assessing the evidence with anuran amphibiansOne of the foundations of population genetics and evolutionary theory is the idea that individuals mate at random because if mating is not random, there are consequences. Assortative mating is a particular form of non-random mating in which animals select their mates according to a shared trait, which results in mated individuals resembling each other phenotypically more than expected by chance. This mating selectivity may affect genetic co-variance and gene flow, sexual co-evolution and mate choice, and potentially even lead to reproductive isolation sufficient to pull populations apart to form new species. Consequently, evidence for assortative mating has been widely sought, and found, to such an extent that it looks to be quite common. Is&nbsp;it? In this study, Green exhaustively surveys the scientific literature on size-assortative mating among frogs and toads and presents a comprehensive meta-analysis of the evidence in light of the behavioral ecology of these animals. Frogs and toads are particularly well studied in this regard. Mated pairs are easy to find and measure, large size is reproductively advantageous, and the calling behavior of male “sitters” allows for female choice, which is unlikely among male “scramblers” that instead fight for possession of mates. Green finds considerable publication bias against non-significant results and analytical bias resulting from the inappropriate pooling of samples, which significantly inflates the apparent occurrence and strength of size-assortative mating. Taking these biases into account, Green finds little, if any, credible evidence for size-assortative mating behavior in any anurans. Instead, large-male advantage among scramblers leads to a different pattern, termed “disproportionate” mating, which should have relatively little evolutionary impact. Green’s work redefines the meaning of assortative mating, reassesses the evidence for its occurrence, and resets the terms for studying this evolutionary important principle. Abstract Assortative mating in animals can have substantial evolutionary impact. Numerous reports also make it appear to be pervasive in occurrence. In assortative mating, defined here in behavioral terms, animals select their mates according to a particular shared trait such that mated individuals resemble each other phenotypically more than expected by chance. Body size is a widely studied assortment trait. This is especially relevant for anuran amphibians (frogs and toads), among whom reproductive advantages may accrue to large individuals of both sexes. Anurans also exhibit discrete forms of male mating behavior. Sedentary calling behavior of “sitters” allows for female choice whereas fighting for possession of mates by “scramblers” precludes female choice. Size-assortative mating in anurans, therefore, should be a property of sitters, not scramblers. I used meta-analysis to assess the occurrence of true size-assortative mating in relation to mating behavior and other variables in 282 studies of 68 species of anurans. I found publication bias against reporting non-significant results and analytical bias resulting from pooling of samples collected at different times or places (Simpson’s Paradox). Pooled samples significantly inflated the apparent occurrence and strength of size-assortative mating. Controlling for such biases left little credible evidence for size-assortative mating behavior in any anurans. Instead, large-male advantage among scramblers was associated with a 2&deg; pattern of concomitant non-random mating. In this “disproportionate” mating, neither sex behaves according to mate choice rules that could lead to consistently strong assortment. It should thus have relatively little evolutionary impact compared to true assortative mating. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701124 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701124">Read the Article</a></i> </p> --> <p><b>The rarity of size-assortative mating in animals: assessing the evidence with anuran amphibians</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;">O</span>ne of the foundations of population genetics and evolutionary theory is the idea that individuals mate at random because if mating is not random, there are consequences. Assortative mating is a particular form of non-random mating in which animals select their mates according to a shared trait, which results in mated individuals resembling each other phenotypically more than expected by chance. This mating selectivity may affect genetic co-variance and gene flow, sexual co-evolution and mate choice, and potentially even lead to reproductive isolation sufficient to pull populations apart to form new species. Consequently, evidence for assortative mating has been widely sought, and found, to such an extent that it looks to be quite common. Is&nbsp;it?</p> <p>In this study, Green exhaustively surveys the scientific literature on size-assortative mating among frogs and toads and presents a comprehensive meta-analysis of the evidence in light of the behavioral ecology of these animals. Frogs and toads are particularly well studied in this regard. Mated pairs are easy to find and measure, large size is reproductively advantageous, and the calling behavior of male &ldquo;sitters&rdquo; allows for female choice, which is unlikely among male &ldquo;scramblers&rdquo; that instead fight for possession of mates. Green finds considerable publication bias against non-significant results and analytical bias resulting from the inappropriate pooling of samples, which significantly inflates the apparent occurrence and strength of size-assortative mating. Taking these biases into account, Green finds little, if any, credible evidence for size-assortative mating behavior in any anurans. Instead, large-male advantage among scramblers leads to a different pattern, termed &ldquo;disproportionate&rdquo; mating, which should have relatively little evolutionary impact. Green&rsquo;s work redefines the meaning of assortative mating, reassesses the evidence for its occurrence, and resets the terms for studying this evolutionary important principle.</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>ssortative mating in animals can have substantial evolutionary impact. Numerous reports also make it appear to be pervasive in occurrence. In assortative mating, defined here in behavioral terms, animals select their mates according to a particular shared trait such that mated individuals resemble each other phenotypically more than expected by chance. Body size is a widely studied assortment trait. This is especially relevant for anuran amphibians (frogs and toads), among whom reproductive advantages may accrue to large individuals of both sexes. Anurans also exhibit discrete forms of male mating behavior. Sedentary calling behavior of &ldquo;sitters&rdquo; allows for female choice whereas fighting for possession of mates by &ldquo;scramblers&rdquo; precludes female choice. Size-assortative mating in anurans, therefore, should be a property of sitters, not scramblers. I used meta-analysis to assess the occurrence of true size-assortative mating in relation to mating behavior and other variables in 282 studies of 68 species of anurans. I found publication bias against reporting non-significant results and analytical bias resulting from pooling of samples collected at different times or places (Simpson&rsquo;s Paradox). Pooled samples significantly inflated the apparent occurrence and strength of size-assortative mating. Controlling for such biases left little credible evidence for size-assortative mating behavior in any anurans. Instead, large-male advantage among scramblers was associated with a 2&deg; pattern of concomitant non-random mating. In this &ldquo;disproportionate&rdquo; mating, neither sex behaves according to mate choice rules that could lead to consistently strong assortment. It should thus have relatively little evolutionary impact compared to true assortative mating.</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, 16 Oct 2018 05:00:00 GMT “Mutualists stabilize coexistence of congeneric legumes” https://amnat.org/an/newpapers/FebSiefert-A.html The DOI will be https://dx.doi.org/10.1086/701056 Rhizobial mutualists stabilize coexistence of closely related plant species Abstract Coexistence requires that stabilizing niche differences, which cause species to limit themselves more than others, outweigh relative fitness differences that cause competitive exclusion. Interactions with shared mutualists, which can differentially affect host fitness and change in magnitude with host frequency, can satisfy these conditions for coexistence, yet empirical tests of mutualist effects on relative fitness and stabilizing niche differences are largely lacking within the framework of coexistence theory. Here, we show that N-fixing rhizobial mutualists mediate coexistence in four naturally co-occurring, congeneric legume (Trifolium) species. Using experimental greenhouse communities, we quantified relative fitness and stabilizing niche differences for each species in the presence of rhizobia originating from conspecific or congeneric hosts. Rhizobia stabilized coexistence by increasing self-limitation of Trifolium species grown with rhizobia isolated from conspecifics, thus allowing congeners to increase when rare. Greenhouse-measured invasion growth rates predicted natural, unmanipulated coexistence dynamics of Trifolium species over two years in our field sites. Our results demonstrate that interactions with shared mutualists can stabilize coexistence of closely related species. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701056 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701056">Read the Article</a></i> </p> --> <p><b>Rhizobial mutualists stabilize coexistence of closely related plant species </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>oexistence requires that stabilizing niche differences, which cause species to limit themselves more than others, outweigh relative fitness differences that cause competitive exclusion. Interactions with shared mutualists, which can differentially affect host fitness and change in magnitude with host frequency, can satisfy these conditions for coexistence, yet empirical tests of mutualist effects on relative fitness and stabilizing niche differences are largely lacking within the framework of coexistence theory. Here, we show that N-fixing rhizobial mutualists mediate coexistence in four naturally co-occurring, congeneric legume (<i>Trifolium</i>) species. Using experimental greenhouse communities, we quantified relative fitness and stabilizing niche differences for each species in the presence of rhizobia originating from conspecific or congeneric hosts. Rhizobia stabilized coexistence by increasing self-limitation of <i>Trifolium</i> species grown with rhizobia isolated from conspecifics, thus allowing congeners to increase when rare. Greenhouse-measured invasion growth rates predicted natural, unmanipulated coexistence dynamics of <i>Trifolium</i> species over two years in our field sites. Our results demonstrate that interactions with shared mutualists can stabilize coexistence of closely related species. </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, 16 Oct 2018 05:00:00 GMT “Shifting vital rate correlations alter predicted population responses to increasingly variable environments” https://amnat.org/an/newpapers/MarIles-A.html The DOI will be https://dx.doi.org/10.1086/701043 Vital rate correlations will change as environments become more variable, impacting fitness for short lived species Abstract Time-series of vital rates are often used to construct “environment-blind” stochastic population projections and calculate the elasticity of population growth to increased temporal variance in vital rates. Here, we show that the utility of this widely used demographic tool is greatly limited by shifts in vital rate correlations that occur as environmental drivers become increasingly variable. The direction and magnitude of these shifts are unpredictable without environmentally-explicit models. Shifting vital rate correlations had the largest fitness effects on life histories with short to medium generation times, potentially hampering comparative analyses based on elasticities to vital rate variance for a wide range of species. Shifts in vital rate correlations are likely ubiquitous in increasingly variable environments and further research should empirically evaluate the life histories for which detailed mechanistic relationships between vital rates and environmental drivers are required for making reliable predictions, versus those for which summarized demographic data are sufficient. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701043 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701043">Read the Article</a></i> </p> --> <p><b>Vital rate correlations will change as environments become more variable, impacting fitness for short lived species </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>ime-series of vital rates are often used to construct “environment-blind” stochastic population projections and calculate the elasticity of population growth to increased temporal variance in vital rates. Here, we show that the utility of this widely used demographic tool is greatly limited by shifts in vital rate correlations that occur as environmental drivers become increasingly variable. The direction and magnitude of these shifts are unpredictable without environmentally-explicit models. Shifting vital rate correlations had the largest fitness effects on life histories with short to medium generation times, potentially hampering comparative analyses based on elasticities to vital rate variance for a wide range of species. Shifts in vital rate correlations are likely ubiquitous in increasingly variable environments and further research should empirically evaluate the life histories for which detailed mechanistic relationships between vital rates and environmental drivers are required for making reliable predictions, versus those for which summarized demographic data are sufficient. </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, 16 Oct 2018 05:00:00 GMT “Reconstructing the geography of speciation from contemporary biodiversity data” https://amnat.org/an/newpapers/FebSkeels.html The DOI will be https://dx.doi.org/10.1086/701125 Simulations show speciation leaves trace in ranges and phylogeny. Sympatric common mode in plants and founder in animals The mechanisms underlying the origin of species have been debated since both Darwin and Wallace noted that there may be different potential mechanisms that drive populations to diverge and eventually become new species. Whether geographic barriers, such as the formation of a mountain range, are more important than, for example, resource competition driving ecological divergence in co-occurring populations (such as proposed for Darwin’s finches) has been the focus of an enduring research program. Yet because speciation events have taken place in the past, trying to reconstruct their geographic context relies on secondary information from the observable geographic ranges of species in the present, which may not reflect historical ranges at the time of speciation. To investigate this, Alex Skeels and Marcel Cardillo of the Australian National University developed a simulation model of dynamic range evolution and diversification. This model allowed the authors to modify the major drivers of geographic range movement over evolutionary time across simulated clades, to determine whether we can still detect the signal of the geographic context of speciation from contemporary biodiversity data such as species distributions and phylogeny. The simulation model suggests that the signal of speciation history can be recovered from contemporary data, and used this to infer the speciation history of a number of plant and animal groups. Animal groups, including a number of bird, mammal, reptile, and amphibian clades, showed strong support for a founder model of speciation – where a long-distance dispersal event establishes a new, isolated population that eventually becomes a new species. The speciation history of plants, on the other hand, appeared to be primarily sympatric. These results suggest that there may be distinctly different processes shaping the origin of species across taxonomic groups, and point to different roles of geography and ecology in the speciation process shaping the evolution of biodiversity around the world. Abstract Inferring the geographic mode of speciation could help reveal the evolutionary and ecological mechanisms that underlie the generation of biodiversity. Comparative methods have sought to reconstruct the geographic speciation history of clades using data on phylogeny and species geographic ranges. However, inference from comparative methods has been limited by uncertainty over whether contemporary biodiversity data retain the historic signal of speciation. We constructed a process-based simulation model to determine the influence of speciation mode and post-speciation range evolution on current biodiversity patterns. The simulations suggest that the signal of speciation history remains detectable in species distributions and phylogeny, even when species ranges have evolved substantially through time. We extracted this signal using a combination of summary statistics that had good power to distinguish speciation modes, then used these statistics to infer the speciation history of 30 plant and animal clades. The results point to broad taxonomic patterns in the modes of speciation, with strongest support for founder speciation in mammals and birds, and strongest support for sympatric speciation in plants. Our model and analyses show that broad-scale comparative methods can be a powerful complementary approach to more focused genomic analyses in the study of the patterns and mechanisms of speciation. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701125 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701125">Read the Article</a></i> </p> --> <p><b>Simulations show speciation leaves trace in ranges and phylogeny. Sympatric common mode in plants and founder in animals </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 mechanisms underlying the origin of species have been debated since both Darwin and Wallace noted that there may be different potential mechanisms that drive populations to diverge and eventually become new species. Whether geographic barriers, such as the formation of a mountain range, are more important than, for example, resource competition driving ecological divergence in co-occurring populations (such as proposed for Darwin’s finches) has been the focus of an enduring research program. Yet because speciation events have taken place in the past, trying to reconstruct their geographic context relies on secondary information from the observable geographic ranges of species in the present, which may not reflect historical ranges at the time of speciation. </p> <p>To investigate this, Alex Skeels and Marcel Cardillo of the Australian National University developed a simulation model of dynamic range evolution and diversification. This model allowed the authors to modify the major drivers of geographic range movement over evolutionary time across simulated clades, to determine whether we can still detect the signal of the geographic context of speciation from contemporary biodiversity data such as species distributions and phylogeny. The simulation model suggests that the signal of speciation history can be recovered from contemporary data, and used this to infer the speciation history of a number of plant and animal groups. Animal groups, including a number of bird, mammal, reptile, and amphibian clades, showed strong support for a founder model of speciation – where a long-distance dispersal event establishes a new, isolated population that eventually becomes a new species. The speciation history of plants, on the other hand, appeared to be primarily sympatric. These results suggest that there may be distinctly different processes shaping the origin of species across taxonomic groups, and point to different roles of geography and ecology in the speciation process shaping the evolution of biodiversity 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;">I</span>nferring the geographic mode of speciation could help reveal the evolutionary and ecological mechanisms that underlie the generation of biodiversity. Comparative methods have sought to reconstruct the geographic speciation history of clades using data on phylogeny and species geographic ranges. However, inference from comparative methods has been limited by uncertainty over whether contemporary biodiversity data retain the historic signal of speciation. We constructed a process-based simulation model to determine the influence of speciation mode and post-speciation range evolution on current biodiversity patterns. The simulations suggest that the signal of speciation history remains detectable in species distributions and phylogeny, even when species ranges have evolved substantially through time. We extracted this signal using a combination of summary statistics that had good power to distinguish speciation modes, then used these statistics to infer the speciation history of 30 plant and animal clades. The results point to broad taxonomic patterns in the modes of speciation, with strongest support for founder speciation in mammals and birds, and strongest support for sympatric speciation in plants. Our model and analyses show that broad-scale comparative methods can be a powerful complementary approach to more focused genomic analyses in the study of the patterns and mechanisms of speciation. </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, 16 Oct 2018 05:00:00 GMT “Predator prey games in multiple habitats reveal mixed strategies in diel vertical migration” https://amnat.org/an/newpapers/MarPinti.html The DOI will be https://dx.doi.org/10.1086/701041 Predator prey games in multiple arenas applied to DVM reveals mixed strategies through frequency dependent processes Can we apply economic principles to fish ecology and diel vertical migration? It appears that the way fish and zooplankton behave in the presence of other individuals can be derived from mathematical notions first developed to describe the interactions between several economic players. In a paper appearing in The&nbsp;American Naturalist, two researchers from the Centre for Ocean Life of DTU (Denmark) modeled the optimal habitat selection strategies of plankton and fish in a water column. Their set-up allows both individual prey (zooplankton) and predators (fish) to choose their position at day and at night. This is the first time that a model has investigated the optimal position of both prey and predators in a water column with such a resolution. The model reproduces features of diel vertical migrations that are observed in nature. For example, at low predation pressure, zooplankton remain near the surface whereas a higher predation pressure induces zooplankton migration between the surface (to feed, at night) and the depths (to hide, during daytime). Fish follow a similar route to maximize their food intake. A deeper knowledge of these complex migration processes is necessary as they play a role in global biogeochemical cycles. Zooplankton and fish actively transport carbon to the depths during diel vertical migrations, therefore removing carbon from the surface. The surface being coupled with the atmosphere, this drawdown of carbon helps reducing the atmospheric CO2 concentration. A better understanding of these biological processes will enable scientists to provide better estimates and predictions of atmospheric CO2 concentrations. Abstract Prey and predators continuously react to each other and to their environment, adjusting their behavior to maximize their fitness. In a pelagic environment, organisms can optimize their fitness by performing diel vertical migrations (DVM). We applied a game theoretic approach to investigate the emergent patterns of optimal habitat selection strategies in a multiple habitat arena. Our set-up allows both players to choose their position at day and at night in the water column. The model reproduces features of vertical migrations observed in nature, including residency at depth or at the surface, vertical migrations, mixed strategies and bimodal distributions within a population. The mixed strategies appear as a consequence of frequency-dependent processes and not of any intra-species difference between individuals. The model also reveals a curious feature, where natural selection on individuals can provoke distinct regime shifts and precipitate an irreversible collapse in fitness. In the case presented here, the increasing voracity of the predator triggers a behavioral shift in the prey reducing the fitness of all members of the predator population. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701041 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701041">Read the Article</a></i> </p> --> <p><b>Predator prey games in multiple arenas applied to DVM reveals mixed strategies through frequency dependent processes </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>an we apply economic principles to fish ecology and diel vertical migration? It appears that the way fish and zooplankton behave in the presence of other individuals can be derived from mathematical notions first developed to describe the interactions between several economic players. </p><p>In a paper appearing in <i>The&nbsp;American Naturalist</i>, two researchers from the Centre for Ocean Life of DTU (Denmark) modeled the optimal habitat selection strategies of plankton and fish in a water column. Their set-up allows both individual prey (zooplankton) and predators (fish) to choose their position at day and at night. This is the first time that a model has investigated the optimal position of both prey and predators in a water column with such a resolution. The model reproduces features of diel vertical migrations that are observed in nature. For example, at low predation pressure, zooplankton remain near the surface whereas a higher predation pressure induces zooplankton migration between the surface (to feed, at night) and the depths (to hide, during daytime). Fish follow a similar route to maximize their food intake. </p><p>A deeper knowledge of these complex migration processes is necessary as they play a role in global biogeochemical cycles. Zooplankton and fish actively transport carbon to the depths during diel vertical migrations, therefore removing carbon from the surface. The surface being coupled with the atmosphere, this drawdown of carbon helps reducing the atmospheric CO<span style="font-size:70%; position:relative; bottom:-0.3em;">2</span> concentration. A better understanding of these biological processes will enable scientists to provide better estimates and predictions of atmospheric CO<span style="font-size:70%; position:relative; bottom:-0.3em;">2</span> concentrations. </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>rey and predators continuously react to each other and to their environment, adjusting their behavior to maximize their fitness. In a pelagic environment, organisms can optimize their fitness by performing diel vertical migrations (DVM). We applied a game theoretic approach to investigate the emergent patterns of optimal habitat selection strategies in a multiple habitat arena. Our set-up allows both players to choose their position at day and at night in the water column. The model reproduces features of vertical migrations observed in nature, including residency at depth or at the surface, vertical migrations, mixed strategies and bimodal distributions within a population. The mixed strategies appear as a consequence of frequency-dependent processes and not of any intra-species difference between individuals. The model also reveals a curious feature, where natural selection on individuals can provoke distinct regime shifts and precipitate an irreversible collapse in fitness. In the case presented here, the increasing voracity of the predator triggers a behavioral shift in the prey reducing the fitness of all members of the predator population. </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, 16 Oct 2018 05:00:00 GMT “Evolution of personal and social immunity in the context of parental care” https://amnat.org/an/newpapers/FebZiadie.html The DOI will be https://dx.doi.org/10.1086/701122 Social immunity involves specific genes and pathways reflecting evolution as an interacting phenotype during parenting Offspring clearly benefit from parents providing food, but what if the parents and offspring live in a microbially rich environment? They might also benefit from parents transferring immunity, but how does this evolve? Is it generalized to all immune functions or is it directed to specific immune molecules? Michelle Ziadie, a PhD student in Moore’s laboratory in collaboration with an undergraduate, Felicia Ebot-Ojong, and research scientist, Libby McKinney, investigated this in a burying beetle. They used multiple experiments manipulating social conditions to distinguish between “social immunity” (where parents increase their immune gene expression specifically to help their offspring) and “shared personal immunity (where parents increase immune gene expression for themselves and offspring benefit indirectly). Burying beetles are especially suitable for this as the mother regurgitates predigested carrion to begging babies, and the parents and offspring live together on the dead vertebrate that they consume. Mothers use anal secretions to prevent the carrion from rotting, but given that they also directly feed their babies, there is an opportunity to transfer immunity to the offspring. Of the three genes studied, two influenced social immunity and one was involved in shared personal immunity. The gene involved in shared immunity is an anti-microbial peptide common in insects, defensing. The other two genes are more specialized, with pgrp-sc2 directly provisioned to babies and thaumatin specialized as an anti-fungal that is not found in insects. This suggests that social immunity provided by parents to offspring arises when the parents can provide directed and specialized immune protection. Abstract Social immunity moderates the spread of pathogens in social groups and is especially likely in groups structured by genetic relatedness. The extent to which specific immune pathways are used is unknown. Here, we investigate the expression and social role of three functionally separate immune genes (pgrp-sc2, thaumatin, and defensin) during parental care in the beetle Nicrophorus vespilloides. These genes reside in different immune pathways, allowing us to test if specific components of the immune system are targeted for social immunity. To test for the evolution of specificity we manipulated the influence of social context and timing on gene expression and quantified the covariance of maternal immune gene expression and offspring fitness. Larvae reduced expression of all three genes in the presence of parents. Parental pgrp-sc2 and thaumatin increased during direct parenting, while defensin was upregulated before larvae arrived. Parental expression of pgrp-sc2 and thaumatin responded similarly to experimental manipulation of timing and presence of larvae, which differed from the response of defensin. We found a positive covariance between maternal expression and offspring fitness for pgrp-sc2 and thaumatin, but not defensin. We suggest that social immunity can involve specific genes and pathways, reflecting evolution as an interacting phenotype during parenting. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701122 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701122">Read the Article</a></i> </p> --> <p><b>Social immunity involves specific genes and pathways reflecting evolution as an interacting phenotype during parenting </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>ffspring clearly benefit from parents providing food, but what if the parents and offspring live in a microbially rich environment? They might also benefit from parents transferring immunity, but how does this evolve? Is it generalized to all immune functions or is it directed to specific immune molecules? Michelle Ziadie, a PhD student in Moore’s laboratory in collaboration with an undergraduate, Felicia Ebot-Ojong, and research scientist, Libby McKinney, investigated this in a burying beetle. They used multiple experiments manipulating social conditions to distinguish between “social immunity” (where parents increase their immune gene expression specifically to help their offspring) and “shared personal immunity (where parents increase immune gene expression for themselves and offspring benefit indirectly). Burying beetles are especially suitable for this as the mother regurgitates predigested carrion to begging babies, and the parents and offspring live together on the dead vertebrate that they consume. Mothers use anal secretions to prevent the carrion from rotting, but given that they also directly feed their babies, there is an opportunity to transfer immunity to the offspring. Of the three genes studied, two influenced social immunity and one was involved in shared personal immunity. The gene involved in shared immunity is an anti-microbial peptide common in insects, <i>defensing</i>. The other two genes are more specialized, with <i>pgrp-sc2</i> directly provisioned to babies and <i>thaumatin</i> specialized as an anti-fungal that is not found in insects. This suggests that social immunity provided by parents to offspring arises when the parents can provide directed and specialized immune protection. </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>ocial immunity moderates the spread of pathogens in social groups and is especially likely in groups structured by genetic relatedness. The extent to which specific immune pathways are used is unknown. Here, we investigate the expression and social role of three functionally separate immune genes (<i>pgrp-sc2</i>, <i>thaumatin</i>, and <i>defensin</i>) during parental care in the beetle <i>Nicrophorus vespilloides</i>. These genes reside in different immune pathways, allowing us to test if specific components of the immune system are targeted for social immunity. To test for the evolution of specificity we manipulated the influence of social context and timing on gene expression and quantified the covariance of maternal immune gene expression and offspring fitness. Larvae reduced expression of all three genes in the presence of parents. Parental <i>pgrp-sc2</i> and <i>thaumatin</i> increased during direct parenting, while <i>defensin</i> was upregulated before larvae arrived. Parental expression of <i>pgrp-sc2</i> and <i>thaumatin</i> responded similarly to experimental manipulation of timing and presence of larvae, which differed from the response of <i>defensin</i>. We found a positive covariance between maternal expression and offspring fitness for <i>pgrp-sc2</i> and <i>thaumatin</i>, but not <i>defensin</i>. We suggest that social immunity can involve specific genes and pathways, reflecting evolution as an interacting phenotype during parenting. </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, 16 Oct 2018 05:00:00 GMT “Pheromone-induced accuracy of nestmate recognition in carpenter ants: Simultaneous decrease of Type I and Type II errors” https://amnat.org/an/newpapers/FebRossi.html The DOI will be https://dx.doi.org/10.1086/701123 Adding a new twist to the traditional view of alarm pheromones: formic acid improves nestmate discrimination in ants *These authors contributed equally to this workBeing able to recognize friends and foes is essential for the evolution of sociality. Animals, including humans, cooperate with group-members but usually deter strangers, which represent a potential threat for the society. While humans and other animals often use visual recognition cues or sounds, insects communicate mostly via chemical messages. Ants are among the most ecologically successful social insects and represent the pinnacle of social life. Their colonies are called “eusocial”: the perfect society. Ant sociality is based on cooperation between group-members and on colony closure: the rejection of any individual that does not belong to the colony and that could steal the common colony’s resources. In many ant species, when aliens are detected around the nest, colony guards release formic acid, a toxic chemical weapon that kills foes but also rings the alarm bell for group-members, which rush to attack the source of threat. Natacha Rossi and colleagues performed controlled experiments at the Laboratory of Experimental and Comparative Ethology (University of Paris 13), in collaboration with the CNRS Research Center on Animal Cognition (University Paul Sabatier, Toulouse), to test whether formic acid, besides its immediate alarm effect, modifies the recognition behavior of carpenter ants. They found that, after smelling formic acid, ants improve discrimination accuracy: they increase aggressive behaviors towards strangers, while at the same time decreasing aggressive acts erroneously directed towards group-members. With this novel discovery, the function of alarm signals becomes more comprehensive than previously thought: not only do they provoke immediate alarm behavior and defensive responses, but they can reduce errors in recognition of identity by allowing enhanced discrimination between enemies, which should be deterred, and friends, which should be preserved during a contest. Taking into account the overall effect of alarm signals opens new perspectives for a deeper understanding of recognition systems and decision making in general. Abstract The ecological and evolutionary success of social insects relies on their ability to efficiently discriminate between group members and aliens. Nestmate recognition occurs by phenotype matching, the comparison of the referent (colony) phenotype to the one of an encountered individual. Based on the level of dissimilarity between the two, the discriminator accepts or rejects the target. The tolerated degree of mismatch is predicted by the acceptance threshold model, which assumes adaptive threshold shifts depending on the costs of discrimination errors. Inherent in the model is that rejection (Type I) and acceptance (Type II) errors are reciprocally related: if one type decreases, the other increases. We studied whether alarm pheromones modulate the acceptance threshold. We exposed Camponotus aethiops ants to formic acid and subsequently measured aggression towards nestmates and non-nestmates. Formic acid induced both more non-nestmate rejection and more nestmate acceptance than a control treatment, thus uncovering an unexpected effect of an alarm pheromone on responses to nestmates. Nestmate discrimination accuracy was improved via a decrease of both types of errors, a result that cannot be explained by a shift in the acceptance threshold. We propose that formic acid increases the amount of information available to the ants, thus decreasing the perceived phenotypic overlap between nestmate and non-nestmate recognition cues. This mechanism for improved discrimination reveals a novel function of alarm pheromones in recognition processes and may have far-reaching implications in our understanding of the modus operandi of recognition systems in general. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/701123 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/701123">Read the Article</a></i> </p> --> <p><b>Adding a new twist to the traditional view of alarm pheromones: formic acid improves nestmate discrimination in ants </b></p> <p>*These authors contributed equally to this work</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>eing able to recognize friends and foes is essential for the evolution of sociality. Animals, including humans, cooperate with group-members but usually deter strangers, which represent a potential threat for the society. While humans and other animals often use visual recognition cues or sounds, insects communicate mostly via chemical messages. Ants are among the most ecologically successful social insects and represent the pinnacle of social life. Their colonies are called “eusocial”: the perfect society. Ant sociality is based on cooperation between group-members and on colony closure: the rejection of any individual that does not belong to the colony and that could steal the common colony’s resources. </p><p>In many ant species, when aliens are detected around the nest, colony guards release formic acid, a toxic chemical weapon that kills foes but also rings the alarm bell for group-members, which rush to attack the source of threat. Natacha Rossi and colleagues performed controlled experiments at the Laboratory of Experimental and Comparative Ethology (University of Paris 13), in collaboration with the CNRS Research Center on Animal Cognition (University Paul Sabatier, Toulouse), to test whether formic acid, besides its immediate alarm effect, modifies the recognition behavior of carpenter ants. They found that, after smelling formic acid, ants improve discrimination accuracy: they increase aggressive behaviors towards strangers, while at the same time decreasing aggressive acts erroneously directed towards group-members. </p><p>With this novel discovery, the function of alarm signals becomes more comprehensive than previously thought: not only do they provoke immediate alarm behavior and defensive responses, but they can reduce errors in recognition of identity by allowing enhanced discrimination between enemies, which should be deterred, and friends, which should be preserved during a contest. Taking into account the overall effect of alarm signals opens new perspectives for a deeper understanding of recognition systems and decision making in general.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he ecological and evolutionary success of social insects relies on their ability to efficiently discriminate between group members and aliens. Nestmate recognition occurs by phenotype matching, the comparison of the referent (colony) phenotype to the one of an encountered individual. Based on the level of dissimilarity between the two, the discriminator accepts or rejects the target. The tolerated degree of mismatch is predicted by the acceptance threshold model, which assumes adaptive threshold shifts depending on the costs of discrimination errors. Inherent in the model is that rejection (Type I) and acceptance (Type II) errors are reciprocally related: if one type decreases, the other increases. We studied whether alarm pheromones modulate the acceptance threshold. We exposed <i>Camponotus aethiops</i> ants to formic acid and subsequently measured aggression towards nestmates and non-nestmates. Formic acid induced both more non-nestmate rejection and more nestmate acceptance than a control treatment, thus uncovering an unexpected effect of an alarm pheromone on responses to nestmates. Nestmate discrimination accuracy was improved via a decrease of both types of errors, a result that cannot be explained by a shift in the acceptance threshold. We propose that formic acid increases the amount of information available to the ants, thus decreasing the perceived phenotypic overlap between nestmate and non-nestmate recognition cues. This mechanism for improved discrimination reveals a novel function of alarm pheromones in recognition processes and may have far-reaching implications in our understanding of the <i>modus operandi</i> of recognition systems in general. </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, 12 Oct 2018 05:00:00 GMT The Natural History Miscellany Explained https://amnat.org/announcements/CallNHM.html Good natural history forms the foundation of almost every “broad discipline” within biology. Most of the giant names in each of our fields, and indeed the fields themselves, trace their beginnings back to natural history exploration. Providing a platform for significant natural history discoveries is the goal of Natural History Miscellany (NHM). There are many flavors of natural history, each of which has value in its appropriate context. The American Naturalist’s mission focuses on advancing “understanding of&hellip;broad biological disciplines toward the conceptual unification of the biological sciences”. Natural history studies can play a critical role in this goal, and indeed are a major component in many regular articles in The American Naturalist. NHM are meant to be an outlet for those studies of natural history that are more concise and focused than would fit in a regular article, but that still address the journal’s mission of advancing broad disciplines or the unification thereof. Some of the most exciting natural history offers a measure of “gee-whiz” biology. These are the studies that surprise, or just make the reader think about how cool the natural world is. Someone once described a great NHM to me as the paper you read and then walk down the hall to tell a friend about because it has such a wow factor. To offer a bit more specific insight about what makes a paper a good candidate for NHM, here are some bullet lists: What kind of paper is successful as a Natural History Miscellany? Rigorous quantitative observations that establish a clear pattern in natural populations Studies that illustrate a general phenomenon that is relevant to multiple taxa Tests of broad or a priori hypotheses Observations that support new hypotheses or revisions to existing ones Chance or opportunistic events that inform broad conceptual problems Creative experiments that test proposed explanations for patterns seen in nature What work generally finds a better home elsewhere? Observations of a single or few occurrences of a phenomenon Taxonomically focused discussions Tests of hypotheses that are chiefly relevant to a narrow taxonomic group Confirmations of previously established phenomena in a new species Simple extensions of geographic distributions These lists are not exhaustive, and there are, of course, exceptions and qualifications to each of these generalities.&nbsp; For example, information on range extensions might by synthesized to address other broader conceptual problems with wide appeal. If you, the author, have a vision for why your natural history work is broadly interesting, and think that you can explain that vision, then consider submitting to NHM. In most cases, an editorial review takes place in a few days and you’ll have an answer about whether the work is going out to review quickly. If we think it will find a more welcoming audience at another journal, then we will convey that opinion so as to not tie the work up in the process unnecessarily. Natural history research will continue to play an essential role in our understanding of ecology, evolution, behavior, and organismal biology. As our name implies, you should consider The American Naturalist as the place to publish your best natural history. <p>Good natural history forms the foundation of almost every &ldquo;broad discipline&rdquo; within biology. Most of the giant names in each of our fields, and indeed the fields themselves, trace their beginnings back to natural history exploration. Providing a platform for significant natural history discoveries is the goal of Natural History Miscellany (NHM).</p> <p>There are many flavors of natural history, each of which has value in its appropriate context. <em>The American Naturalist</em>&rsquo;s mission focuses on advancing &ldquo;understanding of&hellip;broad biological disciplines toward the conceptual unification of the biological sciences&rdquo;. Natural history studies can play a critical role in this goal, and indeed are a major component in many regular articles in <em>The American Naturalist</em>. NHM are meant to be an outlet for those studies of natural history that are more concise and focused than would fit in a regular article, but that still address the journal&rsquo;s mission of advancing broad disciplines or the unification thereof.</p> <p>Some of the most exciting natural history offers a measure of &ldquo;gee-whiz&rdquo; biology. These are the studies that surprise, or just make the reader think about how cool the natural world is. Someone once described a great NHM to me as the paper you read and then walk down the hall to tell a friend about because it has such a wow factor.</p> <p>To offer a bit more specific insight about what makes a paper a good candidate for NHM, here are some bullet lists:</p> <p>What kind of paper is successful as a Natural History Miscellany?</p> <ul> <li>Rigorous quantitative observations that establish a clear pattern in natural populations</li> <li>Studies that illustrate a general phenomenon that is relevant to multiple taxa</li> <li>Tests of broad or a priori hypotheses</li> <li>Observations that support new hypotheses or revisions to existing ones</li> <li>Chance or opportunistic events that inform broad conceptual problems</li> <li>Creative experiments that test proposed explanations for patterns seen in nature</li> </ul> <p>What work generally finds a better home elsewhere?</p> <ul> <li>Observations of a single or few occurrences of a phenomenon</li> <li>Taxonomically focused discussions</li> <li>Tests of hypotheses that are chiefly relevant to a narrow taxonomic group</li> <li>Confirmations of previously established phenomena in a new species</li> <li>Simple extensions of geographic distributions</li> </ul> <p>These lists are not exhaustive, and there are, of course, exceptions and qualifications to each of these generalities.&nbsp; For example, information on range extensions might by synthesized to address other broader conceptual problems with wide appeal.</p> <p>If you, the author, have a vision for why your natural history work is broadly interesting, and think that you can explain that vision, then consider submitting to NHM. In most cases, an editorial review takes place in a few days and you&rsquo;ll have an answer about whether the work is going out to review quickly. If we think it will find a more welcoming audience at another journal, then we will convey that opinion so as to not tie the work up in the process unnecessarily.</p> <p>Natural history research will continue to play an essential role in our understanding of ecology, evolution, behavior, and organismal biology. As our name implies, you should consider <em>The American Naturalist</em> as the place to publish your best natural history.</p> Tue, 09 Oct 2018 05:00:00 GMT “Ecological genetic conflict: Genetic architecture can shift the balance between local adaptation and plasticity” https://amnat.org/an/newpapers/JanLeimar.html The DOI will be https://dx.doi.org/10.1086/700719 Ecological genetic conflict influences local adaptation and phenotypic plasticity Many species have phenotypic variants that occur in specific habitats. The sea snails in the illustration are examples of this. The variants are called ecotypes and differ genetically. Often, differing phenotypes are also influenced by local environmental conditions. This is called phenotypic plasticity. In an article appearing in The&nbsp;American Naturalist, Olof Leimar, Sasha Dall, John McNamara, Bram Kuijper, and Peter Hammerstein investigate how important plasticity will be in comparison with genetic local adaptation. The authors are theoretical biologists and use mathematical models to study evolution. They ask whether the position of genes in the genome can influence how strong plasticity and how strong genetic specialization will be. It is known that genes that cause phenotypes to be locally adapted, i.e. suited to a particular habitat, often occur close together in the genome. The authors asked if this is also likely for genes that make an individual plastically sensitive to the local environmental conditions. This question has not been studied before. Surprisingly, the authors found the opposite, that genes evolve more pronounced plasticity if they are unlinked to genes for local adaptation. They hope that this prediction will spur geneticists to investigate the genomics of phenotypic plasticity. Abstract Genetic polymorphism can contribute to local adaptation in heterogeneous habitats, for instance as a single locus with alleles adapted to different habitats. Phenotypic plasticity can also contribute to trait variation across habitats, through developmental responses to habitat-specific cues. We show that the genetic architecture of genetically polymorphic and plasticity loci may influence the balance between local adaptation and phenotypic plasticity. These effects of genetic architecture are instances of ecological genetic conflict. A reduced effective migration rate for genes tightly linked to a genetic polymorphism provides an explanation for the effects, and they can occur both for a single trait and for a syndrome of co-adapted traits. Using individual-based simulations and numerical analysis, we investigate how among-habitat genetic polymorphism and phenotypic plasticity depend on genetic architecture. We also study the evolution of genetic architecture itself, in the form of rates of recombination between genetically polymorphic loci and plasticity loci. Our main result is that for plasticity genes that are unlinked to loci with between-habitat genetic polymorphism, the slope of a reaction norm is steeper in comparison with the slope favored by plasticity genes that are tightly linked to genes for local adaptation. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700719 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700719">Read the Article</a></i> </p> --> <p><b>Ecological genetic conflict influences local adaptation and phenotypic plasticity </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;">M</span>any species have phenotypic variants that occur in specific habitats. The sea snails in the illustration are examples of this. The variants are called ecotypes and differ genetically. Often, differing phenotypes are also influenced by local environmental conditions. This is called phenotypic plasticity. In an article appearing in <i>The&nbsp;American Naturalist</i>, Olof Leimar, Sasha Dall, John McNamara, Bram Kuijper, and Peter Hammerstein investigate how important plasticity will be in comparison with genetic local adaptation. The authors are theoretical biologists and use mathematical models to study evolution. They ask whether the position of genes in the genome can influence how strong plasticity and how strong genetic specialization will be. It is known that genes that cause phenotypes to be locally adapted, i.e. suited to a particular habitat, often occur close together in the genome. The authors asked if this is also likely for genes that make an individual plastically sensitive to the local environmental conditions. This question has not been studied before. Surprisingly, the authors found the opposite, that genes evolve more pronounced plasticity if they are unlinked to genes for local adaptation. They hope that this prediction will spur geneticists to investigate the genomics of phenotypic plasticity.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>enetic polymorphism can contribute to local adaptation in heterogeneous habitats, for instance as a single locus with alleles adapted to different habitats. Phenotypic plasticity can also contribute to trait variation across habitats, through developmental responses to habitat-specific cues. We show that the genetic architecture of genetically polymorphic and plasticity loci may influence the balance between local adaptation and phenotypic plasticity. These effects of genetic architecture are instances of ecological genetic conflict. A reduced effective migration rate for genes tightly linked to a genetic polymorphism provides an explanation for the effects, and they can occur both for a single trait and for a syndrome of co-adapted traits. Using individual-based simulations and numerical analysis, we investigate how among-habitat genetic polymorphism and phenotypic plasticity depend on genetic architecture. We also study the evolution of genetic architecture itself, in the form of rates of recombination between genetically polymorphic loci and plasticity loci. Our main result is that for plasticity genes that are unlinked to loci with between-habitat genetic polymorphism, the slope of a reaction norm is steeper in comparison with the slope favored by plasticity genes that are tightly linked to genes for local adaptation.</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, 09 Oct 2018 05:00:00 GMT “The snail’s charm” https://amnat.org/an/newpapers/FebDonohue.html The DOI will be https://dx.doi.org/10.1086/700960 The American Naturalist celebrated its 150th anniversary in 2017. It was founded as a journal of natural history “in which we shall endeavor to meet the wants of all lovers of nature.” Beginning as a platform to present acute observations of nature in all of its forms, the journal developed into an important vehicle of the “Evolutionary Synthesis”—a major intellectual achievement of the 20th century that integrated the study of evolution, genetics, and ecological context. During the early years of the journal through much of the 20th century, evolutionary theory was developed to explain the history of nature, before humankind existed to alter it—when time was expansive, and uncommon events, though rare, were frequent enough to effect evolutionary change. Today, with the influence of human activity, dispersal patterns are fundamentally altered, genetic variation is locally limiting in small and fragmented populations, and environments are changing so rapidly that time itself seems limited. How can we use this theory that was built to explain the past, and that depends on an excess of chances and time, to address the challenges of the present and the future when chances are fewer and time seems so short? And, does the habit of naturalists to observe, describe, and cultivate a fascination with nature have any place in the urgent, problem-solving agenda of contemporary science? Abstract In 2017, The American Naturalist celebrated its 150th anniversary. It was founded as a journal of natural history, yet it developed into an important vehicle of the Evolutionary Synthesis. During the early years of the journal through much of the 20th century, evolutionary theory was developed to explain the history of nature, before humankind existed to alter it—when time was expansive, and uncommon events, though rare, were frequent enough to effect evolutionary change. Today, with the influence of human activity, dispersal patterns are fundamentally altered, genetic variation is locally limiting in small and fragmented populations, and environments are changing so rapidly that time itself seems limited. How can we use this theory that was built to explain the past, and that depends on an excess of chances and time, to address the challenges of the present and the future when chances are fewer and time seems so short? And, does the habit of naturalists to observe, describe, and cultivate a fascination with nature have any place in contemporary science? More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700960 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700960">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;"><i>T</span>he American Naturalist</i> celebrated its 150th anniversary in 2017. It was founded as a journal of natural history “in which we shall endeavor to meet the wants of all lovers of nature.” Beginning as a platform to present acute observations of nature in all of its forms, the journal developed into an important vehicle of the “Evolutionary Synthesis”—a major intellectual achievement of the 20th century that integrated the study of evolution, genetics, and ecological context. During the early years of the journal through much of the 20th century, evolutionary theory was developed to explain the history of nature, before humankind existed to alter it—when time was expansive, and uncommon events, though rare, were frequent enough to effect evolutionary change. Today, with the influence of human activity, dispersal patterns are fundamentally altered, genetic variation is locally limiting in small and fragmented populations, and environments are changing so rapidly that time itself seems limited. How can we use this theory that was built to explain the past, and that depends on an excess of chances and time, to address the challenges of the present and the future when chances are fewer and time seems so short? And, does the habit of naturalists to observe, describe, and cultivate a fascination with nature have any place in the urgent, problem-solving agenda of contemporary science? </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n 2017, <i>The American Naturalist</i> celebrated its 150th anniversary. It was founded as a journal of natural history, yet it developed into an important vehicle of the Evolutionary Synthesis. During the early years of the journal through much of the 20th century, evolutionary theory was developed to explain the history of nature, before humankind existed to alter it—when time was expansive, and uncommon events, though rare, were frequent enough to effect evolutionary change. Today, with the influence of human activity, dispersal patterns are fundamentally altered, genetic variation is locally limiting in small and fragmented populations, and environments are changing so rapidly that time itself seems limited. How can we use this theory that was built to explain the past, and that depends on an excess of chances and time, to address the challenges of the present and the future when chances are fewer and time seems so short? And, does the habit of naturalists to observe, describe, and cultivate a fascination with nature have any place in contemporary science? </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, 02 Oct 2018 05:00:00 GMT “Assortative mating by an obliquely transmitted local cultural trait promotes genetic divergence: a model” https://amnat.org/an/newpapers/JanYeh.html The DOI will be https://dx.doi.org/10.1086/700958 Learned birdsong may promote genetic divergence in contact zones even when birds are not learning from their parents Many animals copy behaviors from others. For example, passerine birds learn their birdsong, we humans learn languages, and many species across the animal kingdom learn different ways to get food. When these cultural traits are learned accurately, and variation in the behavior leads to different fitness, they can evolve in a way similar to genetic evolution. Some species learn their mate choice signals, preferences, or both. An interesting consequence is that if two populations learn to not mate with each other, they may become two separate species because they no longer interbreed. However, variation in mating success would not affect a trait’s frequency in the next generation if juveniles learn it from unrelated adults (oblique transmission), because unmated individuals can still teach their unattractive cultural trait to unrelated juveniles. This seems to suggest that oblique transmission, which is often how passerine birds learn their songs, blocks out the effect of sexual selection. In this paper, Justin Yeh builds a model to show that despite oblique transmission, sexual selection on cultural traits can still contribute to the formation of new species. Specifically, when two genetically distinct populations come into contact, if the two populations each sing their own preferred song (or speak their own language), the song would help them maintain the genetic distinction. This is because foreign birds that sing an unpopular song are less likely to find mates, and even though they can still teach the song to unrelated juveniles, their foreign genes are less successful. This is true even when the cultural traits are changing over time due to random chance and learning errors. In contrast, because hybrid offspring could have learned their song from any adult, selection against them does not help keep the songs distinct. These results help us understand how culture may have affected the evolutionary history of both birds and humans. Abstract The effect of learned culture (e.g., birdsong dialects and human languages) on genetic divergence is unclear. Previous theoretical research suggests that because oblique learning allows phenotype transmission from individuals with no offspring to an unrelated individual in the next generation, the effect of sexual selection on the learned trait is masked. However, I propose that migration and spatially constrained learning can form statistical associations between cultural and genetic traits, which may allow selection on the cultural traits to indirectly affect the genetic traits. Here, I build a population genetic model that allows such statistical associations to form, and find that sexual selection and divergent selection on the cultural trait can indeed help maintain genetic divergence through such statistical associations, while selection against genetic hybrids does not affect cultural trait divergence. Furthermore, I find that even when the cultural trait changes over time due to drift and mutation, it can still help maintain genetic divergence. These results suggest the role of obliquely transmitted traits in evolution may be underrated, and the lack of one-to-one associations between cultural and genetic traits may not be sufficient to disprove the role of culture in genetic divergence. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700958 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700958">Read the Article</a></i> </p> --> <p><b>Learned birdsong may promote genetic divergence in contact zones even when birds are not learning from their parents </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;">M</span>any animals copy behaviors from others. For example, passerine birds learn their birdsong, we humans learn languages, and many species across the animal kingdom learn different ways to get food. When these cultural traits are learned accurately, and variation in the behavior leads to different fitness, they can evolve in a way similar to genetic evolution.</p> <p>Some species learn their mate choice signals, preferences, or both. An interesting consequence is that if two populations learn to not mate with each other, they may become two separate species because they no longer interbreed. However, variation in mating success would not affect a trait&rsquo;s frequency in the next generation if juveniles learn it from unrelated adults (oblique transmission), because unmated individuals can still teach their unattractive cultural trait to unrelated juveniles. This seems to suggest that oblique transmission, which is often how passerine birds learn their songs, blocks out the effect of sexual selection.</p> <p>In this paper, Justin Yeh builds a model to show that despite oblique transmission, sexual selection on cultural traits can still contribute to the formation of new species. Specifically, when two genetically distinct populations come into contact, if the two populations each sing their own preferred song (or speak their own language), the song would help them maintain the genetic distinction. This is because foreign birds that sing an unpopular song are less likely to find mates, and even though they can still teach the song to unrelated juveniles, their foreign genes are less successful. This is true even when the cultural traits are changing over time due to random chance and learning errors. In contrast, because hybrid offspring could have learned their song from any adult, selection against them does not help keep the songs distinct. These results help us understand how culture may have affected the evolutionary history of both birds and humans.</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;">T</span>he effect of learned culture (e.g., birdsong dialects and human languages) on genetic divergence is unclear. Previous theoretical research suggests that because oblique learning allows phenotype transmission from individuals with no offspring to an unrelated individual in the next generation, the effect of sexual selection on the learned trait is masked. However, I propose that migration and spatially constrained learning can form statistical associations between cultural and genetic traits, which may allow selection on the cultural traits to indirectly affect the genetic traits. Here, I build a population genetic model that allows such statistical associations to form, and find that sexual selection and divergent selection on the cultural trait can indeed help maintain genetic divergence through such statistical associations, while selection against genetic hybrids does not affect cultural trait divergence. Furthermore, I find that even when the cultural trait changes over time due to drift and mutation, it can still help maintain genetic divergence. These results suggest the role of obliquely transmitted traits in evolution may be underrated, and the lack of one-to-one associations between cultural and genetic traits may not be sufficient to disprove the role of culture in genetic divergence.</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, 02 Oct 2018 05:00:00 GMT “Multiple evolutionary routes to monogamy: modeling the coevolution of mating decisions and parental investment” https://amnat.org/an/newpapers/FebJungwirth.html The DOI will be https://dx.doi.org/10.1086/700698 Monogamy is difficult to achieve, and mating and parenting are intimately intertwined Successful sexual reproduction has two components: mating (to produce offspring) and parenting (to ensure offspring survival), and these are typically traded off against one another. Caring for offspring may, e.g., get in the way of finding mates. Why some animals invest heavily in mating (think salmons) while others focus on parenting (think albatrosses) is a question as old as evolutionary biology. In addition, biologists have long tried to explain why in some species both males and females invest in parenting (think penguins), while in others it is mainly one sex (think sea horses or elephant seals). The relative rarity of our own breeding system (monogamous mating with extended parenting by both sexes) has received special attention. The current manuscript shows that monogamy should indeed be rare unless at least one of the following criteria is fulfilled: (i) competition for mates is low, e.g. when populations are very sparse, (ii) individuals can interfere with mating decisions of others, e.g. by aggressively driving away competitors, (iii) accepting polygamy incurs fitness costs, e.g. reducing fecundity or increasing mortality. The models track how parenting co-evolves with mating decisions and predict that egalitarian sharing among the sexes will only be observed under monogamy. Crucially, the mechanism by which monogamy is favoured (i-iii above) influences both how much absolute investment is allocated towards parenting, and how much relative investment each sex is selected to provide. The most skewed sharing occurs among polygamously mated individuals, where polygamy incurs fecundity costs. Abstract The relationships between mating decisions and parental investment are central to evolution, but to date few theoretical treatments of their co-evolution have been developed. Here we adopt a demographically explicit, adaptive dynamics approach to analyze the co-evolution of female mating decisions and parental investment of both sexes in a self-consistent way. Our models predict that where females cannot interfere with one another’s mating decisions, and where they do not differ in their survival- and fecundity prospects, monogamy should be rare, and favored only under harsh environmental conditions, in sparse populations. However, allowing for interference or asymmetries among females leads to selection for monogamy over a much broader range of environments and demographies. Interference by paired, resident females may prevent unmated rivals from joining existing monogamous pairs, thus barring the formation of polygynous groups. Asymmetries between established, primary females and subsequently joining secondary females may increase the relative costs of early polygynous reproduction compared to delayed monogamy for the latter. The models thus highlight different routes by which monogamy may evolve. We further track how parental investment by the sexes co-evolves with female mating decisions, highlighting how sexual conflict over parental investment is both cause and effect of mating behavior. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700698 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700698">Read the Article</a></i> </p> --> <p><b>Monogamy is difficult to achieve, and mating and parenting are intimately intertwined </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>uccessful sexual reproduction has two components: mating (to produce offspring) and parenting (to ensure offspring survival), and these are typically traded off against one another. Caring for offspring may, e.g., get in the way of finding mates. Why some animals invest heavily in mating (think salmons) while others focus on parenting (think albatrosses) is a question as old as evolutionary biology. In addition, biologists have long tried to explain why in some species both males and females invest in parenting (think penguins), while in others it is mainly one sex (think sea horses or elephant seals). The relative rarity of our own breeding system (monogamous mating with extended parenting by both sexes) has received special attention. The current manuscript shows that monogamy should indeed be rare unless at least one of the following criteria is fulfilled: (i) competition for mates is low, e.g. when populations are very sparse, (ii) individuals can interfere with mating decisions of others, e.g. by aggressively driving away competitors, (iii) accepting polygamy incurs fitness costs, e.g. reducing fecundity or increasing mortality. The models track how parenting co-evolves with mating decisions and predict that egalitarian sharing among the sexes will only be observed under monogamy. Crucially, the mechanism by which monogamy is favoured (i-iii above) influences both how much absolute investment is allocated towards parenting, and how much relative investment each sex is selected to provide. The most skewed sharing occurs among polygamously mated individuals, where polygamy incurs fecundity costs. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he relationships between mating decisions and parental investment are central to evolution, but to date few theoretical treatments of their co-evolution have been developed. Here we adopt a demographically explicit, adaptive dynamics approach to analyze the co-evolution of female mating decisions and parental investment of both sexes in a self-consistent way. Our models predict that where females cannot interfere with one another’s mating decisions, and where they do not differ in their survival- and fecundity prospects, monogamy should be rare, and favored only under harsh environmental conditions, in sparse populations. However, allowing for interference or asymmetries among females leads to selection for monogamy over a much broader range of environments and demographies. Interference by paired, resident females may prevent unmated rivals from joining existing monogamous pairs, thus barring the formation of polygynous groups. Asymmetries between established, primary females and subsequently joining secondary females may increase the relative costs of early polygynous reproduction compared to delayed monogamy for the latter. The models thus highlight different routes by which monogamy may evolve. We further track how parental investment by the sexes co-evolves with female mating decisions, highlighting how sexual conflict over parental investment is both cause and effect of mating behavior. </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, 02 Oct 2018 05:00:00 GMT “Drivers of phylogenetic assemblage structure of the Furnariides, a widespread clade of lowland Neotropical birds” https://amnat.org/an/newpapers/FebPintoLedezma.html The DOI will be https://dx.doi.org/10.1086/700696 Historical processes drive the assembly of local communities in the largest continental endemic clade of birds What drives the assembly of species into local communities? The answer to this fundamental biological question remains elusive, in part because causal processes acting at different spatial and temporal scales ultimately combine to determine community assembly. The balance and relative effect of such processes on community assembly, from ecological mechanisms such as biotic interactions over short spatial distances and years to historical mechanisms such as the origination and extinction of species happening within larger regions and over millions of years, is not yet understood. A common approach to evaluate these processes is to compare observed patterns of community structure, including phylogenetic patterns (e.g., degree of species relatedness), to those expected when these processes are ruled out, namely by random assembly under so-called null models. These models focus mainly on ecological processes and do not model historical processes explicitly. A recently developed dynamic null model explicitly considers such historical processes for creating null expectations, thus allowing a clearer disentanglement between ecological and historical processes. Local bird community assembly has traditionally been studied in the light of biotic interactions, with only a few studies considering historical explanations. Focusing on bird assemblages in the Neotropics, the most species-rich region of the world, a group of international scientists, led by Jesús Pinto-Ledezma and Fabricio Villalobos, applied the recent dynamic null model to evaluate the importance of historical processes on local community assembly. They used the infraorder Furnariides, a predominant component of Neotropical avifauna, as a model group, compiling data on 120 local assemblages of these birds and reconstructing nearly all of the relationships among species of this group. With this extensive data set and applying the dynamic null model, they were able to show that the historical processes of speciation, colonization and local extinction are sufficient to explain community assembly of these birds without invoking local biotic interactions. In addition, the influence of such historical processes depends on the habitat where communities are embedded, with clear differences between forest and open habitats. These findings highlight the importance of mechanisms acting at large spatial and temporal scales on the assembly of species-rich groups in highly diverse regions. Abstract Species co-occurrence in local assemblages is shaped by distinct processes at different spatial and temporal scales. Here we focus on historical explanations and examine the phylogenetic structure of local assemblages of the Furnariides clade (Aves: Passeriformes), assessing the influence of diversification rates on the assembly and species co-occurrence within those assemblages. Using 120 local assemblages across Bolivia and Argentina and a nearly complete phylogeny for the clade, we analyzed assemblage phylogenetic structure applying a recently developed model (DAMOCLES) accounting for the historical processes of speciation, colonization and local extinction. We also evaluated how diversification rates determine species co-occurrence. We found that the assembly of Furnariides assemblages can largely be explained by speciation, colonization and local extinction without invoking current local species interactions. Phylogenetic structure of open habitat assemblages mainly showed clustering, characterized by faster rates of colonization and local extinction than in forest habitats, whereas forest habitat assemblages were congruent with the model’s equal rates expectation, thus highlighting the influence of habitat preferences on assembly and co-occurrence patterns. Our results suggest that historical processes are sufficient to explain local assemblage phylogenetic structure, while there is little evidence for species ecological interactions in avian assemblage diversity and composition. Mecanismos de la estructura filogenética de comunidades de Furnariides, un clado ampliamente distribuido de aves Neotropicales La coexistencia de especies en comunidades locales está determinada por distintos procesos a diferentes escalas espaciales y temporales. En este estudio nos enfocamos en explicaciones históricas para examinar la estructura filogenética de comunidades locales del clado Furnariides (Aves: Passeriformes). Usando 120 comunidades locales distribuidas en Bolivia y Argentina y una filogenia casi completa para el clado, analizamos su estructura filogenética usando un modelo reciente (DAMOCLES) que toma en cuenta procesos históricos de especiación, colonización y extinción local. También, evaluamos la influencia de las tasas de diversificación sobre la coexistencia de especies en dichas comunidades. Encontramos que el ensamble de comunidades de Furnariides puede ser explicado principalmente por los procesos históricos de especiación, colonización y extinción local sin invocar procesos ecológicos como las interacciones entre especies. La estructura filogenética de comunidades en hábitats abiertos presentó un patrón de agrupamiento, mientras que las comunidades en hábitats boscosos tendieron a ser congruentes con el modelo de tasas iguales, resaltando la influencia de preferencias de hábitat sobre el ensamble y patrones de coexistencia en comunidades locales. Nuestros resultados sugieren que los procesos históricos son suficientes para explicar la estructura filogenética de comunidades locales, indicando poca evidencia a favor de interacciones ecológicas sobre la diversidad y composición de comunidades de aves Neotropicales. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700696 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700696">Read the Article</a></i> </p> --> <p><b>Historical processes drive the assembly of local communities in the largest continental endemic clade of birds </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hat drives the assembly of species into local communities? The answer to this fundamental biological question remains elusive, in part because causal processes acting at different spatial and temporal scales ultimately combine to determine community assembly. The balance and relative effect of such processes on community assembly, from ecological mechanisms such as biotic interactions over short spatial distances and years to historical mechanisms such as the origination and extinction of species happening within larger regions and over millions of years, is not yet understood. A common approach to evaluate these processes is to compare observed patterns of community structure, including phylogenetic patterns (e.g., degree of species relatedness), to those expected when these processes are ruled out, namely by random assembly under so-called null models. These models focus mainly on ecological processes and do not model historical processes explicitly. A recently developed dynamic null model explicitly considers such historical processes for creating null expectations, thus allowing a clearer disentanglement between ecological and historical processes. </p><p>Local bird community assembly has traditionally been studied in the light of biotic interactions, with only a few studies considering historical explanations. Focusing on bird assemblages in the Neotropics, the most species-rich region of the world, a group of international scientists, led by Jesús Pinto-Ledezma and Fabricio Villalobos, applied the recent dynamic null model to evaluate the importance of historical processes on local community assembly. They used the infraorder Furnariides, a predominant component of Neotropical avifauna, as a model group, compiling data on 120 local assemblages of these birds and reconstructing nearly all of the relationships among species of this group. With this extensive data set and applying the dynamic null model, they were able to show that the historical processes of speciation, colonization and local extinction are sufficient to explain community assembly of these birds without invoking local biotic interactions. In addition, the influence of such historical processes depends on the habitat where communities are embedded, with clear differences between forest and open habitats. These findings highlight the importance of mechanisms acting at large spatial and temporal scales on the assembly of species-rich groups in highly diverse regions. </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 co-occurrence in local assemblages is shaped by distinct processes at different spatial and temporal scales. Here we focus on historical explanations and examine the phylogenetic structure of local assemblages of the Furnariides clade (Aves: Passeriformes), assessing the influence of diversification rates on the assembly and species co-occurrence within those assemblages. Using 120 local assemblages across Bolivia and Argentina and a nearly complete phylogeny for the clade, we analyzed assemblage phylogenetic structure applying a recently developed model (DAMOCLES) accounting for the historical processes of speciation, colonization and local extinction. We also evaluated how diversification rates determine species co-occurrence. We found that the assembly of Furnariides assemblages can largely be explained by speciation, colonization and local extinction without invoking current local species interactions. Phylogenetic structure of open habitat assemblages mainly showed clustering, characterized by faster rates of colonization and local extinction than in forest habitats, whereas forest habitat assemblages were congruent with the model’s equal rates expectation, thus highlighting the influence of habitat preferences on assembly and co-occurrence patterns. Our results suggest that historical processes are sufficient to explain local assemblage phylogenetic structure, while there is little evidence for species ecological interactions in avian assemblage diversity and composition. </p> <h4>Mecanismos de la estructura filogenética de comunidades de Furnariides, un clado ampliamente distribuido de aves Neotropicales</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;">L</span>a coexistencia de especies en comunidades locales está determinada por distintos procesos a diferentes escalas espaciales y temporales. En este estudio nos enfocamos en explicaciones históricas para examinar la estructura filogenética de comunidades locales del clado Furnariides (Aves: Passeriformes). Usando 120 comunidades locales distribuidas en Bolivia y Argentina y una filogenia casi completa para el clado, analizamos su estructura filogenética usando un modelo reciente (DAMOCLES) que toma en cuenta procesos históricos de especiación, colonización y extinción local. También, evaluamos la influencia de las tasas de diversificación sobre la coexistencia de especies en dichas comunidades. Encontramos que el ensamble de comunidades de Furnariides puede ser explicado principalmente por los procesos históricos de especiación, colonización y extinción local sin invocar procesos ecológicos como las interacciones entre especies. La estructura filogenética de comunidades en hábitats abiertos presentó un patrón de agrupamiento, mientras que las comunidades en hábitats boscosos tendieron a ser congruentes con el modelo de tasas iguales, resaltando la influencia de preferencias de hábitat sobre el ensamble y patrones de coexistencia en comunidades locales. Nuestros resultados sugieren que los procesos históricos son suficientes para explicar la estructura filogenética de comunidades locales, indicando poca evidencia a favor de interacciones ecológicas sobre la diversidad y composición de comunidades de aves Neotropicales. </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, 02 Oct 2018 05:00:00 GMT “Divergent uses of ‘parallel evolution’ during the history of The American Naturalist” https://amnat.org/an/newpapers/JanStuart-A.html The DOI will be https://dx.doi.org/10.1086/700718 Abstract The mechanistic link between natural selection and parallel evolution is well established. Natural selection is the only known deterministic process that can regularly overcome chance and historical contingency to generate the evolution of similar characteristics in independent populations inhabiting similar environments. However, the ready inference of natural selection from parallel evolution has been established only relatively recently. Here, I review the use of ‘parallel evolution’ in the first 125 years of The&nbsp;American Naturalist and show that there were other well-accepted definitions of the term through the history of the field. I discuss the legacy of those alternative ideas and how they helped to shape evolution and ecology as we know it today and finish by discussing a geometric use for ‘parallel’ that may reduce terminological confusion. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700718 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700718">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;">T</span>he mechanistic link between natural selection and parallel evolution is well established. Natural selection is the only known deterministic process that can regularly overcome chance and historical contingency to generate the evolution of similar characteristics in independent populations inhabiting similar environments. However, the ready inference of natural selection from parallel evolution has been established only relatively recently. Here, I review the use of &lsquo;parallel evolution&rsquo; in the first 125 years of <i>The&nbsp;American Naturalist</i> and show that there were other well-accepted definitions of the term through the history of the field. I discuss the legacy of those alternative ideas and how they helped to shape evolution and ecology as we know it today and finish by discussing a geometric use for &lsquo;parallel&rsquo; that may reduce terminological confusion.</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, 26 Sep 2018 05:00:00 GMT “The evolutionary consequences of sex-specific selection in variable environments: Four simple models reveal diverse evolutionary outcomes” https://amnat.org/an/newpapers/JanConnallon-A.html The DOI will be https://dx.doi.org/10.1086/700720 What are the evolutionary rules of adaptation in populations with separate sexes? Abstract The evolutionary trajectories of species with separate sexes depend on the effects of genetic variation on female and male traits, as well as the direction and alignment of selection between the sexes. Classical theory has shown that evolution is equally responsive to selection on females and males, with natural selection increasing the product of the average relative fitness of each sex, over time. This simple rule underlies several important predictions regarding the maintenance of genetic variation, the genetic basis of adaptation, and the dynamics of “sexually antagonistic” alleles. Nevertheless, theories of sex-specific selection overwhelmingly focus on evolution in constant environments, and it remains unclear whether they apply under changing conditions. We derived four simple models of sex-specific selection in variable environments, and explored how conditions of population subdivision, the timing of dispersal, sex differences in dispersal, and the nature of environmental change, mediate the evolutionary dynamics of sex-specific adaptation. We find that these dynamics are acutely sensitive to ecological, demographic, and life-history attributes that vary widely among species, with classical predictions breaking down in contexts of environmental heterogeneity. The evolutionary rules governing sex-specific adaptation may therefore differ between species, suggesting new avenues for research on the evolution of sexual dimorphism. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700720 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700720">Read the Article</a></i> </p> --> <p><b>What are the evolutionary rules of adaptation in populations with separate sexes? </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he evolutionary trajectories of species with separate sexes depend on the effects of genetic variation on female and male traits, as well as the direction and alignment of selection between the sexes. Classical theory has shown that evolution is equally responsive to selection on females and males, with natural selection increasing the product of the average relative fitness of each sex, over time. This simple rule underlies several important predictions regarding the maintenance of genetic variation, the genetic basis of adaptation, and the dynamics of “sexually antagonistic” alleles. Nevertheless, theories of sex-specific selection overwhelmingly focus on evolution in constant environments, and it remains unclear whether they apply under changing conditions. We derived four simple models of sex-specific selection in variable environments, and explored how conditions of population subdivision, the timing of dispersal, sex differences in dispersal, and the nature of environmental change, mediate the evolutionary dynamics of sex-specific adaptation. We find that these dynamics are acutely sensitive to ecological, demographic, and life-history attributes that vary widely among species, with classical predictions breaking down in contexts of environmental heterogeneity. The evolutionary rules governing sex-specific adaptation may therefore differ between species, suggesting new avenues for research on the evolution of sexual dimorphism. </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, 26 Sep 2018 05:00:00 GMT “Biophysical modeling of water economy can explain geographic gradient of body size in anurans” https://amnat.org/an/newpapers/JanGouveia.html The DOI will be https://dx.doi.org/10.1086/700833 Gradients of body size in anurans are only a part of a ‘water-economy story’, biophysical model says In the mid-19th century, the German physiologist Karl Bergmann found that warm-blooded animals (birds and mammals) from cold regions should be, on average, larger than their close relatives from tropical regions because being bigger enhances the conservation of body heat. Since then, ecologists and biogeographers have struggled to understand whether such a pattern would ever hold for cold-blooded animals (such as invertebrates, frogs and lizards) and, if so, whether the mechanism proposed by Bergmann would also fit. Recent studies have shown that, for frogs, what matters is the economy of water, and the existence of a variation in size takes place across a gradient of dehydration, not of temperature. Here, by combining mathematical equations of the frogs’ biophysics, physiological experiments, and data from museum collections, a team of researchers from Brazil and Spain has taken a step further in cracking this riddle of geographic gradients of body size among frogs. They have demonstrated that not only is the need to conserve water the main cause of the variation of body size among these animals, but also that this pattern only emerges depending on the combination of current size and the total resistance of the frogs. Total resistance is mainly determined by the skin’s resistance to dehydration. Small and skin-resistant species are more prone to vary geographically in size in response to environmental dryness. Furthermore, their study hints at the existence of a gradient in resistance to dehydration, a pattern never tested or postulated before. In addition to casting light on a much-debated topic in ecology, these findings help to understand the consequences of climate change, which should alter the spatial patterns of aridity, thus imposing different consequences on frogs according to their features related to economy of water. Abstract Geographical gradients of body size express climate-driven constraints on animals, but whether they exist and what causes them in ectotherms remains contentious. For amphibians, the water conservation hypothesis posits that larger bodies reduce evaporative water loss (EWL) along dehydrating gradients. To address this hypothesis mechanistically, we build upon well-established biophysical equations of water exchange in anurans to propose a state-transition model that predicts an increase of either body size or resistance to EWL as alternative specialization along dehydrating gradients. The model predicts that species whose water economy is more sensitive to variation in body size than to variation in resistance to EWL should increase in size in response to increasing potential evapotranspiration (PET). To evaluate the model predictions, we combine physiological measurements of resistance to EWL with geographic data of body size for four different anuran species. Only one species, Dendropsophus minutus, was predicted to exhibit a positive body size–PET relationship. Results were as predicted for all cases, with one species – Boana faber – showing a negative relationship. Based on a mathematical model verified empirically, we show that clines of body size among anurans depend on the current values of those traits and emerge as an advantage for water conservation. Our model offers a compelling mechanistic explanation for the cause and the variation of gradients of body size in anurans. Modelagem biof&iacute;sica de economia de &aacute;gua pode predizer gradiente geogr&aacute;fico de tamanho corporal em anuros Gradientes geogr&aacute;ficos no tamanho corporal expressam restri&ccedil;&otilde;es clim&aacute;ticas sobre os animais, mas a exist&ecirc;ncia e a causa dessas restri&ccedil;&otilde;es permanecem controversas para ectot&eacute;rmicos. Quando aplicada aos anf&iacute;bios, a hip&oacute;tese da conserva&ccedil;&atilde;o de &aacute;gua postula que quanto maior o tamanho corporal, menor &eacute; a perda de &aacute;gua evaporativa (EWL) ao longo de gradientes de desidrata&ccedil;&atilde;o. Para abordar essa hip&oacute;tese mecanisticamente, utilizamos equa&ccedil;&otilde;es biof&iacute;sicas bem estabelecidas de trocas de &aacute;gua em anuros e propomos um modelo de transi&ccedil;&atilde;o de estados que prediz um aumento no tamanho corporal ou na resist&ecirc;ncia &agrave; EWL como especializa&ccedil;&otilde;es alternativas ao longo de gradientes de desidrata&ccedil;&atilde;o. O modelo prediz que as esp&eacute;cies para as quais a economia de &aacute;gua &eacute; mais sens&iacute;vel &agrave; varia&ccedil;&atilde;o no tamanho corporal do que &agrave; varia&ccedil;&atilde;o na resist&ecirc;ncia a EWL deve aumentar em tamanho em resposta a um aumento na evapotranspira&ccedil;&atilde;o potencial (PET). Para avaliar as predi&ccedil;&otilde;es do modelo, combinamos medidas fisiol&oacute;gicas de resist&ecirc;ncia &agrave; EWL com dados geogr&aacute;ficos de tamanho corporal para quatro esp&eacute;cies de anuros. Esperava-se que apenas uma esp&eacute;cie, Dendropsophus minutus, exibiria uma rela&ccedil;&atilde;o positiva entre tamanho corporal e PET. Os resultados foram como preditos para todos os casos, com uma esp&eacute;cie – Boana faber – mostrando uma rela&ccedil;&atilde;o negativa. Baseado em um modelo matem&aacute;tico verificado empiricamente, mostramos que gradientes de tamanho corporal em anuros dependem da combina&ccedil;&atilde;o de tamanho corporal e resist&ecirc;ncia e emergem como uma vantagem para conserva&ccedil;&atilde;o de &aacute;gua. Nosso modelo fornece uma explica&ccedil;&atilde;o mecan&iacute;stica convincente para a causa e a varia&ccedil;&atilde;o de gradientes de tamanho corporal em anuros. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700833 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700833">Read the Article</a></i> </p> --> <p><b>Gradients of body size in anurans are only a part of a &lsquo;water-economy story&rsquo;, biophysical model says </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;">I</span>n the mid-19th century, the German physiologist Karl Bergmann found that warm-blooded animals (birds and mammals) from cold regions should be, on average, larger than their close relatives from tropical regions because being bigger enhances the conservation of body heat. Since then, ecologists and biogeographers have struggled to understand whether such a pattern would ever hold for cold-blooded animals (such as invertebrates, frogs and lizards) and, if so, whether the mechanism proposed by Bergmann would also fit. Recent studies have shown that, for frogs, what matters is the economy of water, and the existence of a variation in size takes place across a gradient of dehydration, not of temperature.</p> <p>Here, by combining mathematical equations of the frogs&rsquo; biophysics, physiological experiments, and data from museum collections, a team of researchers from Brazil and Spain has taken a step further in cracking this riddle of geographic gradients of body size among frogs. They have demonstrated that not only is the need to conserve water the main cause of the variation of body size among these animals, but also that this pattern only emerges depending on the combination of current size and the total resistance of the frogs. Total resistance is mainly determined by the skin&rsquo;s resistance to dehydration. Small and skin-resistant species are more prone to vary geographically in size in response to environmental dryness. Furthermore, their study hints at the existence of a gradient in resistance to dehydration, a pattern never tested or postulated before. In addition to casting light on a much-debated topic in ecology, these findings help to understand the consequences of climate change, which should alter the spatial patterns of aridity, thus imposing different consequences on frogs according to their features related to economy of water.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>eographical gradients of body size express climate-driven constraints on animals, but whether they exist and what causes them in ectotherms remains contentious. For amphibians, the water conservation hypothesis posits that larger bodies reduce evaporative water loss (EWL) along dehydrating gradients. To address this hypothesis mechanistically, we build upon well-established biophysical equations of water exchange in anurans to propose a state-transition model that predicts an increase of either body size or resistance to EWL as alternative specialization along dehydrating gradients. The model predicts that species whose water economy is more sensitive to variation in body size than to variation in resistance to EWL should increase in size in response to increasing potential evapotranspiration (PET). To evaluate the model predictions, we combine physiological measurements of resistance to EWL with geographic data of body size for four different anuran species. Only one species, <i>Dendropsophus minutus</i>, was predicted to exhibit a positive body size&ndash;PET relationship. Results were as predicted for all cases, with one species &ndash; <i>Boana faber</i> &ndash; showing a negative relationship. Based on a mathematical model verified empirically, we show that clines of body size among anurans depend on the current values of those traits and emerge as an advantage for water conservation. Our model offers a compelling mechanistic explanation for the cause and the variation of gradients of body size in anurans.</p> <h4>Modelagem biof&iacute;sica de economia de &aacute;gua pode predizer gradiente geogr&aacute;fico de tamanho corporal em anuros</h4> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>radientes geogr&aacute;ficos no tamanho corporal expressam restri&ccedil;&otilde;es clim&aacute;ticas sobre os animais, mas a exist&ecirc;ncia e a causa dessas restri&ccedil;&otilde;es permanecem controversas para ectot&eacute;rmicos. Quando aplicada aos anf&iacute;bios, a hip&oacute;tese da conserva&ccedil;&atilde;o de &aacute;gua postula que quanto maior o tamanho corporal, menor &eacute; a perda de &aacute;gua evaporativa (EWL) ao longo de gradientes de desidrata&ccedil;&atilde;o. Para abordar essa hip&oacute;tese mecanisticamente, utilizamos equa&ccedil;&otilde;es biof&iacute;sicas bem estabelecidas de trocas de &aacute;gua em anuros e propomos um modelo de transi&ccedil;&atilde;o de estados que prediz um aumento no tamanho corporal ou na resist&ecirc;ncia &agrave; EWL como especializa&ccedil;&otilde;es alternativas ao longo de gradientes de desidrata&ccedil;&atilde;o. O modelo prediz que as esp&eacute;cies para as quais a economia de &aacute;gua &eacute; mais sens&iacute;vel &agrave; varia&ccedil;&atilde;o no tamanho corporal do que &agrave; varia&ccedil;&atilde;o na resist&ecirc;ncia a EWL deve aumentar em tamanho em resposta a um aumento na evapotranspira&ccedil;&atilde;o potencial (PET). Para avaliar as predi&ccedil;&otilde;es do modelo, combinamos medidas fisiol&oacute;gicas de resist&ecirc;ncia &agrave; EWL com dados geogr&aacute;ficos de tamanho corporal para quatro esp&eacute;cies de anuros. Esperava-se que apenas uma esp&eacute;cie, <i>Dendropsophus minutus</i>, exibiria uma rela&ccedil;&atilde;o positiva entre tamanho corporal e PET. Os resultados foram como preditos para todos os casos, com uma esp&eacute;cie &ndash; <i>Boana faber</i> &ndash; mostrando uma rela&ccedil;&atilde;o negativa. Baseado em um modelo matem&aacute;tico verificado empiricamente, mostramos que gradientes de tamanho corporal em anuros dependem da combina&ccedil;&atilde;o de tamanho corporal e resist&ecirc;ncia e emergem como uma vantagem para conserva&ccedil;&atilde;o de &aacute;gua. Nosso modelo fornece uma explica&ccedil;&atilde;o mecan&iacute;stica convincente para a causa e a varia&ccedil;&atilde;o de gradientes de tamanho corporal em anuros.</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, 26 Sep 2018 05:00:00 GMT “Anther rubbing, a new mechanism that actively promotes selfing in plants” https://amnat.org/an/newpapers/JanAbdelaziz.html The DOI will be https://dx.doi.org/10.1086/700875 Anther rubbing, a new movement discovered in plants, promotes prior selfing Most plants have developed mechanisms to prevent self-fertilization and its detrimental effects of inbreeding depression. Traits promoting selfing in plants have been approached mainly from the perspective of a loss of function, or even only considered as a by-product of non-adaptive evolutionary processes. However, the shift from cross-fertilization to selfing has been identified as one of the most frequent evolutionary transitions. Therefore, adaptive mechanisms actively promoting selfing should be usual in the plant kingdom, but, remarkably, they have not been frequently found. In this study, Abdelaziz et al. describe anther rubbing, a mechanism based in autonomous, repeated, and coordinated movements of the stamens over the stigma during flower opening that promotes self-fertilization in a Brassicaceae species. The researchers use time-lapse video and micro-photography to document this novel reproductive mechanism. They also demonstrate experimentally that anther rubbing is sufficient to achieve maximal reproductive output in this plant. This mechanism is different from the known cases of delayed self-pollination because it assures self-pollination even before the flowers will be exposed to the visit of pollinators. This work demonstrates that elaborated mechanisms, including continuous and repeated movements, can evolve in plants to promote self-pollination. Since the evolution of mating systems in plants is a very active research field, this work will establish a new perspective in the study of the evolution of plant diversity and their mating system strategies. Abstract Self-fertilization has recurrently evolved in plants, involving different strategies and traits, often involving loss of attractive functions, collectively known as the selfing syndrome. However, few traits have been described that actively promote self-fertilization. Here we describe a novel mechanism promoting self-fertilization in the Brassicaceae species Erysimum incanum. This mechanism, which we called anther rubbing, consists of autonomous, repeated, and coordinated movements of the stamens over the stigma during flower opening. We have documented anther rubbing by time-lapse videos and experimentally show that it causes self-pollen deposition on stigmas and is sufficient to achieve maximal reproductive output in E.&nbsp;incanum. We predict that these movements should occur in species with limited inbreeding depression, and indeed we find that inbreeding depression in seed production is negligible in this species. While many studies have documented complex floral traits that promote outcrossing, the occurrence of anther rubbing demonstrates that plants can evolve elaborate and under-appreciated adaptations to promote self-fertilization. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700875 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700875">Read the Article</a></i> </p> --> <p><b>Anther rubbing, a new movement discovered in plants, promotes prior selfing </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ost plants have developed mechanisms to prevent self-fertilization and its detrimental effects of inbreeding depression. Traits promoting selfing in plants have been approached mainly from the perspective of a loss of function, or even only considered as a by-product of non-adaptive evolutionary processes. However, the shift from cross-fertilization to selfing has been identified as one of the most frequent evolutionary transitions. Therefore, adaptive mechanisms actively promoting selfing should be usual in the plant kingdom, but, remarkably, they have not been frequently found. </p> <p>In this study, Abdelaziz et al. describe anther rubbing, a mechanism based in autonomous, repeated, and coordinated movements of the stamens over the stigma during flower opening that promotes self-fertilization in a Brassicaceae species. The researchers use time-lapse video and micro-photography to document this novel reproductive mechanism. They also demonstrate experimentally that anther rubbing is sufficient to achieve maximal reproductive output in this plant. This mechanism is different from the known cases of delayed self-pollination because it assures self-pollination even before the flowers will be exposed to the visit of pollinators. This work demonstrates that elaborated mechanisms, including continuous and repeated movements, can evolve in plants to promote self-pollination. Since the evolution of mating systems in plants is a very active research field, this work will establish a new perspective in the study of the evolution of plant diversity and their mating system strategies. </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>elf-fertilization has recurrently evolved in plants, involving different strategies and traits, often involving loss of attractive functions, collectively known as the selfing syndrome. However, few traits have been described that actively promote self-fertilization. Here we describe a novel mechanism promoting self-fertilization in the Brassicaceae species <i>Erysimum incanum</i>. This mechanism, which we called <em>anther rubbing</em>, consists of autonomous, repeated, and coordinated movements of the stamens over the stigma during flower opening. We have documented anther rubbing by time-lapse videos and experimentally show that it causes self-pollen deposition on stigmas and is sufficient to achieve maximal reproductive output in <i>E.&nbsp;incanum</i>. We predict that these movements should occur in species with limited inbreeding depression, and indeed we find that inbreeding depression in seed production is negligible in this species. While many studies have documented complex floral traits that promote outcrossing, the occurrence of anther rubbing demonstrates that plants can evolve elaborate and under-appreciated adaptations to promote self-fertilization. </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, 26 Sep 2018 05:00:00 GMT “Population variation, environmental gradients, and the evolutionary ecology of plant defense against herbivory” https://amnat.org/an/newpapers/JanHahn.html The DOI will be https://dx.doi.org/10.1086/700838 Climate and herbivory drive positive growth-defense correlations in plants Plants have evolved many defensive traits to protect themselves from the damaging effects of herbivory, such as chemical toxins, thorns, or sticky latex. Energy spent on producing defenses presumably comes at a cost to other functions like growth, resulting in a growth-defense tradeoff. These tradeoffs are best documented at the species level, where species either grow fast but have low defenses, or grow slow but produce high levels of defense. The growth-defense paradigm, however, has received less support when comparing different populations of a single species that grow in different resource environments.Researchers at the University of Montana and Cornell University teamed up to test the hypothesis that populations of showy milkweed (Asclepias speciosa) can have higher levels of both growth and defense when they grow in more favorable climates, compared to less favorable sites. To test this hypothesis, the researchers visited milkweed populations across a strong climate gradient in the western USA and measured their growth and defensive traits. Herbivorous beetles increased in abundance and were more damaging to the plants at more favorable locations. Plants were also larger and better defended in the more favorable climates. These results show that climate and herbivores can cause growth and defense to be positively correlated across populations, in opposition to the growth-defense tradeoffs that are commonly found when comparing different species. This study highlights the different patterns of growth and defense that can occur among species vs. among populations of a single species. Abstract A&nbsp;central tenet of plant defense theory is that adaptation to the abiotic environment sets the template for defense strategies, imposing a tradeoff between plant growth and defense. Yet, this tradeoff, commonly found among species occupying divergent resource environments, may not occur across populations of single species. We hypothesized that more favorable climates and higher levels of herbivory would lead to increases in growth and defense across plant populations. We evaluated whether plant growth and defense traits co-varied across 18 populations of showy milkweed (Asclepias speciosa) inhabiting an east-west climate gradient, spanning 25&deg; of longitude. A suite of traits impacting defense (e.g., latex, cardenolides), growth (e.g., size), or both (e.g., SLA, trichomes) were measured in natural populations and in a common garden, allowing us to evaluate plastic and genetically based variation in these traits. In natural populations, herbivore pressure increased towards warmer sites with longer growing seasons. Growth and defense traits showed strong clinal patterns and were positively correlated. In a common garden, clines with climatic origin were only recapitulated for defense traits. Correlations between growth and defense traits were also weaker and more negative in the common garden compared to the natural populations. Thus, our data suggest that climatically favorable sites likely facilitate the evolution of greater defense at minimal costs to growth, likely because of increased resource acquisition. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700838 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700838">Read the Article</a></i> </p> --> <p><b>Climate and herbivory drive positive growth-defense correlations in plants </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>lants have evolved many defensive traits to protect themselves from the damaging effects of herbivory, such as chemical toxins, thorns, or sticky latex. Energy spent on producing defenses presumably comes at a cost to other functions like growth, resulting in a growth-defense tradeoff. These tradeoffs are best documented at the species level, where species either grow fast but have low defenses, or grow slow but produce high levels of defense. The growth-defense paradigm, however, has received less support when comparing different populations of a single species that grow in different resource environments.</p><p>Researchers at the University of Montana and Cornell University teamed up to test the hypothesis that populations of showy milkweed (<i>Asclepias speciosa</i>) can have higher levels of both growth and defense when they grow in more favorable climates, compared to less favorable sites. To test this hypothesis, the researchers visited milkweed populations across a strong climate gradient in the western USA and measured their growth and defensive traits. Herbivorous beetles increased in abundance and were more damaging to the plants at more favorable locations. Plants were also larger and better defended in the more favorable climates. These results show that climate and herbivores can cause growth and defense to be positively correlated across populations, in opposition to the growth-defense tradeoffs that are commonly found when comparing different species. This study highlights the different patterns of growth and defense that can occur among species vs. among populations of a single species. </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>&nbsp;central tenet of plant defense theory is that adaptation to the abiotic environment sets the template for defense strategies, imposing a tradeoff between plant growth and defense. Yet, this tradeoff, commonly found among species occupying divergent resource environments, may not occur across populations of single species. We hypothesized that more favorable climates and higher levels of herbivory would lead to increases in growth and defense across plant populations. We evaluated whether plant growth and defense traits co-varied across 18 populations of showy milkweed (<i>Asclepias speciosa</i>) inhabiting an east-west climate gradient, spanning 25&deg; of longitude. A suite of traits impacting defense (e.g., latex, cardenolides), growth (e.g., size), or both (e.g., SLA, trichomes) were measured in natural populations and in a common garden, allowing us to evaluate plastic and genetically based variation in these traits. In natural populations, herbivore pressure increased towards warmer sites with longer growing seasons. Growth and defense traits showed strong clinal patterns and were positively correlated. In a common garden, clines with climatic origin were only recapitulated for defense traits. Correlations between growth and defense traits were also weaker and more negative in the common garden compared to the natural populations. Thus, our data suggest that climatically favorable sites likely facilitate the evolution of greater defense at minimal costs to growth, likely because of increased resource acquisition.</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, 26 Sep 2018 05:00:00 GMT “Metaecosystem dynamics of marine phytoplankton alters resource use efficiency along stoichiometric gradients” https://amnat.org/an/newpapers/JanGuelzow.html The DOI will be https://dx.doi.org/10.1086/700835 In metaecosystems the stoichiometry of resource supply affects resource use and biomass production of phytoplankton Resources needed for autotroph growth are often distributed heterogeneously in space, which confronts the organisms with imbalanced resource ratios. The imbalance leads to abiotic flows of matter along concentrations gradients, but also interacts with the spatial mobility of organisms, as these can capture resources in different local habitats. These considerations have been well established in metaecosystem theory, where however theoretical advances occur at much larger speed than empirical assessments of the base predictions. Therefore, we conducted a metaecosystem experiment with marine phytoplankton species. Each metaecosystem consisted of five linearly connected Erlenmeyer flasks (local patches) connected by silicon tubes, which could be opened or closed in different time intervals. Thereby, we created two levels of connectivity (low and high) and crossed this with a second treatment altering resource heterogeneity in space: half of the metaecosystems had equal resource supply in each patch (“uniform”), the other received the same total amount of two nutrients (nitrogen and phosphorus, N and P) but N supplied only to patch 1 and P only supplied to patch 5 (“gradient”). Using this approach we found that nutrients were less efficiently used in the gradient metaecosystem than in the uniform ones. Moreover, at extremely low P supply in the gradient, the abundant N was not efficiently transferred into biomass production anymore. Thus, the stoichiometry of resource supply created a clear spatial imprint on algal productivity – and also composition. Abstract Metaecosystem theory addresses the link between local (within habitats) and regional (between habitats) dynamics by simultaneously analyzing spatial community ecology and abiotic matter flow. Here, we experimentally address how spatial resource gradients and connectivity affect resource use efficiency (RUE) and stoichiometry in marine phytoplankton as well as the community composition at local and regional scales. We created gradostat metaecosystems consisting of five linearly interconnected patches, which either were arranged in countercurrent gradients of nitrogen (N) and phosphorus (P) supply or with a uniform spatial distribution of nutrients, and which had either low or high connectivity. Gradient metaecosystems were characterized by higher remaining N and P concentrations (and N:P ratios) than uniform ones, a difference reduced by higher connectivity. The position of the patch in the gradient strongly constrained elemental stoichiometry, local biovolume production and RUE. Expectedly, algal C:N, biovolume and N-specific RUE decreased towards the N-rich end of gradient metaecosystem, whereas the opposite was observed for most of the gradient for C:P, N:P and P-specific RUE. However, at highest N:P supply, unexpectedly low C:P, N:P, and P-specific RUE values were found, indicating that the low availability of P inhibited efficient use of N and biovolume production. Consequently, gradient metaecosystems had lower overall biovolume at the regional scale. Whereas treatment effects on local richness were weak, gradients were characterized by higher dissimilarity in species composition. Thus, the stoichiometry of resource supply and spatial connectivity between patches appeared as decisive elements constraining phytoplankton composition and functioning in metaecosystems. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700835 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700835">Read the Article</a></i> </p> --> <p><b>In metaecosystems the stoichiometry of resource supply affects resource use and biomass production of phytoplankton </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;">R</span>esources needed for autotroph growth are often distributed heterogeneously in space, which confronts the organisms with imbalanced resource ratios. The imbalance leads to abiotic flows of matter along concentrations gradients, but also interacts with the spatial mobility of organisms, as these can capture resources in different local habitats. These considerations have been well established in metaecosystem theory, where however theoretical advances occur at much larger speed than empirical assessments of the base predictions. Therefore, we conducted a metaecosystem experiment with marine phytoplankton species. Each metaecosystem consisted of five linearly connected Erlenmeyer flasks (local patches) connected by silicon tubes, which could be opened or closed in different time intervals. Thereby, we created two levels of connectivity (low and high) and crossed this with a second treatment altering resource heterogeneity in space: half of the metaecosystems had equal resource supply in each patch (“uniform”), the other received the same total amount of two nutrients (nitrogen and phosphorus, N and P) but N supplied only to patch 1 and P only supplied to patch 5 (“gradient”). Using this approach we found that nutrients were less efficiently used in the gradient metaecosystem than in the uniform ones. Moreover, at extremely low P supply in the gradient, the abundant N was not efficiently transferred into biomass production anymore. Thus, the stoichiometry of resource supply created a clear spatial imprint on algal productivity – and also composition. </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>etaecosystem theory addresses the link between local (within habitats) and regional (between habitats) dynamics by simultaneously analyzing spatial community ecology and abiotic matter flow. Here, we experimentally address how spatial resource gradients and connectivity affect resource use efficiency (RUE) and stoichiometry in marine phytoplankton as well as the community composition at local and regional scales. We created gradostat metaecosystems consisting of five linearly interconnected patches, which either were arranged in countercurrent gradients of nitrogen (N) and phosphorus (P) supply or with a uniform spatial distribution of nutrients, and which had either low or high connectivity. Gradient metaecosystems were characterized by higher remaining N and P concentrations (and N:P ratios) than uniform ones, a difference reduced by higher connectivity. The position of the patch in the gradient strongly constrained elemental stoichiometry, local biovolume production and RUE. Expectedly, algal C:N, biovolume and N-specific RUE decreased towards the N-rich end of gradient metaecosystem, whereas the opposite was observed for most of the gradient for C:P, N:P and P-specific RUE. However, at highest N:P supply, unexpectedly low C:P, N:P, and P-specific RUE values were found, indicating that the low availability of P inhibited efficient use of N and biovolume production. Consequently, gradient metaecosystems had lower overall biovolume at the regional scale. Whereas treatment effects on local richness were weak, gradients were characterized by higher dissimilarity in species composition. Thus, the stoichiometry of resource supply and spatial connectivity between patches appeared as decisive elements constraining phytoplankton composition and functioning in metaecosystems. </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, 26 Sep 2018 05:00:00 GMT Call for Symposium Proposals for Evolution 2019 in Providence, Rhode Island https://amnat.org/announcements/CallSympASN2018.html The American Society of Naturalists invites proposals for a special symposium at the 2019 annual joint meeting of the Society for the Study of Evolution, the American Society of Naturalists, and the Society of Systematic Biologists, to be held June 21-25, 2019, in Providence, RI. Proposed symposium topics should support the Society’s goal to advance the conceptual unification of the biological sciences and further knowledge in evolution, ecology, behavior, and organismal biology. Proposals should be synthetic and interdisciplinary, and address important emerging issues in evolution, ecology, or behavior. A budget of $8,000 for travel, registration, and accommodation is provided to help defray expenses. Proposals should include (1) a title; (2) a description of the symposium topic (one page); (3) a list of six speakers, including institutional affiliations, who have agreed to participate in the symposium; (4) a justification for the symposium explaining why the topic and speakers are appropriate for a Society-sponsored symposium (up to one page). Please submit proposals by midnight Eastern Standard Time on November 1, 2018, by email (kmkay@ucsc.edu) as a single pdf attachment, under subject heading: ASN Symposium Proposal: Evolution 2019. Proposals that include women, young investigators, and individuals from underrepresented groups are especially encouraged. The Society’s selection committee will evaluate proposals based on the significance and timeliness of the topic, and on it differing substantively from recent symposia sponsored by the Society. All applicants will be notified of the decision before the end of December. Kathleen M. Kay ASN Symposium Committee Chair Department of Ecology and Evolutionary Biology University of California, Santa Cruz kmkay@ucsc.edu <p>The American Society of Naturalists invites proposals for a special symposium at the 2019 annual joint meeting of the Society for the Study of Evolution, the American Society of Naturalists, and the Society of Systematic Biologists, to be held June 21-25, 2019, in Providence, RI.</p> <p>Proposed symposium topics should support the Society&rsquo;s goal to advance the conceptual unification of the biological sciences and further knowledge in evolution, ecology, behavior, and organismal biology. Proposals should be synthetic and interdisciplinary, and address important emerging issues in evolution, ecology, or behavior. A budget of $8,000 for travel, registration, and accommodation is provided to help defray expenses.</p> <p>Proposals should include (1) a title; (2) a description of the symposium topic (one page); (3) a list of six speakers, including institutional affiliations, who have agreed to participate in the symposium; (4) a justification for the symposium explaining why the topic and speakers are appropriate for a Society-sponsored symposium (up to one page).</p> <p>Please submit proposals by midnight Eastern Standard Time on November 1, 2018, by email (<a href="mailto:kmkay@ucsc.edu?subject=ASN%20Symposium%20Proposal%3A%20Evolution%202019">kmkay@ucsc.edu</a>) as a single pdf attachment, under subject heading: ASN Symposium Proposal: Evolution 2019. Proposals that include women, young investigators, and individuals from underrepresented groups are especially encouraged.</p> <p>The Society&rsquo;s selection committee will evaluate proposals based on the significance and timeliness of the topic, and on it differing substantively from recent symposia sponsored by the Society. All applicants will be notified of the decision before the end of December.</p> <p><br /> Kathleen M. Kay<br /> ASN Symposium Committee Chair<br /> Department of Ecology and Evolutionary Biology<br /> University of California, Santa Cruz<br /> <a href="mailto:kmkay@ucsc.edu?subject=ASN%20Symposium%20Proposal%3A%20Evolution%202019">kmkay@ucsc.edu</a></p> Mon, 17 Sep 2018 05:00:00 GMT “Space use and leadership modify dilution effects on optimal vigilance under food/safety trade-offs” https://amnat.org/an/newpapers/JanPatin.html The DOI will be https://dx.doi.org/10.1086/700566 Decision-making on space use matters! A model of interacting antipredator strategies: vigilance, grouping, and space use Most animals live under predation risk, and adjust their vigilance to the level of risk they perceive. When living in group, individuals benefit from a “dilution” effect, by which their own risk is reduced by the presence of the other group members that could also be targeted by the predator. Many models of evolution of anti-predator behaviours have focused on the interaction between vigilance and group size, and have always suggested that vigilance should decrease with increasing group size. This is commonly observed, but not always. And animals also adjust predation risk by foraging in areas that they perceive as less risky. In a new article appearing in The&nbsp;American Naturalist, Rémi Patin and colleagues propose a model, designed with social species such as primates or equids in mind, to study the interactions between vigilance, group size, and space use. The model assumes that, within groups, a leader takes all space use decisions for the rest of the group made up of followers. In this situation, the relationship between vigilance and group size becomes complex. Vigilance does not always decrease with group size, because the leader may favor using riskier and richer areas over becoming less vigilant. Followers are less vigilant than the leader, because they need to compensate for uncertainties in future foraging opportunities, and die from predation more often. Overall, followers still benefit from group living, but less than the leader. Leaders might gain more by remaining leaders than by becoming followers in a larger group. These results might therefore explain the apparently paradoxical observation made in some species, such as in equids, that a group leader would reject a potential new group member despite the dilution benefit the addition of the new individual would bring. Abstract Dilution of predation risk within groups allows individuals to be less vigilant and forage more while still facing lower risk than if they were alone. How group size influences vigilance when individuals can also adjust their space use, and whether this relationship differs among individuals contributing differently to space use decisions, remain unknown. We present a model-based study on how dilution affects the optimal anti-predator behavior of group members, in groups where all individuals determine their vigilance level, while group leaders also determine space use. We showed that optimal vigilance did not always decrease with group size, as it was sometimes favorable for individuals in larger groups to use riskier patches while remaining vigilant. Followers were also generally less vigilant than leaders. Indeed, followers needed to acquire more resources than leaders as only the latter could decide when to go to richer patches. Followers still benefit from dilution of predation risk compared to solitary individuals. For leaders, keeping their leadership status can be more important than incorporating new group members to increase dilution. We demonstrate that risk dilution impacts both optimal vigilance and space use, with fitness reward being tied to a member’s ability to influence group space use. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700566 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700566">Read the Article</a></i> </p> --> <p><b>Decision-making on space use matters! A model of interacting antipredator strategies: vigilance, grouping, and space use </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ost animals live under predation risk, and adjust their vigilance to the level of risk they perceive. When living in group, individuals benefit from a “dilution” effect, by which their own risk is reduced by the presence of the other group members that could also be targeted by the predator. Many models of evolution of anti-predator behaviours have focused on the interaction between vigilance and group size, and have always suggested that vigilance should decrease with increasing group size. This is commonly observed, but not always. And animals also adjust predation risk by foraging in areas that they perceive as less risky. In a new article appearing in <i>The&nbsp;American Naturalist</i>, Rémi Patin and colleagues propose a model, designed with social species such as primates or equids in mind, to study the interactions between vigilance, group size, and space use. The model assumes that, within groups, a leader takes all space use decisions for the rest of the group made up of followers. In this situation, the relationship between vigilance and group size becomes complex. Vigilance does not always decrease with group size, because the leader may favor using riskier and richer areas over becoming less vigilant. Followers are less vigilant than the leader, because they need to compensate for uncertainties in future foraging opportunities, and die from predation more often. Overall, followers still benefit from group living, but less than the leader. Leaders might gain more by remaining leaders than by becoming followers in a larger group. These results might therefore explain the apparently paradoxical observation made in some species, such as in equids, that a group leader would reject a potential new group member despite the dilution benefit the addition of the new individual would bring. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">D</span>ilution of predation risk within groups allows individuals to be less vigilant and forage more while still facing lower risk than if they were alone. How group size influences vigilance when individuals can also adjust their space use, and whether this relationship differs among individuals contributing differently to space use decisions, remain unknown. We present a model-based study on how dilution affects the optimal anti-predator behavior of group members, in groups where all individuals determine their vigilance level, while group leaders also determine space use. We showed that optimal vigilance did not always decrease with group size, as it was sometimes favorable for individuals in larger groups to use riskier patches while remaining vigilant. Followers were also generally less vigilant than leaders. Indeed, followers needed to acquire more resources than leaders as only the latter could decide when to go to richer patches. Followers still benefit from dilution of predation risk compared to solitary individuals. For leaders, keeping their leadership status can be more important than incorporating new group members to increase dilution. We demonstrate that risk dilution impacts both optimal vigilance and space use, with fitness reward being tied to a member’s ability to influence group space use.</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, 12 Sep 2018 05:00:00 GMT “Sexual conflict and STIs: coevolution of sexually antagonistic host traits with a sexually transmitted infection” https://amnat.org/an/newpapers/JanWardlaw-A.html The DOI will be https://dx.doi.org/10.1086/700564 Abstract In many taxa, there is a conflict between the sexes over mating rate. The outcome of sexually antagonistic coevolution depends on the costs of mating and natural selection against sexually antagonistic traits. A sexually transmitted infection (STI) changes the relative strength of these costs. We study the three-way evolutionary interaction between male persistence, female resistance, and STI virulence for two types of STIs: a viability-reducing STI and a reproduction-reducing STI. A viability-reducing STI escalates conflict between the sexes. This leads to increased STI virulence (i.e., full coevolution) if the costs of sexually antagonistic traits occur through viability but not if the costs occur through reproduction. In contrast, a reproduction-reducing STI de-escalates the sexual conflict but STI virulence does not coevolve in response. We also investigated the establishment probability of STIs under different combinations of evolvability. Successful invasion by a viability-reducing STI becomes less likely if hosts (but not parasite) are evolvable, especially if only the female trait can evolve. A reproduction-reducing STI can almost always invade because it does not kill its host. We discuss how the evolution of host and parasite traits in a system with sexual conflict differs from a system with female mate choice. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700564 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700564">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;">I</span>n many taxa, there is a conflict between the sexes over mating rate. The outcome of sexually antagonistic coevolution depends on the costs of mating and natural selection against sexually antagonistic traits. A sexually transmitted infection (STI) changes the relative strength of these costs. We study the three-way evolutionary interaction between male persistence, female resistance, and STI virulence for two types of STIs: a viability-reducing STI and a reproduction-reducing STI. A viability-reducing STI escalates conflict between the sexes. This leads to increased STI virulence (i.e., full coevolution) if the costs of sexually antagonistic traits occur through viability but not if the costs occur through reproduction. In contrast, a reproduction-reducing STI de-escalates the sexual conflict but STI virulence does not coevolve in response. We also investigated the establishment probability of STIs under different combinations of evolvability. Successful invasion by a viability-reducing STI becomes less likely if hosts (but not parasite) are evolvable, especially if only the female trait can evolve. A reproduction-reducing STI can almost always invade because it does not kill its host. We discuss how the evolution of host and parasite traits in a system with sexual conflict differs from a system with female mate choice.</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, 12 Sep 2018 05:00:00 GMT “An empirical and mechanistic explanation of abundance-occupancy relationships for a critically endangered nomadic migrant” https://amnat.org/an/newpapers/JanWebb.html The DOI will be https://dx.doi.org/10.1086/700595 Abundance-occupancy relationships for a nomadic migrant are explained by variations in food abundance A&nbsp;positive abundance–occupancy relationship (AOR) is a pervasive pattern in macroecology implying species with larger geographic distributions are generally more locally abundant. But for species tracking variable resources in space and time, this is not always the case. This study by the Difficult Bird Research Group provides a rare empirical example of a negative AOR for the nomadic critically endangered swift parrot caused by dynamic pulses in the availability and location of food over seven years (2009–2015). In their breeding range (Tasmania, Australia), local densities of birds increased as food availability decreased, and vice versa. Although this study was conducted on a highly mobile species over a large geographic area, the results are likely relevant to partial migrants and less mobile species when their resources vary over smaller scales. This highlights the need to carefully consider the appropriate scales of sampling for AOR studies. Similarly, the association between the probability of occurrence and abundance is usually assumed to be positive and constant for species distribution models (SDMs). For the swift parrot, this relationship was positive but non-linear and varied with scale and between years due to differing degrees of spatial aggregation caused by changing food availability. Importantly, the results show that high abundance (or occupancy) does not necessarily equate to high quality habitat. Contrasting these two areas of research (i.e. SDMs and AORs) allows better identification of fluctuations in carrying capacity, priority sites, resource bottlenecks, and interpretation of dynamic SDMs. Further, understanding the causal mechanisms of AORs and how they change over time may provide an empirical means to understand changes in population size and range dynamics in variable environments. Abstract The positive abundance-occupancy relationship (AOR) is a pervasive pattern in macroecology. Similarly, the association between occupancy (or probability of occurrence) and abundance is also usually assumed to be positive and in most cases constant. Examples of AORs for nomadic species with variable distributions are extremely rare. Here we examined temporal and spatial trends in the AOR over seven years for a critically endangered nomadic migrant which relies on dynamic pulses in food availability to breed. We predicted a negative temporal relationship, where local mean abundances increase when the number of occupied sites decreases, and a positive relationship between local abundances and the probability of occurrence. We also predicted that these patterns are largely attributable to spatiotemporal variation in food abundance. The temporal AOR was significantly negative and annual food availability was significantly positively correlated with the number of occupied sites, but negatively correlated with abundance. Thus, as food availability decreased, local densities of birds increased, and vice-versa. The abundance – probability of occurrence relationship was positive and non-linear, but varied between years due to differing degrees of spatial aggregation caused by changing food availability. Importantly, high abundance (or occupancy) did not necessarily equate to high quality habitat and may be indicative of resource bottlenecks or exposure to other processes affecting vital rates. Our results provide a rare empirical example that highlights the complexity of AORs for species that target aggregated food resources in dynamic environments. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700595 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700595">Read the Article</a></i> </p> --> <p><b>Abundance-occupancy relationships for a nomadic migrant are explained by variations in food abundance </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;positive abundance–occupancy relationship (AOR) is a pervasive pattern in macroecology implying species with larger geographic distributions are generally more locally abundant. But for species tracking variable resources in space and time, this is not always the case. This study by the Difficult Bird Research Group provides a rare empirical example of a negative AOR for the nomadic critically endangered swift parrot caused by dynamic pulses in the availability and location of food over seven years (2009–2015). In their breeding range (Tasmania, Australia), local densities of birds increased as food availability decreased, and vice versa. </p><p>Although this study was conducted on a highly mobile species over a large geographic area, the results are likely relevant to partial migrants and less mobile species when their resources vary over smaller scales. This highlights the need to carefully consider the appropriate scales of sampling for AOR studies. Similarly, the association between the probability of occurrence and abundance is usually assumed to be positive and constant for species distribution models (SDMs). For the swift parrot, this relationship was positive but non-linear and varied with scale and between years due to differing degrees of spatial aggregation caused by changing food availability. Importantly, the results show that high abundance (or occupancy) does not necessarily equate to high quality habitat. </p><p>Contrasting these two areas of research (i.e. SDMs and AORs) allows better identification of fluctuations in carrying capacity, priority sites, resource bottlenecks, and interpretation of dynamic SDMs. Further, understanding the causal mechanisms of AORs and how they change over time may provide an empirical means to understand changes in population size and range dynamics in variable environments.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he positive abundance-occupancy relationship (AOR) is a pervasive pattern in macroecology. Similarly, the association between occupancy (or probability of occurrence) and abundance is also usually assumed to be positive and in most cases constant. Examples of AORs for nomadic species with variable distributions are extremely rare. Here we examined temporal and spatial trends in the AOR over seven years for a critically endangered nomadic migrant which relies on dynamic pulses in food availability to breed. We predicted a negative temporal relationship, where local mean abundances increase when the number of occupied sites decreases, and a positive relationship between local abundances and the probability of occurrence. We also predicted that these patterns are largely attributable to spatiotemporal variation in food abundance. The temporal AOR was significantly negative and annual food availability was significantly positively correlated with the number of occupied sites, but negatively correlated with abundance. Thus, as food availability decreased, local densities of birds increased, and vice-versa. The abundance – probability of occurrence relationship was positive and non-linear, but varied between years due to differing degrees of spatial aggregation caused by changing food availability. Importantly, high abundance (or occupancy) did not necessarily equate to high quality habitat and may be indicative of resource bottlenecks or exposure to other processes affecting vital rates. Our results provide a rare empirical example that highlights the complexity of AORs for species that target aggregated food resources in dynamic environments. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 12 Sep 2018 05:00:00 GMT “Fitness consequences of female alternative reproductive tactics in house mice (Mus musculus domesticus)” https://amnat.org/an/newpapers/JanFerrari.html The DOI will be https://dx.doi.org/10.1086/700567 Female house mice are known to raise their young either alone, or together with one or more other mothers in a communal nest. In the latter case, the mothers all care for the young indiscriminately. Whenever two alternative breeding tactics occurring in the same sex and population in nature are found, the question arises of how they can be evolutionarily stable. Manuela Ferrari and her colleagues at the University of Zurich (Anna Lindholm and Barbara König) studied communal and solitary breeding in a population of free-living house mice during a five year period (2007–2011). They find that females are more successful if they rear their litters solitarily, because pups in communal nests suffer from a lower survival probability. Why does communal breeding occur in the population, and at high rates (70%), if it reduces female fitness? The researchers show that older – likely also heavier and more experienced – females are less likely to rear their litters communally and instead have more solitary litters. Rearing young in a communal nest might therefore be a tactic that is followed only by females of lower overall condition. Such females might be either unable to rear litters on their own or to monopolize a nesting site and therefore take the least bad option, which is communal breeding instead of not breeding at all. These findings can help us to understand how behaviors that seem to have a cost, such as communal breeding in this example, can still be seen in nature if they are the best an individual can do in a given condition and situation. Abstract Alternative reproductive tactics are defined as discrete differences in morphological, physiological and/or behavioral traits associated with reproduction, which occur within the same sex and population. House mice provide a rare example for alternative reproductive tactics in females, which can either rear their young solitarily, or together with one or several other females in a communal nest. We assessed the fitness consequences of communal and solitary breeding in a wild population to understand how the two tactics can be evolutionarily stable. Females switched between the two tactics (with more than 50% of all females having two or more litters using both tactics), pointing towards communal and solitary breeding being two tactics within a single strategy and not two genetically determined strategies. Communal breeding resulted in reduced pup survival and negatively impacted female reproductive success. Older and likely heavier females more often reared their litters solitarily, indicating that females use a condition dependent strategy. Solitary breeding seems the more successful tactic and only younger and likely less competitive females might opt for communal nursing, even at the cost of increased pup mortality. This study emphasizes the importance of analyzing phenotypic plasticity and its role in cooperation in the context of female ARTs. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700567 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700567">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;">F</span>emale house mice are known to raise their young either alone, or together with one or more other mothers in a communal nest. In the latter case, the mothers all care for the young indiscriminately. Whenever two alternative breeding tactics occurring in the same sex and population in nature are found, the question arises of how they can be evolutionarily stable. Manuela Ferrari and her colleagues at the University of Zurich (Anna Lindholm and Barbara König) studied communal and solitary breeding in a population of free-living house mice during a five year period (2007–2011). They find that females are more successful if they rear their litters solitarily, because pups in communal nests suffer from a lower survival probability. Why does communal breeding occur in the population, and at high rates (70%), if it reduces female fitness? </p> <p>The researchers show that older – likely also heavier and more experienced – females are less likely to rear their litters communally and instead have more solitary litters. Rearing young in a communal nest might therefore be a tactic that is followed only by females of lower overall condition. Such females might be either unable to rear litters on their own or to monopolize a nesting site and therefore take the least bad option, which is communal breeding instead of not breeding at all. These findings can help us to understand how behaviors that seem to have a cost, such as communal breeding in this example, can still be seen in nature if they are the best an individual can do in a given condition and situation. </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>lternative reproductive tactics are defined as discrete differences in morphological, physiological and/or behavioral traits associated with reproduction, which occur within the same sex and population. House mice provide a rare example for alternative reproductive tactics in females, which can either rear their young solitarily, or together with one or several other females in a communal nest. We assessed the fitness consequences of communal and solitary breeding in a wild population to understand how the two tactics can be evolutionarily stable. Females switched between the two tactics (with more than 50% of all females having two or more litters using both tactics), pointing towards communal and solitary breeding being two tactics within a single strategy and not two genetically determined strategies. Communal breeding resulted in reduced pup survival and negatively impacted female reproductive success. Older and likely heavier females more often reared their litters solitarily, indicating that females use a condition dependent strategy. Solitary breeding seems the more successful tactic and only younger and likely less competitive females might opt for communal nursing, even at the cost of increased pup mortality. This study emphasizes the importance of analyzing phenotypic plasticity and its role in cooperation in the context of female ARTs. </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, 12 Sep 2018 05:00:00 GMT “From the past to the future: Considering the value and limits of evolutionary prediction” https://amnat.org/an/newpapers/JanShaw-A.html The DOI will be https://dx.doi.org/10.1086/700565 Abstract The complex interplay of the multiple genetic processes of evolution and the ecological contexts in which they proceed frustrates detailed identification of many of the states of populations, both past and future, that may be of interest. Prediction of rates of adaptation, in the sense of change in mean fitness, into the future would, however, valuably inform expectations for persistence of populations, especially in our era of rapid environmental change. Heavy investment in genomics and other molecular tools has fueled belief that those approaches can effectively predict adaptation into the future. I contest this view. Genome scans display the genomic footprints of the effects of natural selection and the other evolutionary processes over past generations, but it remains problematic to predict future change in mean fitness via genomic approaches. Here, I advocate for a direct approach to prediction of rates of ongoing adaptation. Following an overview of relevant quantitative genetic approaches, I outline the promise of the Fundamental Theorem of Natural Selection for study of the adaptive process. Empirical implementation of this concept can productively guide efforts both to deepen scientific insight about the process of adaptation and to inform measures for conserving the biota in the face of rapid environmental change. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700565 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700565">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 complex interplay of the multiple genetic processes of evolution and the ecological contexts in which they proceed frustrates detailed identification of many of the states of populations, both past and future, that may be of interest. Prediction of rates of adaptation, in the sense of change in mean fitness, into the future would, however, valuably inform expectations for persistence of populations, especially in our era of rapid environmental change. Heavy investment in genomics and other molecular tools has fueled belief that those approaches can effectively predict adaptation into the future. I contest this view. Genome scans display the genomic footprints of the effects of natural selection and the other evolutionary processes over past generations, but it remains problematic to predict future change in mean fitness via genomic approaches. Here, I advocate for a direct approach to prediction of rates of ongoing adaptation. Following an overview of relevant quantitative genetic approaches, I outline the promise of the Fundamental Theorem of Natural Selection for study of the adaptive process. Empirical implementation of this concept can productively guide efforts both to deepen scientific insight about the process of adaptation and to inform measures for conserving the biota in the face of rapid environmental change. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 12 Sep 2018 05:00:00 GMT “Delayed chemical defense: timely expulsion of herbivores reduces competition with neighboring plants” https://amnat.org/an/newpapers/JanBackmann.html The DOI will be https://dx.doi.org/10.1086/700577 Modeling shows that plants may use their herbivores to weaken competitors by delaying their defense reaction A&nbsp;plant faces several challenges in its life. It competes with neighboring plants for nutrients. At the same time, herbivores, such as caterpillars, want to eat it. Plants use chemical defenses to defend themselves against attackers. However, producing defense toxins is costly and slows the plant’s growth. Neighbors can easily outgrow a highly defended plant. Therefore, many plants use inducible defenses and produce defenses upon attack as a cost-saving strategy. However, there is a delay between the insect’s first bite and the plant’s defense response. In this time period, the plant is undefended and suffers feeding damage. Consequently, scientists had always assumed that natural selection should prefer small delay times. The authors of this study challenged this idea. This was motivated by the observation that caterpillars eat very little when they are small, whereas they consume 90% of all they eat in their entire lifetime in the last days before pupation. Therefore, it might be better to keep the small caterpillars. When they grow larger, and become more damaging, the defense should kick in. At that time, the plant should send the voracious caterpillar off – like a missile – to the neighbors. To explore this idea, the authors developed an individual-based model (Backmann, Grimm, Lin). They used experimental data from wild tobacco, Nicotiana attenuata, and its specialized herbivore, Manduca sexta from the lab (van Dam) and the field (Backmann, Baldwin). Using this model, the authors found that under strong competition and high herbivore pressure, the most efficient delay times were synchronized with the time the larvae need to grow large enough to severely damage neighboring plants. Based on this the authors concluded that being slow can be good, if the reaction is well-timed. Abstract Time delays in plant responses to insect herbivory are thought to be the principal disadvantage of induced over constitutive defenses, suggesting that there should be strong selection for rapid responses. However, observed time delays between the onset of herbivory and defense induction vary considerably among plants. We postulate that strong competition with conspecifics is an important co-determinant of the cost-benefit balance for induced responses. There may be a benefit to the plant to delay mounting a full defense response until the herbivore larvae are mobile enough to leave, and large enough to cause severe damage to neighboring plants. Thus, delayed responses could reduce the competitive pressure on the focal plant. To explore this idea, we developed an individual-based model using data from wild tobacco, Nicotiana attenuata, and its specialized herbivore, Manduca sexta. Chemical defense was assumed to be costly in terms of reduced plant growth. We used a genetic algorithm with the plant’s delay time as a heritable trait. A stationary distribution of delay times emerged, which under high herbivore densities peaked at higher values, which were related to the time larvae need to grow large enough to severely damage neighboring plants. Plants may thus tip the competitive balance by expelling insect herbivores to move to adjacent plants when the herbivores are most damaging. Thereby herbivores become part of a plant’s strategy for reducing competition and increasing fitness. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700577 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700577">Read the Article</a></i> </p> --> <p><b>Modeling shows that plants may use their herbivores to weaken competitors by delaying their defense reaction </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;plant faces several challenges in its life. It competes with neighboring plants for nutrients. At the same time, herbivores, such as caterpillars, want to eat it. Plants use chemical defenses to defend themselves against attackers. However, producing defense toxins is costly and slows the plant’s growth. Neighbors can easily outgrow a highly defended plant. Therefore, many plants use <i>inducible defenses and</i> produce defenses upon attack as a cost-saving strategy. However, there is a delay between the insect’s first bite and the plant’s defense response. In this time period, the plant is undefended and suffers feeding damage. Consequently, scientists had always assumed that natural selection should prefer small delay times. </p><p>The authors of this study challenged this idea. This was motivated by the observation that caterpillars eat very little when they are small, whereas they consume 90% of all they eat in their entire lifetime in the last days before pupation. Therefore, it might be better to keep the small caterpillars. When they grow larger, and become more damaging, the defense should kick in. At that time, the plant should send the voracious caterpillar off – like a missile – to the neighbors. </p><p>To explore this idea, the authors developed an individual-based model (Backmann, Grimm, Lin). They used experimental data from wild tobacco, <i>Nicotiana attenuata,</i> and its specialized herbivore, <i>Manduca sexta</i> from the lab (van Dam) and the field (Backmann, Baldwin). Using this model, the authors found that under strong competition and high herbivore pressure, the most efficient delay times were synchronized with the time the larvae need to grow large enough to severely damage neighboring plants. Based on this the authors concluded that being slow can be good, if the reaction is well-timed. </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;">T</span>ime delays in plant responses to insect herbivory are thought to be the principal disadvantage of induced over constitutive defenses, suggesting that there should be strong selection for rapid responses. However, observed time delays between the onset of herbivory and defense induction vary considerably among plants. We postulate that strong competition with conspecifics is an important co-determinant of the cost-benefit balance for induced responses. There may be a benefit to the plant to delay mounting a full defense response until the herbivore larvae are mobile enough to leave, and large enough to cause severe damage to neighboring plants. Thus, delayed responses could reduce the competitive pressure on the focal plant. To explore this idea, we developed an individual-based model using data from wild tobacco, <i>Nicotiana attenuata</i>, and its specialized herbivore, <i>Manduca sexta</i>. Chemical defense was assumed to be costly in terms of reduced plant growth. We used a genetic algorithm with the plant&rsquo;s delay time as a heritable trait. A stationary distribution of delay times emerged, which under high herbivore densities peaked at higher values, which were related to the time larvae need to grow large enough to severely damage neighboring plants. Plants may thus tip the competitive balance by expelling insect herbivores to move to adjacent plants when the herbivores are most damaging. Thereby herbivores become part of a plant&rsquo;s strategy for reducing competition and increasing fitness.</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, 12 Sep 2018 05:00:00 GMT “Metabolic theory and the temperature size rule explain the temperature dependence of population carrying capacity” https://amnat.org/an/newpapers/DecBernhardt.html The DOI will be https://dx.doi.org/10.1086/700114 Carrying capacity declines with warming, as predicted by the metabolic theory of ecology and the temperature-size rule Predicting population persistence and dynamics in the context of global change is a major challenge for ecology. Density of a population at carrying capacity is a key concept linking population dynamics to broader-scale patterns of biodiversity and population persistence. A widely held prediction is that population abundance at carrying capacity should decrease with warming. While it may seem counterintuitive that density should decrease when it’s warmer, the rationale is that as temperatures increase, individual metabolic rates are predicted to increase. If resource supply is limited and equal across all temperatures, then populations growing in warmer conditions should be able to support fewer individuals because each individual requires more metabolic resources to live. This prediction, which is based on the metabolic theory of ecology, has not been tested empirically. Here, using experimental populations of the green alga, Tetraselmis tetrahele, Joey Bernhardt, Jenn Sunday, and Mary O’Connor tested empirically whether effects of temperature on short-term metabolic performance (rates of photosynthesis and respiration) translate directly to effects of temperature on population dynamics. They measured per-capita metabolic rates and population abundances at carrying capacity across a temperature gradient spanning 5°C – 38°C. They found that carrying capacity declined with temperature, and that this decline in abundance was predicted by metabolic theory models. The temperature dependence of individual metabolic performance translated to population abundance. Concurrent with declines in abundance, they observed a linear decline in cell size of approximately 2% per degree Celsius, which is consistent with broadly observed patterns in unicellular organisms, known as the temperature-size rule. Their results indicate that outcomes of population dynamics across a range of temperatures reflect organismal responses to temperature via metabolic scaling, providing a general basis for forecasting population responses to global change.Abstract The temperature dependence of highly conserved subcellular metabolic systems affects ecological patterns and processes across scales, from organisms to ecosystems. Population density at carrying capacity plays an important role in evolutionary processes, biodiversity and ecosystem function, yet how it varies with temperature-dependent metabolism remains unclear. Though the exponential effect of temperature on intrinsic population growth rate, r, is well known, we still lack clear evidence that population density at carrying capacity, K, declines with increasing per-capita metabolic rate, as predicted by the metabolic theory of ecology (MTE). We experimentally tested whether temperature effects on photosynthesis propagate directly to population carrying capacity in a model species, the mobile phytoplankton Tetraselmis tetrahele. After maintaining populations at fixed resource supply and temperatures (6 levels) for 43 days, we found that carrying capacity declined with increasing temperature. This decline was predicted quantitatively when models included temperature-dependent metabolic rates and temperature-associated body size shifts. Our results demonstrate that warming reduces carrying capacity, and that temperature effects on body size and metabolic rate interact to determine how temperature affects population dynamics. These findings bolster efforts to relate metabolic temperature dependence to population and ecosystem patterns via MTE. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700114 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700114">Read the Article</a></i> </p> --> <p><b>Carrying capacity declines with warming, as predicted by the metabolic theory of ecology and the temperature-size rule </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>redicting population persistence and dynamics in the context of global change is a major challenge for ecology. Density of a population at carrying capacity is a key concept linking population dynamics to broader-scale patterns of biodiversity and population persistence. A widely held prediction is that population abundance at carrying capacity should decrease with warming. While it may seem counterintuitive that density should decrease when it’s warmer, the rationale is that as temperatures increase, individual metabolic rates are predicted to increase. If resource supply is limited and equal across all temperatures, then populations growing in warmer conditions should be able to support fewer individuals because each individual requires more metabolic resources to live. This prediction, which is based on the metabolic theory of ecology, has not been tested empirically. </p> <p>Here, using experimental populations of the green alga, <i>Tetraselmis tetrahele</i>, Joey Bernhardt, Jenn Sunday, and Mary O’Connor tested empirically whether effects of temperature on short-term metabolic performance (rates of photosynthesis and respiration) translate directly to effects of temperature on population dynamics. They measured per-capita metabolic rates and population abundances at carrying capacity across a temperature gradient spanning 5°C – 38°C. They found that carrying capacity declined with temperature, and that this decline in abundance was predicted by metabolic theory models. The temperature dependence of individual metabolic performance translated to population abundance. Concurrent with declines in abundance, they observed a linear decline in cell size of approximately 2% per degree Celsius, which is consistent with broadly observed patterns in unicellular organisms, known as the temperature-size rule. Their results indicate that outcomes of population dynamics across a range of temperatures reflect organismal responses to temperature via metabolic scaling, providing a general basis for forecasting population responses to global change.</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 temperature dependence of highly conserved subcellular metabolic systems affects ecological patterns and processes across scales, from organisms to ecosystems. Population density at carrying capacity plays an important role in evolutionary processes, biodiversity and ecosystem function, yet how it varies with temperature-dependent metabolism remains unclear. Though the exponential effect of temperature on intrinsic population growth rate, <i>r</i>, is well known, we still lack clear evidence that population density at carrying capacity, <i>K</i>, declines with increasing per-capita metabolic rate, as predicted by the metabolic theory of ecology (MTE). We experimentally tested whether temperature effects on photosynthesis propagate directly to population carrying capacity in a model species, the mobile phytoplankton <i>Tetraselmis tetrahele</i>. After maintaining populations at fixed resource supply and temperatures (6 levels) for 43 days, we found that carrying capacity declined with increasing temperature. This decline was predicted quantitatively when models included temperature-dependent metabolic rates and temperature-associated body size shifts. Our results demonstrate that warming reduces carrying capacity, and that temperature effects on body size and metabolic rate interact to determine how temperature affects population dynamics. These findings bolster efforts to relate metabolic temperature dependence to population and ecosystem patterns via MTE. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 07 Sep 2018 05:00:00 GMT “‘Her joyous enthusiasm for her life-work…’ Early women authors in The American Naturalist” https://amnat.org/an/newpapers/DecBronstein.html The DOI will be https://dx.doi.org/10.1086/700119 Who were the early women authors in The&nbsp;American Naturalist? The natural sciences in the 19th century were almost exclusively studied by men. Almost. But a small number of remarkable, pioneering women overcame deeply entrenched cultural barriers to publish their own contributions to the natural sciences. This journal began publication in 1867, and for decades was the leading venue in America for publishing in the natural sciences, broadly defined. Although most American Naturalist articles were male-authored, women did contribute articles even in the journal’s first decades. Over 60 women contributed a total of nearly 80 articles during the journal’s first half-century. Here, Bronstein and Bolnick examine these womens’ scientific contributions to The&nbsp;American Naturalist, as well as their lives and the challenges they faced to enter and stay active in science. How were they drawn into science despite the barriers to entry for women? How did some manage to establish life-long careers in science? Abstract Women have long been underrepresented in the natural sciences, and although great progress has been made in recent decades, many subtle and not-so-subtle barriers persist. In this context, it is easy to get the impression that the early history of ecology and evolutionary biology was exclusively the domain of male researchers. In fact, a number of women made very substantial contributions to The&nbsp;American Naturalist in its first decades. As part of a series of retrospective essays celebrating 150 years of this journal, we highlight the scientific contributions of the women who published in it during its first fifty years (1867–1916). We also discuss the diverse paths that their scientific careers took, and the barriers that they faced along the way. More forthcoming papers &raquo; <p><i>The DOI will be https://dx.doi.org/10.1086/700119 </i></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700119">Read the Article</a></i> </p> --><h2>Who were the early women authors in <i>The&nbsp;American Naturalist</i>?</h2> <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 natural sciences in the 19th century were almost exclusively studied by men. Almost. But a small number of remarkable, pioneering women overcame deeply entrenched cultural barriers to publish their own contributions to the natural sciences. This journal began publication in 1867, and for decades was the leading venue in America for publishing in the natural sciences, broadly defined. Although most <i>American Naturalist</i> articles were male-authored, women did contribute articles even in the journal’s first decades. Over 60 women contributed a total of nearly 80 articles during the journal’s first half-century. Here, Bronstein and Bolnick examine these womens’ scientific contributions to <i>The&nbsp;American Naturalist</i>, as well as their lives and the challenges they faced to enter and stay active in science. How were they drawn into science despite the barriers to entry for women? How did some manage to establish life-long careers in science? </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>omen have long been underrepresented in the natural sciences, and although great progress has been made in recent decades, many subtle and not-so-subtle barriers persist. In this context, it is easy to get the impression that the early history of ecology and evolutionary biology was exclusively the domain of male researchers. In fact, a number of women made very substantial contributions to <i>The&nbsp;American Naturalist</i> in its first decades. As part of a series of retrospective essays celebrating 150 years of this journal, we highlight the scientific contributions of the women who published in it during its first fifty years (1867&ndash;1916). We also discuss the diverse paths that their scientific careers took, and the barriers that they faced along the way. </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, 28 Aug 2018 05:00:00 GMT “Purring crickets: The evolution of a novel sexual signal” https://amnat.org/an/newpapers/DecTinghitella.html Read the Article Male crickets evolve novel ‘purring’ sound that attracts female mates. Are they crick-cats? Like us, many organisms communicate with one another using signals that can take the form of sounds, smells, colors, or behaviors. Communication between males and females of the same species is often required for reproduction, so when mating signals change dramatically there are important implications for speciation. Like any question about evolutionary change, when we study animal communication we usually do that by comparing species or other groups that have differed in signals for quite some time. But we cannot test definitively for a role of mating signals in creating and maintaining diversity unless we find a signal that has just evolved so that we can measure the signal and the receiver’s response to that signal at “time 0”, and then track the changes over time. Robin Tinghitella, Dale Broder, and colleagues recently discovered just such a situation when they visited the Kalaupapa National Historical Site on the Hawaiian island of Molokaʻi. Tinghitella has studied field crickets in Hawai‘i for 15 years and has been interested in the songs males produce by rubbing their wings together to attract females. Last May, just after dusk, she collected crickets on a lawn in Kalaupapa for the first time. She took them back to her room where she noticed a quiet purring sound. She instantly wondered whether she had a feline visitor. But the sound was coming from her box of crickets. In this unique place where there was no background anthropogenic noise, she was able to hear a totally novel cricket song for the first time! The Tinghitella lab group is calling the males who make this novel sound purring crickets—or crick-cats! Back in the lab, they began recording and characterizing the new song. It is much quieter, more broadband, and has a higher average peak frequency than a typical song from a male of this species. They also wondered if females could hear the new sound and use it to locate males. They played recordings to females from a speaker 1 meter away and found that about half of them could locate the speaker. This is such an exciting discovery—males are singing a brand new song and females can hear it and use it! In future work, the team will track this system over time to see whether and how the purring song coevolves with female receivers in real time—evolution in action! This one of very few discoveries of a novel sexual signal, and they will use it to better understand how new conversations begin and what they mean for boundaries between species. Abstract Opportunities to observe contemporary signal change are incredibly rare, but critical for understanding how diversity is created and maintained. We discovered a population of the Pacific field cricket (Teleogryllus oceanicus) with a newly evolved song (“purring”), different from any known cricket. Male crickets use song to attract females from afar and to court females once near. Teleogryllus oceanicus is well-known for sexual signal evolution, as exemplified by a recent signal loss. In this study, we characterized the new purring sound and investigated the role of the purr in long distance and short distance communication. The purring sound differed from typical ancestral calls in peak frequency, amplitude, and bandwidth. Further, the long-distance purring song facilitated mate location, though the role of courtship purring song is less clear. Our discovery of purring male crickets is an unprecedented opportunity to watch the emergence of a newly evolved sexual signal unfold in real time, and has potential to illuminate the mechanisms by which evolutionary novelties arise and coevolve between the sexes. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/700116"><strong><i>Read the Article</i></strong></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700116">Read the Article</a></i> </p> --> <p><b>Male crickets evolve novel &lsquo;purring&rsquo; sound that attracts female mates. Are they crick-cats? </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>ike us, many organisms communicate with one another using signals that can take the form of sounds, smells, colors, or behaviors. Communication between males and females of the same species is often required for reproduction, so when mating signals change dramatically there are important implications for speciation. Like any question about evolutionary change, when we study animal communication we usually do that by comparing species or other groups that have differed in signals for quite some time. But we cannot test definitively for a role of mating signals in creating and maintaining diversity unless we find a signal that has <i>just</i> evolved so that we can measure the signal and the receiver’s response to that signal at “time 0”, and then track the changes over time. </p><p>Robin Tinghitella, Dale Broder, and colleagues recently discovered just such a situation when they visited the Kalaupapa National Historical Site on the Hawaiian island of Molokaʻi. Tinghitella has studied field crickets in Hawai‘i for 15 years and has been interested in the songs males produce by rubbing their wings together to attract females. Last May, just after dusk, she collected crickets on a lawn in Kalaupapa for the first time. She took them back to her room where she noticed a quiet purring sound. She instantly wondered whether she had a feline visitor. But the sound was coming from her box of crickets. In this unique place where there was no background anthropogenic noise, she was able to hear a totally novel cricket song for the first time! The Tinghitella lab group is calling the males who make this novel sound purring crickets—or crick-cats! Back in the lab, they began recording and characterizing the new song. It is much quieter, more broadband, and has a higher average peak frequency than a typical song from a male of this species. They also wondered if females could hear the new sound and use it to locate males. They played recordings to females from a speaker 1 meter away and found that about half of them could locate the speaker. This is such an exciting discovery—males are singing a brand new song and females can hear it and use it! In future work, the team will track this system over time to see whether and how the purring song coevolves with female receivers in real time—evolution in action! This one of very few discoveries of a novel sexual signal, and they will use it to better understand how new conversations begin and what they mean for boundaries between species. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>pportunities to observe contemporary signal change are incredibly rare, but critical for understanding how diversity is created and maintained. We discovered a population of the Pacific field cricket (<i>Teleogryllus oceanicus</i>) with a newly evolved song (“purring”), different from any known cricket. Male crickets use song to attract females from afar and to court females once near. <i>Teleogryllus oceanicus</i> is well-known for sexual signal evolution, as exemplified by a recent signal loss. In this study, we characterized the new purring sound and investigated the role of the purr in long distance and short distance communication. The purring sound differed from typical ancestral calls in peak frequency, amplitude, and bandwidth. Further, the long-distance purring song facilitated mate location, though the role of courtship purring song is less clear. Our discovery of purring male crickets is an unprecedented opportunity to watch the emergence of a newly evolved sexual signal unfold in real time, and has potential to illuminate the mechanisms by which evolutionary novelties arise and coevolve between the sexes. </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, 28 Aug 2018 05:00:00 GMT “Transgenerational and within-generation plasticity in response to climate change: insights from a manipulative field experiment across an elevational gradient” https://amnat.org/an/newpapers/DecWadgymar.html Read the Article Transgenerational and within-generation plasticity interact and vary clinally in populations across elevation gradients Environmental conditions strongly influence an individual’s phenotype and fitness. Temporal and spatial variation in the landscape can favor the evolution of phenotypic plasticity, such that one individual can produce different phenotypes depending on the environment it encounters. However, we know very little about the extent to which the environment a parent experiences affects the phenotypes of the offspring, and whether phenotypic plasticity across generations interacts with plasticity that arises within generations. Given the importance of environmental variation in the evolution of plasticity, populations distributed across gradients may have evolved different strategies for responding to changes in the environment. Studies of transgenerational and within-generation plasticity can reveal potential mechanisms through which populations or species could mitigate the effects of rapid climate change. Here, Wadgymar, MacTavish, and Anderson examine transgenerational and within-generation plasticity in life history traits in response to climate change in sixteen populations of the perennial forb, Boechera stricta (Drummond’s rockcress, in the Brassicaceae) distributed across an elevational gradient in the Rocky Mountains of Colorado. In the field, the researchers manipulated snowpack and the timing of snowmelt in a two-generation reciprocal transplant experiment conducted in three common gardens established near the lower, intermediate, and higher range boundaries of Boechera’s distribution in this region. In the greenhouse, they exposed plants to conditions simulating high and low elevation sites. In the field, the scientists discovered that transgenerational plasticity in seed mass, seed dormancy, and seedling emergence varied clinally across an elevational gradient and differed between snow-removal and control treatments. The arid and warm conditions typical of low-elevation sites and the researchers’ snow-removal treatment caused plants to produce smaller and more dormant seeds in comparison to the less-arid, cooler conditions typical of high-elevation sites and the control treatment. Small seeds had a greater probability of being non-viable, and low-elevation genotypes produce smaller seeds than high-elevation genotypes. Altogether, these results suggest that climate change may have disproportionately negative consequences for low-elevation populations, and that these effects are mediated, in part, by transgenerational plasticity. The results demonstrate that the effects of climate change on transgenerational plasticity are complex and context-dependent. The researchers propose that future studies should incorporate the influence of parental effects in studies of climate change, adaptation, and species persistence. Abstract Parental environmental effects, or transgenerational plasticity, can influence an individual’s phenotype or fitness, yet remain underexplored in the context of global change. Using the perennial self-pollinating plant Boechera stricta, we explored the effects of climate change on transgenerational and within-generation plasticity in dormancy, germination, growth, and survival. We first conducted a snow removal experiment in the field, in which we transplanted 16 families of known origin into three common gardens at different elevations and exposed half of the siblings to contemporary snow dynamics and half to early snow removal. We planted the offspring of these individuals in a factorial manipulation of temperature and water level in the growth chamber, and reciprocally transplanted them across all parental environments in the field. The growth chamber experiment revealed that the effects of transgenerational plasticity persist in traits expressed after establishment, even when accounting for parental effects on seed mass. The field experiment showed that transgenerational and within-generation plasticity can interact and that plasticity varies clinally in populations distributed across elevations. These findings demonstrate that transgenerational plasticity can influence fitness-related traits and should be incorporated in studies of biological responses to climate change. Plasticidad transgeneracional e intrageneracional en respuesta a los cambios climáticos: Resultados de un experimento de campo manipulativo a través de un gradiente de elevación Los efectos ambientales parentales, o la plasticidad transgeneracional, pueden influir en el fenotipo y la adecuación (fitness) de un individuo, pero permanecen poco estudiados en el contexto de los cambios climáticos. Utilizando la planta perenne y de autofecundación, Boechera stricta, exploramos los efectos del cambio climático sobre la plasticidad transgeneracional e intrageneracional en la dormancia, la germinación, el crecimiento y la supervivencia. Primero realizamos un experimento de remoción de la nieve en el campo, en el que trasplantamos 16 familias de origen conocido en tres jardines comunes a diferentes elevaciones. Expusimos la mitad de los individuos a las dinámicas contemporáneas de nieve y la otra mitad a la eliminación temprana de la nieve. Plantamos a los descendientes de estos individuos siguiendo una manipulación factorial de temperatura y nivel de agua en el laboratorio, y los trasplantamos recíprocamente a través de todos los ambientes paternales en el campo. El experimento controlado en el laboratorio reveló que los efectos de la plasticidad transgeneracional persisten en rasgos expresados después del establecimiento, incluso cuando se contabilizan los efectos paternos en el peso de la semilla. El experimento de campo mostró que la plasticidad transgeneracional e intrageneracional pueden interactuar y que la plasticidad varía de forma clinal en las poblaciones distribuidas a través de las elevaciones. Estos hallazgos demuestran que la plasticidad transgeneracional puede influir en los rasgos relacionados con la adecuación y debe ser incorporada en estudios de respuestas biológicas al cambio climático. More forthcoming papers &raquo; <p><a href="https://dx.doi.org/10.1086/700097"><i>Read the Article</i></a></p> <!-- <p><i><a href="https://dx.doi.org/10.1086/700097">Read the Article</a></i> </p> --> <p><b>Transgenerational and within-generation plasticity interact and vary clinally in populations across elevation gradients </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>nvironmental conditions strongly influence an individual’s phenotype and fitness. Temporal and spatial variation in the landscape can favor the evolution of phenotypic plasticity, such that one individual can produce different phenotypes depending on the environment it encounters. However, we know very little about the extent to which the environment a parent experiences affects the phenotypes of the offspring, and whether phenotypic plasticity across generations interacts with plasticity that arises within generations. Given the importance of environmental variation in the evolution of plasticity, populations distributed across gradients may have evolved different strategies for responding to changes in the environment. Studies of transgenerational and within-generation plasticity can reveal potential mechanisms through which populations or species could mitigate the effects of rapid climate change. </p><p>Here, Wadgymar, MacTavish, and Anderson examine transgenerational and within-generation plasticity in life history traits in response to climate change in sixteen populations of the perennial forb, <i>Boechera stricta</i> (Drummond’s rockcress, in the Brassicaceae) distributed across an elevational gradient in the Rocky Mountains of Colorado. In the field, the researchers manipulated snowpack and the timing of snowmelt in a two-generation reciprocal transplant experiment conducted in three common gardens established near the lower, intermediate, and higher range boundaries of <i>Boechera</i>’s distribution in this region. In the greenhouse, they exposed plants to conditions simulating high and low elevation sites. </p><p>In the field, the scientists discovered that transgenerational plasticity in seed mass, seed dormancy, and seedling emergence varied clinally across an elevational gradient and differed between snow-removal and control treatments. The arid and warm conditions typical of low-elevation sites and the researchers’ snow-removal treatment caused plants to produce smaller and more dormant seeds in comparison to the less-arid, cooler conditions typical of high-elevation sites and the control treatment. Small seeds had a greater probability of being non-viable, and low-elevation genotypes produce smaller seeds than high-elevation genotypes. Altogether, these results suggest that climate change may have disproportionately negative consequences for low-elevation populations, and that these effects are mediated, in part, by transgenerational plasticity. The results demonstrate that the effects of climate change on transgenerational plasticity are complex and context-dependent. The researchers propose that future studies should incorporate the influence of parental effects in studies of climate change, adaptation, and species persistence. </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>arental environmental effects, or transgenerational plasticity, can influence an individual’s phenotype or fitness, yet remain underexplored in the context of global change. Using the perennial self-pollinating plant <i>Boechera stricta</i>, we explored the effects of climate change on transgenerational and within-generation plasticity in dormancy, germination, growth, and survival. We first conducted a snow removal experiment in the field, in which we transplanted 16 families of known origin into three common gardens at different elevations and exposed half of the siblings to contemporary snow dynamics and half to early snow removal. We planted the offspring of these individuals in a factorial manipulation of temperature and water level in the growth chamber, and reciprocally transplanted them across all parental environments in the field. The growth chamber experiment revealed that the effects of transgenerational plasticity persist in traits expressed after establishment, even when accounting for parental effects on seed mass. The field experiment showed that transgenerational and within-generation plasticity can interact and that plasticity varies clinally in populations distributed across elevations. These findings demonstrate that transgenerational plasticity can influence fitness-related traits and should be incorporated in studies of biological responses to climate change. </p> <h4>Plasticidad transgeneracional e intrageneracional en respuesta a los cambios climáticos: Resultados de un experimento de campo manipulativo a través de un gradiente de elevación</h4> <p>Los efectos ambientales parentales, o la plasticidad transgeneracional, pueden influir en el fenotipo y la adecuación (fitness) de un individuo, pero permanecen poco estudiados en el contexto de los cambios climáticos. Utilizando la planta perenne y de autofecundación, <i>Boechera stricta</i>, exploramos los efectos del cambio climático sobre la plasticidad transgeneracional e intrageneracional en la dormancia, la germinación, el crecimiento y la supervivencia. Primero realizamos un experimento de remoción de la nieve en el campo, en el que trasplantamos 16 familias de origen conocido en tres jardines comunes a diferentes elevaciones. Expusimos la mitad de los individuos a las dinámicas contemporáneas de nieve y la otra mitad a la eliminación temprana de la nieve. Plantamos a los descendientes de estos individuos siguiendo una manipulación factorial de temperatura y nivel de agua en el laboratorio, y los trasplantamos recíprocamente a través de todos los ambientes paternales en el campo. El experimento controlado en el laboratorio reveló que los efectos de la plasticidad transgeneracional persisten en rasgos expresados después del establecimiento, incluso cuando se contabilizan los efectos paternos en el peso de la semilla. El experimento de campo mostró que la plasticidad transgeneracional e intrageneracional pueden interactuar y que la plasticidad varía de forma clinal en las poblaciones distribuidas a través de las elevaciones. Estos hallazgos demuestran que la plasticidad transgeneracional puede influir en los rasgos relacionados con la adecuación y debe ser incorporada en estudios de respuestas biológicas al cambio climático.</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, 21 Aug 2018 05:00:00 GMT