ASN RSS http://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 17 Nov 2017 06:00:00 GMT 60 “Female density-dependent chemical warfare underlies fitness effects of group sex ratio in flour beetles” http://amnat.org/an/newpapers/MarKhan-A.html The DOI will be http://dx.doi.org/10.1086/695806 Females (not males) drive fitness effects of biased sex ratio via secreted toxins for resource (not sexual) competition Abstract In animals, skewed sex ratios can affect individual fitness either via sexual (e.g. intersexual conflict or intrasexual mate competition) or non-sexual interactions (e.g. sex-specific resource competition). Because most analyses of sex ratio focus on sexual interactions, the relative importance of sexual vs. non-sexual mechanisms remains unclear. We tested both mechanisms in the flour beetle Tribolium castaneum, where male-biased sex ratios increase female fitness relative to unbiased or female-biased groups. Although flour beetles show both sexual and non-sexual (resource) competition, we found that sexual interactions did not explain female fitness. Instead, female fecundity was dramatically reduced even after a brief exposure to flour conditioned by other females. Earlier studies suggested that secreted toxins might mediate density-dependent population growth in flour beetles. We identified ethyl- and methyl-benzoquinone (EBQ and MBQ; “quinones”), as components of adult stink glands that regulate female fecundity. In female-biased groups (i.e. at high female density), females upregulated quinones and suppressed each other’s reproduction. In male-biased groups, low female density and associated low quinone levels maximized fecundity. Thus, females appear to use quinones as weapons for female-specific, density-dependent interference competition. Our results underscore the importance of non-sexual interference competition that may often underlie the fitness consequences of skewed sex ratios. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695806 </i></p> <p><b>Females (not males) drive fitness effects of biased sex ratio via secreted toxins for resource (not sexual) competition </b></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;">I</span>n animals, skewed sex ratios can affect individual fitness either via sexual (e.g. intersexual conflict or intrasexual mate competition) or non-sexual interactions (e.g. sex-specific resource competition). Because most analyses of sex ratio focus on sexual interactions, the relative importance of sexual vs. non-sexual mechanisms remains unclear. We tested both mechanisms in the flour beetle <i>Tribolium castaneum</i>, where male-biased sex ratios increase female fitness relative to unbiased or female-biased groups. Although flour beetles show both sexual and non-sexual (resource) competition, we found that sexual interactions did not explain female fitness. Instead, female fecundity was dramatically reduced even after a brief exposure to flour conditioned by other females. Earlier studies suggested that secreted toxins might mediate density-dependent population growth in flour beetles. We identified ethyl- and methyl-benzoquinone (EBQ and MBQ; &ldquo;quinones&rdquo;), as components of adult stink glands that regulate female fecundity. In female-biased groups (i.e. at high female density), females upregulated quinones and suppressed each other&rsquo;s reproduction. In male-biased groups, low female density and associated low quinone levels maximized fecundity. Thus, females appear to use quinones as weapons for female-specific, density-dependent interference competition. Our results underscore the importance of non-sexual interference competition that may often underlie the fitness consequences of skewed sex ratios. <!-- <p><a href="http://dx.doi.org/10.1086/695806">Read&nbsp;the&nbsp;Article</a> </p> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Life history traits evolved jointly with climatic niche and disturbance regime in the genus Leucadendron (Proteaceae)” http://amnat.org/an/newpapers/FebTonnabel-A.html The DOI will be http://dx.doi.org/10.1086/695283 Abstract Organisms have evolved a diversity of life history strategies to cope with variation in their environment. Persistence as adults and/or seeds across recruitment events allows species to dampen the effects of environmental fluctuations. The evolution of life cycles with overlapping generations should thus permit the colonization of environments with uncertain recruitment. We tested this hypothesis in Leucadendron (Proteaceae), a genus with high functional diversity native to fire-prone habitats in the South African fynbos. We analyzed the joint evolution of life history traits (adult survival and seed bank strategies) and ecological niches (climate and fire regime) using comparative methods and accounting for various sources of uncertainty. In the fynbos, species with canopy seed banks that are unable to survive fire as adults display non-overlapping generations. In contrast, resprouters with an underground seed bank may be less threatened by extreme climatic events and fire intervals given their iteroparity and long-lasting seed bank. Life cycles with non-overlapping generations indeed jointly evolved with niches with less exposure to frost, but not with less exposure to drought. Canopy seed banks jointly evolved with niches with more predictable fire return, compared to underground seed banks. The evolution of extraordinary functional diversity among fynbos plants thus reflects, at least in part, the diversity of both climates and fire regimes in this region. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695283 </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;">O</span>rganisms have evolved a diversity of life history strategies to cope with variation in their environment. Persistence as adults and/or seeds across recruitment events allows species to dampen the effects of environmental fluctuations. The evolution of life cycles with overlapping generations should thus permit the colonization of environments with uncertain recruitment. We tested this hypothesis in <i>Leucadendron</i> (Proteaceae), a genus with high functional diversity native to fire-prone habitats in the South African fynbos. We analyzed the joint evolution of life history traits (adult survival and seed bank strategies) and ecological niches (climate and fire regime) using comparative methods and accounting for various sources of uncertainty. In the fynbos, species with canopy seed banks that are unable to survive fire as adults display non-overlapping generations. In contrast, resprouters with an underground seed bank may be less threatened by extreme climatic events and fire intervals given their iteroparity and long-lasting seed bank. Life cycles with non-overlapping generations indeed jointly evolved with niches with less exposure to frost, but not with less exposure to drought. Canopy seed banks jointly evolved with niches with more predictable fire return, compared to underground seed banks. The evolution of extraordinary functional diversity among fynbos plants thus reflects, at least in part, the diversity of both climates and fire regimes in this region. <!-- <a href="http://dx.doi.org/10.1086/695283">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Collective dispersal leads to variance in fitness and maintains offspring size variation within marine populations” http://amnat.org/an/newpapers/MarBurgess.html The DOI will be http://dx.doi.org/10.1086/695879 Collective dispersal selects for risk avoidance life histories, which consequently maintains variation in offspring size Larval dispersal in coastal environments is influenced by turbulent eddies that are several kilometers wide and last several weeks. These eddies can collect the larvae of benthic marine species (such as lobsters, sea urchins, reef fish) into dense groups that travel as coherent ‘packets’. Such collective dispersal means that sibling larvae released within a few days of each other would succeed (return to the coast and settle) or fail (are lost offshore) in groups. Therefore, turbulent dispersal generates unpredictable variation in fitness because some groups of offspring are lucky and others are not. How do marine life histories evolve in this turbulent and unpredictable setting to avoid occasional recruitment failures? Is it better to increase mean fitness, which also increases variability in fitness, or is it better to reduce variability even at the cost of a lower mean? By analogy with financial investment strategies, reducing variation at the expense of the mean is known as “bet hedging.” Scott Burgess, Robin Snyder, and Barry Rountree develop a mathematical model that predicts how turbulent dispersal influences the evolution of offspring size and spawning duration. They find that evolution favors offspring sizes that maximize fitness, even though this also increases the unpredictability of recruitment—there is no bet hedging. However, it can take a very long time for offspring sizes to evolve to the optimum, which means that types that differ in the size of offspring they produce can coexist for long periods. In nature, variation in offspring size within the same population is quite common. In the past, it’s been thought that this is the result of good and bad years or locations favoring different sizes. This paper shows that this kind of environmental variation is unnecessary to explain variation in size seen in nature: multiple offspring sizes can, in theory, coexist even in a uniform environment if larval dispersal is risky and the fates of larvae are correlated. Abstract Variance in fitness is well known to influence the outcome of evolution but is rarely considered in the theory of marine reproductive strategies. In coastal environments, turbulent mesoscale eddies can collect larvae into ‘packets’ resulting in collective dispersal. Larvae in packets return to the coast or are lost offshore in groups, producing variance in fitness. Using a Markov process to calculate fixation probabilities for competing phenotypes, we examine the evolution of offspring size and spawning duration in species with benthic adults and pelagic offspring. The offspring size that provides mothers with the highest mean fitness also generates the greatest variance in fitness, but pairwise invasion plots show that bet-hedging strategies are not evolutionarily stable: maximizing expected fitness correctly predicts the unique evolutionarily stable strategy. Nonetheless, fixation can take a long time. We find that selection to increase spawning duration as a risk-avoidance strategy to reduce the negative impacts of stochastic recruitment success can allow multiple offspring sizes to coexist in a population for extended periods. This has two important consequences for offspring size: 1) coexistence occurs over a broader range of sizes and is longer when spawning duration is longer, because longer spawning durations reduce variation in fitness and increase the time to fixation, and 2) longer spawning durations can compensate for having a non-optimal size and even allow less optimal sizes to reach fixation. Collective dispersal and longer spawning durations could effectively maintain offspring size variation even in the absence of good and bad years or locations. Empirical comparisons of offspring size would, therefore, not always reflect environment-specific differences in the optimal size. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695879 </i></p> <p><b>Collective dispersal selects for risk avoidance life histories, which consequently maintains variation in offspring size </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>arval dispersal in coastal environments is influenced by turbulent eddies that are several kilometers wide and last several weeks. These eddies can collect the larvae of benthic marine species (such as lobsters, sea urchins, reef fish) into dense groups that travel as coherent ‘packets’. Such collective dispersal means that sibling larvae released within a few days of each other would succeed (return to the coast and settle) or fail (are lost offshore) in groups. Therefore, turbulent dispersal generates unpredictable variation in fitness because some groups of offspring are lucky and others are not. How do marine life histories evolve in this turbulent and unpredictable setting to avoid occasional recruitment failures? Is it better to increase mean fitness, which also increases variability in fitness, or is it better to reduce variability even at the cost of a lower mean? By analogy with financial investment strategies, reducing variation at the expense of the mean is known as “bet hedging.” </p> <p>Scott Burgess, Robin Snyder, and Barry Rountree develop a mathematical model that predicts how turbulent dispersal influences the evolution of offspring size and spawning duration. They find that evolution favors offspring sizes that maximize fitness, even though this also increases the unpredictability of recruitment—there is no bet hedging. However, it can take a very long time for offspring sizes to evolve to the optimum, which means that types that differ in the size of offspring they produce can coexist for long periods. In nature, variation in offspring size within the same population is quite common. In the past, it’s been thought that this is the result of good and bad years or locations favoring different sizes. This paper shows that this kind of environmental variation is unnecessary to explain variation in size seen in nature: multiple offspring sizes can, in theory, coexist even in a uniform environment if larval dispersal is risky and the fates of larvae are correlated. </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;">V</span>ariance in fitness is well known to influence the outcome of evolution but is rarely considered in the theory of marine reproductive strategies. In coastal environments, turbulent mesoscale eddies can collect larvae into ‘packets’ resulting in collective dispersal. Larvae in packets return to the coast or are lost offshore in groups, producing variance in fitness. Using a Markov process to calculate fixation probabilities for competing phenotypes, we examine the evolution of offspring size and spawning duration in species with benthic adults and pelagic offspring. The offspring size that provides mothers with the highest mean fitness also generates the greatest variance in fitness, but pairwise invasion plots show that bet-hedging strategies are not evolutionarily stable: maximizing expected fitness correctly predicts the unique evolutionarily stable strategy. Nonetheless, fixation can take a long time. We find that selection to increase spawning duration as a risk-avoidance strategy to reduce the negative impacts of stochastic recruitment success can allow multiple offspring sizes to coexist in a population for extended periods. This has two important consequences for offspring size: 1) coexistence occurs over a broader range of sizes and is longer when spawning duration is longer, because longer spawning durations reduce variation in fitness and increase the time to fixation, and 2) longer spawning durations can compensate for having a non-optimal size and even allow less optimal sizes to reach fixation. Collective dispersal and longer spawning durations could effectively maintain offspring size variation even in the absence of good and bad years or locations. Empirical comparisons of offspring size would, therefore, not always reflect environment-specific differences in the optimal size. </p> <!-- <p> <a href="http://dx.doi.org/10.1086/695879">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Southern Ocean mesopelagic fish comply with Bergmann’s rule” http://amnat.org/an/newpapers/MarSaunders.html The DOI will be http://dx.doi.org/10.1086/695767 A&nbsp;new study from the British Antarctic Survey shows how lanternfish, small bioluminescent fish from the ocean’s twilight zone, are likely to respond to the warming of the Southern Ocean. These fish are one of the most abundant groups of organisms in the oceans and inhabit the twilight zone where they feed on small crustaceans. Their large collective biomass feeds a multitude of Southern Ocean predators, including penguins and seals. Changes in their distribution can have a devastating impact on these predators. The team studied patterns in body size of lanternfish in relation to temperature and latitude across the Scotia-Weddell sector of the Southern Ocean. By examining net samples and in situ temperature measurements from recent research surveys (2006-2009), it was found that lanternfish body size increases with decreasing temperature and increasing latitude. Furthermore, the team revealed that attaining a greater body size is vital for these organisms to survive in colder regions further south. If ocean warming trends continue, many smaller sub-Antarctic species will also be able to reach the far south, possibly displacing the larger Antarctic species presently there. Such small fish will be less energy rich than their larger counterparts, which will have ramifications for the penguins and seals that depend on them. Lead author Dr. Ryan Saunders says, “Understanding how lanternfish are governed by their environment is an important step to being able to predict how the Southern Ocean ecosystem will respond to future change.” The work was carried out as part of the Ecosystems program at the British Antarctic Survey, which examines the operation of Southern Ocean food-webs and their sensitivity to climatic variability and change. Lanternfish remain relatively understudied in the Southern Ocean, but are increasingly being recognized as an important alternative food source to Antarctic krill for many Southern Ocean predators. At present there is no developed fishery for lanternfish although they are receiving increasing international interest as a potential source of fishmeal. Abstract The applicability of macroecological rules to patterns in body size varies between taxa. One of the most examined is Bergmann’s rule, which states that body size increases with decreasing temperature and increasing latitude, although the rule is not universal and the proposed mechanisms underpinning it are multifarious and lack congruence. This study considers the degree to which Bergmann’s rule applies to the Southern Ocean mesopelagic fish community. We studied patterns in body size, temperature and latitude across a 12&deg; latitudinal gradient within the Scotia-Weddell sector. Intra-specific Bergmann’s rule was found to apply to 8 out of the 11 biomass-dominant species in the family Myctophidae. The rule was also apparent at an inter-specific level. Our study suggests that greater attainable body size in this community is a necessary attribute to reach colder regions further south. The adherence of these taxa to Bergmann’s rule enables such species to act as sentinels for identifying the drivers and consequences of ocean warming on the Southern Ocean ecosystem. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695767 </i></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>&nbsp;new study from the British Antarctic Survey shows how lanternfish, small bioluminescent fish from the ocean&rsquo;s twilight zone, are likely to respond to the warming of the Southern Ocean. These fish are one of the most abundant groups of organisms in the oceans and inhabit the twilight zone where they feed on small crustaceans. Their large collective biomass feeds a multitude of Southern Ocean predators, including penguins and seals. Changes in their distribution can have a devastating impact on these predators.</p> <p>The team studied patterns in body size of lanternfish in relation to temperature and latitude across the Scotia-Weddell sector of the Southern Ocean. By examining net samples and in situ temperature measurements from recent research surveys (2006-2009), it was found that lanternfish body size increases with decreasing temperature and increasing latitude. Furthermore, the team revealed that attaining a greater body size is vital for these organisms to survive in colder regions further south.</p> <p>If ocean warming trends continue, many smaller sub-Antarctic species will also be able to reach the far south, possibly displacing the larger Antarctic species presently there. Such small fish will be less energy rich than their larger counterparts, which will have ramifications for the penguins and seals that depend on them.</p> <p>Lead author Dr. Ryan Saunders says, &ldquo;Understanding how lanternfish are governed by their environment is an important step to being able to predict how the Southern Ocean ecosystem will respond to future change.&rdquo; The work was carried out as part of the Ecosystems program at the British Antarctic Survey, which examines the operation of Southern Ocean food-webs and their sensitivity to climatic variability and change. Lanternfish remain relatively understudied in the Southern Ocean, but are increasingly being recognized as an important alternative food source to Antarctic krill for many Southern Ocean predators. At present there is no developed fishery for lanternfish although they are receiving increasing international interest as a potential source of fishmeal.</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 applicability of macroecological rules to patterns in body size varies between taxa. One of the most examined is Bergmann&rsquo;s rule, which states that body size increases with decreasing temperature and increasing latitude, although the rule is not universal and the proposed mechanisms underpinning it are multifarious and lack congruence. This study considers the degree to which Bergmann&rsquo;s rule applies to the Southern Ocean mesopelagic fish community. We studied patterns in body size, temperature and latitude across a 12&deg; latitudinal gradient within the Scotia-Weddell sector. Intra-specific Bergmann&rsquo;s rule was found to apply to 8 out of the 11 biomass-dominant species in the family Myctophidae. The rule was also apparent at an inter-specific level. Our study suggests that greater attainable body size in this community is a necessary attribute to reach colder regions further south. The adherence of these taxa to Bergmann&rsquo;s rule enables such species to act as sentinels for identifying the drivers and consequences of ocean warming on the Southern Ocean ecosystem.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695767">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Mechanisms of assortative mating in speciation with gene flow: connecting theory and empirical research” http://amnat.org/an/newpapers/JanKopp-A.html The DOI will be http://dx.doi.org/10.1086/694889 Abstract The large body of theory on speciation with gene flow has brought to light fundamental differences in the effects of two types of mating rules on speciation: preference/trait rules, in which divergence in both (female) preferences and (male) mating traits is necessary for assortment, and matching rules, in which individuals mate with like individuals based on the presence of traits or alleles that they have in common. These rules can emerge from a variety of behavioral or other mechanisms in ways that are not always obvious. We discuss the theoretical properties of both types of rules and explain why speciation is generally thought to be more likely under matching rather than preference/trait rules. We furthermore discuss whether specific assortative mating mechanisms fall under a preference/trait or matching rule, present empirical evidence for these mechanisms, and propose empirical tests that could distinguish between them. The synthesis of the theoretical literature on these assortative mating rules with empirical studies of the mechanisms by which they act can provide important insights into the occurrence of speciation with gene flow. Finally, by providing a clear framework we hope to inspire greater alignment in the ways that both theoreticians and empiricists study mating rules and how these rules affect speciation through maintaining or eroding barriers to gene flow among closely related species or populations. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/694889 </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 large body of theory on speciation with gene flow has brought to light fundamental differences in the effects of two types of mating rules on speciation: preference/trait rules, in which divergence in both (female) preferences and (male) mating traits is necessary for assortment, and matching rules, in which individuals mate with like individuals based on the presence of traits or alleles that they have in common. These rules can emerge from a variety of behavioral or other mechanisms in ways that are not always obvious. We discuss the theoretical properties of both types of rules and explain why speciation is generally thought to be more likely under matching rather than preference/trait rules. We furthermore discuss whether specific assortative mating mechanisms fall under a preference/trait or matching rule, present empirical evidence for these mechanisms, and propose empirical tests that could distinguish between them. The synthesis of the theoretical literature on these assortative mating rules with empirical studies of the mechanisms by which they act can provide important insights into the occurrence of speciation with gene flow. Finally, by providing a clear framework we hope to inspire greater alignment in the ways that both theoreticians and empiricists study mating rules and how these rules affect speciation through maintaining or eroding barriers to gene flow among closely related species or populations. <!-- <a href="http://dx.doi.org/10.1086/694889">Read&nbsp;the&nbsp;Article</a> --> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Learning to cooperate: The evolution of social rewards in repeated interactions” http://amnat.org/an/newpapers/JanDridi.html The DOI will be http://dx.doi.org/10.1086/694822 Biologists Slimane Dridi and Erol Ak&ccedil;ay at the University of Pennsylvania demonstrate in a new mathematical model that evolution may shape the learning system of biological organisms to have preferences for increasing the chances of survival of others. The authors base their theoretical work on previous experimental discoveries made by other scientists, indicating that humans as well as other species find cooperation rewarding. An action is rewarding if the brain region specialized in processing rewards (the same region that is activated when we expect to eat sweet or salted foods) is activated when performing this action. Starting from this observation, the authors explored the possibility that natural selection could favor individuals who would be rewarded by the mere action of cooperating with a social partner. Combining the theories of reinforcement learning and natural selection, they investigate the situation where individuals in a population engage in social interactions that offer the possibility to cooperate or defect. These capture many of the interactions that occur in society and nature, such as the current problem of investing efforts to protect the climate, or the work performed by soldiers in ant colonies. The authors show that two main types of individuals are likely to take over an evolving population: individuals who the authors call “conditionally other-regarding”, meaning that they find mutual cooperation rewarding but are averse to exploitation (i.e., the situation where they cooperate but their partner defects), and selfish individuals who are only rewarded by defecting, which is the optimal action from a materialistic standpoint. Purely altruistic individuals who completely sacrifice their material gain to help others are generally not favored by natural selection. However, they can coexist with conditionally other-regarding individuals. This research helps us better understand the psychological motives behind the learning dynamics of helping behaviors in society and nature. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/694822 </i></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;">B</span>iologists Slimane Dridi and Erol Ak&ccedil;ay at the University of Pennsylvania demonstrate in a new mathematical model that evolution may shape the learning system of biological organisms to have preferences for increasing the chances of survival of others. The authors base their theoretical work on previous experimental discoveries made by other scientists, indicating that humans as well as other species find cooperation rewarding. An action is rewarding if the brain region specialized in processing rewards (the same region that is activated when we expect to eat sweet or salted foods) is activated when performing this action.</p> <p>Starting from this observation, the authors explored the possibility that natural selection could favor individuals who would be rewarded by the mere action of cooperating with a social partner. Combining the theories of reinforcement learning and natural selection, they investigate the situation where individuals in a population engage in social interactions that offer the possibility to cooperate or defect. These capture many of the interactions that occur in society and nature, such as the current problem of investing efforts to protect the climate, or the work performed by soldiers in ant colonies.</p> <p>The authors show that two main types of individuals are likely to take over an evolving population: individuals who the authors call &ldquo;conditionally other-regarding&rdquo;, meaning that they find mutual cooperation rewarding but are averse to exploitation (i.e., the situation where they cooperate but their partner defects), and selfish individuals who are only rewarded by defecting, which is the optimal action from a materialistic standpoint. Purely altruistic individuals who completely sacrifice their material gain to help others are generally not favored by natural selection. However, they can coexist with conditionally other-regarding individuals. This research helps us better understand the psychological motives behind the learning dynamics of helping behaviors in society and nature. <!-- <a href="http://dx.doi.org/10.1086/694822">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Coinfection timing drives host population dynamics through changes in virulence” http://amnat.org/an/newpapers/FebMarchetto-A.html The DOI will be http://dx.doi.org/10.1086/695316 Explicitly tracking coinfection timing can be important in a number of systems, such as when parasites share a vector Abstract Infections of one host by multiple parasites are common, and several studies have found that the order of parasite invasion can affect both within-host competition and disease severity. However, it is unclear to what extent coinfection timing might be important to consider when modeling parasite impacts on host populations. Using a model system of two viruses infecting barley, we found that simultaneous infections of the two viruses were significantly more damaging to hosts than sequential coinfections. While priority effects were evident in within-host concentrations of sequential coinfections, priority did not influence any parameters, such as virulence or transmission rate, that affect host population dynamics. We built a susceptible-infected model to examine whether the observed difference in coinfection virulence could impact host population dynamics under a range of scenarios. We found that coinfection timing can have an important, but context dependent, effect on projected host population dynamics. Studies that examine only simultaneous coinfections could inflate disease impact predictions. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695316 </i></p> <p><b>Explicitly tracking coinfection timing can be important in a number of systems, such as when parasites share a vector </b></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;">I</span>nfections of one host by multiple parasites are common, and several studies have found that the order of parasite invasion can affect both within-host competition and disease severity. However, it is unclear to what extent coinfection timing might be important to consider when modeling parasite impacts on host populations. Using a model system of two viruses infecting barley, we found that simultaneous infections of the two viruses were significantly more damaging to hosts than sequential coinfections. While priority effects were evident in within-host concentrations of sequential coinfections, priority did not influence any parameters, such as virulence or transmission rate, that affect host population dynamics. We built a susceptible-infected model to examine whether the observed difference in coinfection virulence could impact host population dynamics under a range of scenarios. We found that coinfection timing can have an important, but context dependent, effect on projected host population dynamics. Studies that examine only simultaneous coinfections could inflate disease impact predictions. <!-- <a href="http://dx.doi.org/10.1086/695316">Read&nbsp;the&nbsp;Article</a> --> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Sex-specific heterogeneity in fixed morphological traits influences individual fitness in a monogamous bird population” http://amnat.org/an/newpapers/JanPlard.html The DOI will be http://dx.doi.org/10.1086/694823 Population dynamics of a monogamous bird is driven by sex-specific life-history strategies Individuals differ in sex and intrinsic quality and their body condition changes over the course of the year—all of which results in individual differences in survival and reproductive abilities. Despite this fact, we lack empirical knowledge about how individual heterogeneity influences individual demographic performance and how it affects population dynamics, because models of population dynamics typically focus on average demographic rates, excluding possible differences in survival and reproductive performance among individuals. In this study, researchers from the Swiss Ornithological Institute, in collaboration with researchers from the Universities of Bern and of Bristol, study the influence of individual intrinsic quality and annual condition on the dynamics of a population of hoopoes. The hoopoe is a medium-sized monogamous bird species. The study population is located in the Swiss Alps, where hoopoes breed in nestboxes installed in vineyards and fruit-tree plantations. Results show that males and females contribute differently to population growth, with high-quality males contributing much more than females and low-quality males. High-quality males are characterized by large morphological size and high survival compared to low-quality males and females. Although females live shorter lives, they have a strong impact on annual reproductive success. Taking account of partner quality and availability, this study shows that annual reproductive success is influenced by the condition and the quality of both sexes. While individual condition influences the timing of breeding, which strongly affects clutch size, female quality and to a lesser extent male quality shape the number of fledglings produced by a pair. Thus, the study provides evidence that even in a monogamous bird species with biparental care, individuals’ contribution to the population can vary between males and females and is linked to individual traits. The study also suggests that population dynamics are more strongly driven by high-quality individuals, which has consequences for the management and conservation of wild populations. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/694823 </i></p> <p><b>Population dynamics of a monogamous bird is driven by sex-specific life-history strategies </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>ndividuals differ in sex and intrinsic quality and their body condition changes over the course of the year—all of which results in individual differences in survival and reproductive abilities. Despite this fact, we lack empirical knowledge about how individual heterogeneity influences individual demographic performance and how it affects population dynamics, because models of population dynamics typically focus on average demographic rates, excluding possible differences in survival and reproductive performance among individuals. In this study, researchers from the Swiss Ornithological Institute, in collaboration with researchers from the Universities of Bern and of Bristol, study the influence of individual intrinsic quality and annual condition on the dynamics of a population of hoopoes. </p><p>The hoopoe is a medium-sized monogamous bird species. The study population is located in the Swiss Alps, where hoopoes breed in nestboxes installed in vineyards and fruit-tree plantations. Results show that males and females contribute differently to population growth, with high-quality males contributing much more than females and low-quality males. High-quality males are characterized by large morphological size and high survival compared to low-quality males and females. Although females live shorter lives, they have a strong impact on annual reproductive success. Taking account of partner quality and availability, this study shows that annual reproductive success is influenced by the condition and the quality of both sexes. </p><p>While individual condition influences the timing of breeding, which strongly affects clutch size, female quality and to a lesser extent male quality shape the number of fledglings produced by a pair. Thus, the study provides evidence that even in a monogamous bird species with biparental care, individuals&rsquo; contribution to the population can vary between males and females and is linked to individual traits. The study also suggests that population dynamics are more strongly driven by high-quality individuals, which has consequences for the management and conservation of wild populations. <!-- <a href="http://dx.doi.org/10.1086/694823">Read&nbsp;the&nbsp;Article</a> --> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Extreme climate-induced life-history plasticity in an amphibian” http://amnat.org/an/newpapers/FebBecker.html The DOI will be http://dx.doi.org/10.1086/695315 Rainfall determines key life history decisions in a frog Blue whales live for more than 100 years, while adult mayflies may come and go in a day. Our own lifespan has increased by nearly 10 years over the past generation. We are used to a world where the life expectancy of animals is expected to vary by a few years, but what if your lifespan was linked to the weather? Researchers from University of Cape Town, South African National Biodiversity Institute, and Stellenbosch University have discovered a frog whose likelihood of survival appears to be linked to the amount of winter rainfall in South Africa’s biodiverse fynbos biome. Rose’s mountain toadlet comes out every winter to breed, but the amount of time the males spend waiting in puddles for females to arrive influences life-expectancy of these tiny toadlets. At only 20-30 mm long, these voiceless toadlets are easily overlooked, but the researchers, Francois Becker, John Measey, Krystal Tolley, and Res Altwegg, undertook a mark-recapture study over 7 years, to reach the finding that whether toadlets live long (4+ years), or just one year, depends on the weather. Surprisingly, ‘good weather’ for frogs (wet winters) was found to reduce survival as animals are thought to spend more time out in the open, while ‘bad weather’ (drier winters) means they abandon the breeding site quicker, resulting in these toadlets living to try again another winter. The correlation between survival and winter rainfall is truly remarkable, but the exact mechanism determining survival needs more work, and time is running out. The latest IUCN assessment is that this species is Critically Endangered and with climate in the area changing, it could be that changes in the winter rainfall regime could add to existing threats for this special species. While this is the first known example of a vertebrate with extreme changes survival that appear to be weather dependent, it may simply be due to a lack of sufficient research on the world’s smaller animal species. The researchers suggest that this kind of weather induced longevity change may be far more common than we are aware of, prompting more concern about how changes to the climate may affect wildlife. Abstract Age specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically less variable over time than other life history traits, such as fecundity or recruitment. Hence, adult survival is often conserved within a population over time, compared to the variation in survival found across taxa. In stark contrast to this general pattern, we report evidence of extreme short-term variation of adult survival in Rose’s Mountain Toadlet (Capensibufo rosei), which is apparently climate-induced. Over seven years, annual survival rate varied between 0.04 and 0.92, and 94% of this variation was explained by variation in breeding-season rainfall. Preliminary results suggest that this variation reflects adaptive life-history plasticity to a degree thus far unrecorded for any vertebrate, rather than direct rainfall induced mortality. In wet years, these toads appeared to achieve increased reproduction at the expense of their own survival whereas in dry years, their survival increased at the expense of reproduction. Such environmentally induced plasticity may reflect a diversity of life-history strategies not previously appreciated among vertebrates. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695315 </i></p> <p><b>Rainfall determines key life history decisions in a frog </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;">B</span>lue whales live for more than 100 years, while adult mayflies may come and go in a day. Our own lifespan has increased by nearly 10 years over the past generation. We are used to a world where the life expectancy of animals is expected to vary by a few years, but what if your lifespan was linked to the weather? Researchers from University of Cape Town, South African National Biodiversity Institute, and Stellenbosch University have discovered a frog whose likelihood of survival appears to be linked to the amount of winter rainfall in South Africa&rsquo;s biodiverse fynbos biome.</p> <p>Rose&rsquo;s mountain toadlet comes out every winter to breed, but the amount of time the males spend waiting in puddles for females to arrive influences life-expectancy of these tiny toadlets. At only 20-30 mm long, these voiceless toadlets are easily overlooked, but the researchers, Francois Becker, John Measey, Krystal Tolley, and Res Altwegg, undertook a mark-recapture study over 7 years, to reach the finding that whether toadlets live long (4+ years), or just one year, depends on the weather. Surprisingly, &lsquo;good weather&rsquo; for frogs (wet winters) was found to reduce survival as animals are thought to spend more time out in the open, while &lsquo;bad weather&rsquo; (drier winters) means they abandon the breeding site quicker, resulting in these toadlets living to try again another winter.</p> <p>The correlation between survival and winter rainfall is truly remarkable, but the exact mechanism determining survival needs more work, and time is running out. The latest IUCN assessment is that this species is Critically Endangered and with climate in the area changing, it could be that changes in the winter rainfall regime could add to existing threats for this special species.</p> <p>While this is the first known example of a vertebrate with extreme changes survival that appear to be weather dependent, it may simply be due to a lack of sufficient research on the world&rsquo;s smaller animal species. The researchers suggest that this kind of weather induced longevity change may be far more common than we are aware of, prompting more concern about how changes to the climate may affect wildlife.</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>ge specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically less variable over time than other life history traits, such as fecundity or recruitment. Hence, adult survival is often conserved within a population over time, compared to the variation in survival found across taxa. In stark contrast to this general pattern, we report evidence of extreme short-term variation of adult survival in Rose&rsquo;s Mountain Toadlet (<i>Capensibufo rosei</i>), which is apparently climate-induced. Over seven years, annual survival rate varied between 0.04 and 0.92, and 94% of this variation was explained by variation in breeding-season rainfall. Preliminary results suggest that this variation reflects adaptive life-history plasticity to a degree thus far unrecorded for any vertebrate, rather than direct rainfall induced mortality. In wet years, these toads appeared to achieve increased reproduction at the expense of their own survival whereas in dry years, their survival increased at the expense of reproduction. Such environmentally induced plasticity may reflect a diversity of life-history strategies not previously appreciated among vertebrates.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695315">Read&nbsp;the&nbsp;Article</a></p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Rising variability, not slowing down, as a leading indicator of a stochastically driven abrupt transition in a dryland ecosystem” http://amnat.org/an/newpapers/JanChen.html The DOI will be http://dx.doi.org/10.1086/694821 Leading indicators distinguish critical transition from stochastic transition, a long-term study in a dryland ecosystem Complex real ecosystems may abruptly shift from one alternative state to another near a critical point, which is characterized by a phenomenon called critical slowing down (CSD). In this study, the authors investigate whether the leading indicators of CSD will proceed to the impending transition. Empirical tests on leading indicators on ecological systems have largely been limited to studies employing microcosms and aquatic ecosystems, but not in field systems where stochasticity can play a significant role in driving transitions. This study presents the first empirical analysis of the temporal indicators of state transition in a dryland ecosystem. Combining empirical data and a simple modeling framework, prior to the transition the system showed no (or weak) signatures of CSD, but exhibited expected increasing trends in the variability, quantified by variance and skewness. These surprising results are consistent with the theoretical expectation of stochastically driven abrupt transitions that occur away from critical points; indeed, a driver of vegetation – annual rainfall – showed rising variance prior to the transition. The study suggests that rising variability can potentially serve as a leading indicator of stochastically driven transitions in real world ecosystems. Overall, the changing pattern of an ecosystem between alternative states sometimes may be not determinate, but just stochastic. The authors still find some evidence to forecast it. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/694821 </i></p> <p><b>Leading indicators distinguish critical transition from stochastic transition, a long-term study in a dryland ecosystem </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;">C</span>omplex real ecosystems may abruptly shift from one alternative state to another near a critical point, which is characterized by a phenomenon called critical slowing down (CSD). In this study, the authors investigate whether the leading indicators of CSD will proceed to the impending transition. Empirical tests on leading indicators on ecological systems have largely been limited to studies employing microcosms and aquatic ecosystems, but not in field systems where stochasticity can play a significant role in driving transitions. This study presents the first empirical analysis of the temporal indicators of state transition in a dryland ecosystem.</p> <p>Combining empirical data and a simple modeling framework, prior to the transition the system showed no (or weak) signatures of CSD, but exhibited expected increasing trends in the variability, quantified by variance and skewness. These surprising results are consistent with the theoretical expectation of stochastically driven abrupt transitions that occur away from critical points; indeed, a driver of vegetation &ndash; annual rainfall &ndash; showed rising variance prior to the transition. The study suggests that rising variability can potentially serve as a leading indicator of stochastically driven transitions in real world ecosystems.</p> <p>Overall, the changing pattern of an ecosystem between alternative states sometimes may be not determinate, but just stochastic. The authors still find some evidence to forecast it. <!-- <a href="http://dx.doi.org/10.1086/694821">Read&nbsp;the&nbsp;Article</a> --> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “The behavior and reproductive physiology of a solitary progressive provisioning vespid wasp: Evidence for a solitary-cycle origin of reproductive castes” http://amnat.org/an/newpapers/FebKelstrup-A.html The DOI will be http://dx.doi.org/10.1086/695336 Abstract The emergence of queens and workers from solitary antecedents mark a major evolutionary transition in the history of life. The solitary progressive provisioning wasp Synagris cornuta, a member of the subfamily basal to eusocial vespid wasps (Eumeninae), alternates between behavioral states characterized as queen-like and worker-like. Akin to a queen in eusocial wasps, a S.&nbsp;cornuta female initiates construction of a cell into which she oviposits, and then, similar to a worker, she cares for the brood as it develops. The Ovarian Groundplan (OGP) hypothesis for caste origins predicts that these behavioral states are associated with cyclical changes in ovarian status, where females performing queen-like tasks have eggs and those performing worker-like tasks possess only small oocytes. Our findings show strong support for the OGP hypothesis: the ovaries of S.&nbsp;cornuta females undergo differential oogenesis depending on the behavioral phase: the largest oocyte in the ovaries of females building a cell progress faster compared to that of females attending brood. Yet contrary to the OGP hypothesis, neither juvenile hormone nor ecdysteroids are associated with the reproductive cycle. Finally, the cuticular hydrocarbon profile showed no link with ovarian status, suggesting that fertility signals evolved subsequent to the emergence of group living. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695336 </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 emergence of queens and workers from solitary antecedents mark a major evolutionary transition in the history of life. The solitary progressive provisioning wasp <i>Synagris cornuta</i>, a member of the subfamily basal to eusocial vespid wasps (Eumeninae), alternates between behavioral states characterized as queen-like and worker-like. Akin to a queen in eusocial wasps, a <i>S.&nbsp;cornuta</i> female initiates construction of a cell into which she oviposits, and then, similar to a worker, she cares for the brood as it develops. The Ovarian Groundplan (OGP) hypothesis for caste origins predicts that these behavioral states are associated with cyclical changes in ovarian status, where females performing queen-like tasks have eggs and those performing worker-like tasks possess only small oocytes. Our findings show strong support for the OGP hypothesis: the ovaries of <i>S.&nbsp;cornuta</i> females undergo differential oogenesis depending on the behavioral phase: the largest oocyte in the ovaries of females building a cell progress faster compared to that of females attending brood. Yet contrary to the OGP hypothesis, neither juvenile hormone nor ecdysteroids are associated with the reproductive cycle. Finally, the cuticular hydrocarbon profile showed no link with ovarian status, suggesting that fertility signals evolved subsequent to the emergence of group living. <!-- <a href="http://dx.doi.org/10.1086/695336">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “A dynamic state model of migratory behavior and physiology to assess the consequences of environmental variation and anthropogenic disturbance on marine vertebrates” http://amnat.org/an/newpapers/FebPirotta.html The DOI will be http://dx.doi.org/10.1086/695135 Dynamic state modeling offers new insights into the migratory behavior and physiology of baleen whales Animals that migrate between their feeding and breeding grounds are subject to intense physiological pressure. On the feeding grounds, they must acquire a large portion of the energy they need to cover their travel and reproductive costs, before returning to the breeding grounds where they may exhaust the accumulated resources. This paper explores the mechanisms underlying this complex trade-off and suggests hypotheses on the processes driving migratory behavior, with blue whales as an example. Researchers at Washington State University, in collaboration with colleagues from the University of California Santa Cruz, Oregon State University, and Stanford University, have combined their expertise and available data on the ecology, feeding behavior, movements, energetics, and reproduction of migrating blue whales to develop a model describing a female’s optimal behavior over time. They find that migration emerges from the animals tracking the seasonal variability of prey in their range, while having to return to the breeding grounds. The results also show that female blue whales must feed on the breeding grounds to sustain the large costs of lactation, while pregnancy is energetically less costly. The authors then use the model to demonstrate how environmental changes could disproportionately affect reproductive success depending on how whales react and adjust to a perturbed environment. They also predict that the impact of localized, acute disturbance from human activities depends on how whales change their behavior, while chronic, but weaker, disturbances are expected to have limited short-term effects on reproduction. Blue whale migration appears to balance access to sufficient food resources with the constraints of reproduction. The proposed approach could be applied to other migratory species to disentangle similar trade-offs. Abstract Integrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs and the environment. We applied the framework to blue whales (Balaenoptera musculus) in the Eastern North Pacific Ocean, and explored the effects of environmental and anthropogenic perturbations on female reproductive success. We demonstrate the emergence of migration to track prey resources, enabling us to quantify the trade-offs among capital breeding, body condition, and metabolic expenses. We predict that periodic climatic oscillations affect reproductive success less than unprecedented environmental changes do. The effect of localized, acute anthropogenic impacts depended on whales’ behavioral response to the disturbance; chronic, but weaker, disturbances had little effect on reproductive success. Because we link behavior and vital rates by modeling individuals’ energetic budgets, we provide a general framework to investigate the ecology of migration and assess the population consequences of disturbance, while identifying critical knowledge gaps. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695135 </i></p> <p><b>Dynamic state modeling offers new insights into the migratory behavior and physiology of baleen whales </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>nimals that migrate between their feeding and breeding grounds are subject to intense physiological pressure. On the feeding grounds, they must acquire a large portion of the energy they need to cover their travel and reproductive costs, before returning to the breeding grounds where they may exhaust the accumulated resources. This paper explores the mechanisms underlying this complex trade-off and suggests hypotheses on the processes driving migratory behavior, with blue whales as an example.</p> <p>Researchers at Washington State University, in collaboration with colleagues from the University of California Santa Cruz, Oregon State University, and Stanford University, have combined their expertise and available data on the ecology, feeding behavior, movements, energetics, and reproduction of migrating blue whales to develop a model describing a female&rsquo;s optimal behavior over time. They find that migration emerges from the animals tracking the seasonal variability of prey in their range, while having to return to the breeding grounds. The results also show that female blue whales must feed on the breeding grounds to sustain the large costs of lactation, while pregnancy is energetically less costly.</p> <p>The authors then use the model to demonstrate how environmental changes could disproportionately affect reproductive success depending on how whales react and adjust to a perturbed environment. They also predict that the impact of localized, acute disturbance from human activities depends on how whales change their behavior, while chronic, but weaker, disturbances are expected to have limited short-term effects on reproduction. Blue whale migration appears to balance access to sufficient food resources with the constraints of reproduction. The proposed approach could be applied to other migratory species to disentangle similar trade-offs.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">I</span>ntegrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs and the environment. We applied the framework to blue whales (<i>Balaenoptera musculus</i>) in the Eastern North Pacific Ocean, and explored the effects of environmental and anthropogenic perturbations on female reproductive success. We demonstrate the emergence of migration to track prey resources, enabling us to quantify the trade-offs among capital breeding, body condition, and metabolic expenses. We predict that periodic climatic oscillations affect reproductive success less than unprecedented environmental changes do. The effect of localized, acute anthropogenic impacts depended on whales&rsquo; behavioral response to the disturbance; chronic, but weaker, disturbances had little effect on reproductive success. Because we link behavior and vital rates by modeling individuals&rsquo; energetic budgets, we provide a general framework to investigate the ecology of migration and assess the population consequences of disturbance, while identifying critical knowledge gaps.</p> <!--<p> <a href="http://dx.doi.org/10.1086/695135">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Temperature-dependent species interactions shape priority effects and the persistence of unequal competitors” http://amnat.org/an/newpapers/FebGrainger.html The DOI will be http://dx.doi.org/10.1086/695688 Temperature-dependent trophic interactions strengthen priority effects and shift competitive outcomes ‘Priority effects’ occur when an early arriving species alters the long-term make-up of an ecological community. Although common in nature, scientists are only beginning to understand the conditions under which priority effects arise. Tess Grainger and colleagues at the University of Toronto hypothesized that priority effects should be stronger at high temperatures, as warming speeds up growth rates and feeding, allowing early arrivers to more rapidly impact a shared environment. They tackled this prediction using an experiment with two competing aphid species and a shared milkweed host, and demonstrated that warming strengthens priority effects by simultaneously causing a more rapid induction of milkweed defenses and a faster depletion of the plant resource. These changes were matched with a shift in dispersal rates at higher temperature that are likely to influence the timing of species’ arrival at a local plant. This experiment tests emerging theory on the temperature-dependence of trophic interactions, and presents and tests new hypotheses that link temperature, priority effects and dispersal across spatial and temporal scales. Abstract The order of species arrival at a site can determine the outcome of competitive interactions when early arrivers alter the environment or deplete shared resources. These priority effects are predicted to be stronger at high temperatures, as higher vital rates caused by warming allows early arrivers to more rapidly impact a shared environment. We tested this prediction using a pair of congeneric aphid species that specialize on milkweed plants. We manipulated temperature and arrival order of the two aphid species, and measured aphid population dynamics and milkweed survival and defensive traits. We found that warming increased the impact of aphids on the quantity and quality of milkweed, which amplified the importance of priority effects by increasing the competitive exclusion of the inferior competitor when it arrived late. Warming also enhanced interspecific differences in dispersal, which could alter relative arrival times at a regional scale. Our experiment provides a first link between temperature-dependent trophic interactions, priority effects and dispersal. This study suggests that the indirect and cascading effects of temperature observed here may be important determinants of diversity in the temporally and spatially complex landscapes that characterize ecological communities. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695688 </i></p> <p><b>Temperature-dependent trophic interactions strengthen priority effects and shift competitive outcomes </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;">&lsquo;P</span>riority effects&rsquo; occur when an early arriving species alters the long-term make-up of an ecological community. Although common in nature, scientists are only beginning to understand the conditions under which priority effects arise. Tess Grainger and colleagues at the University of Toronto hypothesized that priority effects should be stronger at high temperatures, as warming speeds up growth rates and feeding, allowing early arrivers to more rapidly impact a shared environment. They tackled this prediction using an experiment with two competing aphid species and a shared milkweed host, and demonstrated that warming strengthens priority effects by simultaneously causing a more rapid induction of milkweed defenses and a faster depletion of the plant resource. These changes were matched with a shift in dispersal rates at higher temperature that are likely to influence the timing of species&rsquo; arrival at a local plant. This experiment tests emerging theory on the temperature-dependence of trophic interactions, and presents and tests new hypotheses that link temperature, priority effects and dispersal across spatial and temporal scales. </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 order of species arrival at a site can determine the outcome of competitive interactions when early arrivers alter the environment or deplete shared resources. These priority effects are predicted to be stronger at high temperatures, as higher vital rates caused by warming allows early arrivers to more rapidly impact a shared environment. We tested this prediction using a pair of congeneric aphid species that specialize on milkweed plants. We manipulated temperature and arrival order of the two aphid species, and measured aphid population dynamics and milkweed survival and defensive traits. We found that warming increased the impact of aphids on the quantity and quality of milkweed, which amplified the importance of priority effects by increasing the competitive exclusion of the inferior competitor when it arrived late. Warming also enhanced interspecific differences in dispersal, which could alter relative arrival times at a regional scale. Our experiment provides a first link between temperature-dependent trophic interactions, priority effects and dispersal. This study suggests that the indirect and cascading effects of temperature observed here may be important determinants of diversity in the temporally and spatially complex landscapes that characterize ecological communities. </p> <p><!-- <a href="http://dx.doi.org/10.1086/695688">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Temperature dependent growth and fission rate plasticity drive seasonal and geographic changes in body size in a clonal sea anemone” http://amnat.org/an/newpapers/FebRyan.html The DOI will be http://dx.doi.org/10.1086/695496 Fission rate plasticity allows clonal animals to track rapid changes in optimal body size through time and space Phenotypic plasticity, or the ability of individuals to continuously refine their morphology in response to changing conditions, presents a major challenge when predicting the ecological and evolutionary effects of environmental change. The “temperature-size rule” is a commonly observed pattern in animals where individuals grow to be smaller as adults when conditions are warmer. In aquatic animals, this pattern may reflect an increasing risk of oxygen limitation as water warms, favoring smaller bodied animals with a higher surface area to volume ratio. Clonal animals may be able to change size throughout their lives by adjusting the rate at which they grow versus divide. This flexibility may allow them to track a changing optimal body size as the environment changes, but can also influence patterns of investment in asexual and sexual reproduction. Using lab experiments and field observations, Will H. Ryan demonstrated that changes in the fission rate and average body size of the clonal sea anemone, Diadumene lineata, follow seasonal temperature changes. He grew anemones collected from across the species’ US Atlantic range (Florida, Georgia, and Massachusetts) in chambers mimicking seasonal temperature patterns found at these sites. The year-long experiment showed that annual patterns of growth, size, and clonal investment are highly dependent on local temperature patterns, leading to a gradient in the degree of asexuality expressed across the species range. Northern populations stay large and divide infrequently, whereas southern sites stay small and divide all year. Intermediate sites alternate between phases of individual growth and clonal proliferation. Variation in the response among individuals from different sites suggests that natural selection may be able to shape these patterns. For organisms with complex life cycles, like these sea anemones, environmental variation not only alters the speed of growth and development, but can also change the timing and nature of major life history events, such as fission. Abstract The temperature-size rule (TSR) is a commonly observed pattern where adult body size is negatively correlated with developmental temperature. In part, this may occur as a consequence of allometric scaling, where changes in the ratio of surface area to mass limit oxygen diffusion as body size increases. As oxygen demand increases with temperature, a smaller body should be favored as temperature increases. For clonal animals, small changes in growth and/or fission rate can rapidly alter the average body size of clonal descendants. Here I test the hypothesis that the clonal sea anemone Diadumene lineata is able to track an optimal body size through seasonal temperature changes using fission rate plasticity. Individuals from three regions (Florida, Georgia and Massachusetts) across the species’ latitudinal range were grown in a year-long reciprocal common garden experiment mimicking seasonal temperature changes at three sites. Average body size was found to be smaller and fission rates higher in warmer conditions, consistent with the TSR pattern. However, seasonal size and fission patterns reflect a complex interaction between region-specific thermal reaction norms and the local temperature regime. These details provide insight into both the range of conditions required for oxygen limitation to contribute to a negative correlation between body size and temperature and the role that fission rate plasticity can play in tracking a rapidly changing optimal phenotype. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695496 </i></p> <p><b>Fission rate plasticity allows clonal animals to track rapid changes in optimal body size through time and space </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>henotypic plasticity, or the ability of individuals to continuously refine their morphology in response to changing conditions, presents a major challenge when predicting the ecological and evolutionary effects of environmental change. The &ldquo;temperature-size rule&rdquo; is a commonly observed pattern in animals where individuals grow to be smaller as adults when conditions are warmer. In aquatic animals, this pattern may reflect an increasing risk of oxygen limitation as water warms, favoring smaller bodied animals with a higher surface area to volume ratio. Clonal animals may be able to change size throughout their lives by adjusting the rate at which they grow versus divide. This flexibility may allow them to track a changing optimal body size as the environment changes, but can also influence patterns of investment in asexual and sexual reproduction.</p> <p>Using lab experiments and field observations, Will H. Ryan demonstrated that changes in the fission rate and average body size of the clonal sea anemone, <i>Diadumene lineata</i>, follow seasonal temperature changes. He grew anemones collected from across the species&rsquo; US Atlantic range (Florida, Georgia, and Massachusetts) in chambers mimicking seasonal temperature patterns found at these sites. The year-long experiment showed that annual patterns of growth, size, and clonal investment are highly dependent on local temperature patterns, leading to a gradient in the degree of asexuality expressed across the species range. Northern populations stay large and divide infrequently, whereas southern sites stay small and divide all year. Intermediate sites alternate between phases of individual growth and clonal proliferation. Variation in the response among individuals from different sites suggests that natural selection may be able to shape these patterns.</p> <p>For organisms with complex life cycles, like these sea anemones, environmental variation not only alters the speed of growth and development, but can also change the timing and nature of major life history events, such as fission. </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 temperature-size rule (TSR) is a commonly observed pattern where adult body size is negatively correlated with developmental temperature. In part, this may occur as a consequence of allometric scaling, where changes in the ratio of surface area to mass limit oxygen diffusion as body size increases. As oxygen demand increases with temperature, a smaller body should be favored as temperature increases. For clonal animals, small changes in growth and/or fission rate can rapidly alter the average body size of clonal descendants. Here I test the hypothesis that the clonal sea anemone <i>Diadumene lineata </i>is able to track an optimal body size through seasonal temperature changes using fission rate plasticity. Individuals from three regions (Florida, Georgia and Massachusetts) across the species’ latitudinal range were grown in a year-long reciprocal common garden experiment mimicking seasonal temperature changes at three sites. Average body size was found to be smaller and fission rates higher in warmer conditions, consistent with the TSR pattern. However, seasonal size and fission patterns reflect a complex interaction between region-specific thermal reaction norms and the local temperature regime. These details provide insight into both the range of conditions required for oxygen limitation to contribute to a negative correlation between body size and temperature and the role that fission rate plasticity can play in tracking a rapidly changing optimal phenotype. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695496">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Leaf form evolution in Viburnum parallels variation within individual plants” http://amnat.org/an/newpapers/FebSpriggs-A.html The DOI will be http://dx.doi.org/10.1086/695337 Abstract Few studies have critically evaluated how morphological variation within individual organisms corresponds to variation within and among species. Sub-individual variation in plants facilitates such studies because their indeterminate, modular growth generates multiple serially homologous structures along growing axes. Focusing on leaf form, we evaluate how sub-individual trait variation relates to leaf evolution across Viburnum, a clade of woody angiosperms. In Viburnum we infer multiple independent origins of wide/lobed leaves with toothed margins from ancestors with elliptical, smooth-margined leaves. We document leaf variation along the branches of individual plants of 28 species and among populations across the wide range of V.&nbsp;dentatum. We conclude that when novel leaf forms evolved in Viburnum, they were intercalated at the beginning of the seasonal leaf sequence, which then generated a repeated spectrum of leaf forms along each branch (seasonal heteroblasty). We hypothesize that the existence of such a spectrum then facilitated additional evolutionary shifts, including reversions to more ancestral forms. We argue that the recurrent production of alternative phenotypes provides opportunities to canalize the production of particular forms, and that this phenomenon has played an important role in generating macro-scale patterns. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695337 </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;">F</span>ew studies have critically evaluated how morphological variation within individual organisms corresponds to variation within and among species. Sub-individual variation in plants facilitates such studies because their indeterminate, modular growth generates multiple serially homologous structures along growing axes. Focusing on leaf form, we evaluate how sub-individual trait variation relates to leaf evolution across <i>Viburnum</i>, a clade of woody angiosperms. In <i>Viburnum</i> we infer multiple independent origins of wide/lobed leaves with toothed margins from ancestors with elliptical, smooth-margined leaves. We document leaf variation along the branches of individual plants of 28 species and among populations across the wide range of <i>V.&nbsp;dentatum</i>. We conclude that when novel leaf forms evolved in <i>Viburnum</i>, they were intercalated at the beginning of the seasonal leaf sequence, which then generated a repeated spectrum of leaf forms along each branch (seasonal heteroblasty). We hypothesize that the existence of such a spectrum then facilitated additional evolutionary shifts, including reversions to more ancestral forms. We argue that the recurrent production of alternative phenotypes provides opportunities to canalize the production of particular forms, and that this phenomenon has played an important role in generating macro-scale patterns. <!-- <a href="http://dx.doi.org/10.1086/695337">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Using human vision to detect variation in avian coloration: How bad is it?” http://amnat.org/an/newpapers/FebBergeron.html The DOI will be http://dx.doi.org/10.1086/695282 Human vision detects most of the variation in animal color in the visible range Biologists have long known that animals differ in their visual systems. Species often differ in the number and types of cone cells in their eyes. These differences in visual systems have led to the conclusion that human vision can never be used to assess variation in animal coloration. This idea stands in contrast with the fact that many productive research programs on color pattern evolution have relied on human vision. Are humans missing the majority of color variation in nature and, instead, only investigating a narrow subset of variation? Admittedly, humans cannot detect ultraviolet, far-red or polarized signals. However, the question remains as to whether humans are failing to detect the bulk of color variation in the visible range. Bergeron and Fuller addressed this question by using a methodology that should be flawed by human subjectivity and comparing it to a methodology that is free of human perceptual biases. They compared the coloration of bird specimens from a museum with the coloration of bird images from a field guide (see image at right). They found that field guide images detected the vast majority of the variation in coloration that was present in the museum specimens. This means that human vision detects the major patterns in coloration in the visible range. Human vision cannot be used to say which color patterns are more or less conspicuous to another species, but it can be used to detect major patterns in animal coloration in the visible spectrum in nature. Abstract Assessing variation in animal coloration is difficult as animals differ in their visual system properties. This has led some to propose that human vision can never be used to evaluate coloration, yet many studies have a long history of relying on human vision. To reconcile these views, we compared the reflectance spectra of preserved avian plumage elements with two measures that are humans biased: RGB values from digital photographs and the corresponding reflectance spectra from a field guide. We measured 73 plumage elements across 14 bird species. The field guide reflectance spectra were drastically different from that of the actual birds, particularly for blue elements. However, principal components analyses on all three data sets indicated remarkably similar data structure. We conclude that human vision can detect much of the variation in coloration in the visible range, providing fodder for subsequent studies in ecology, evolution, behavior, and visual ecology. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695282 </i></p> <p><b>Human vision detects most of the variation in animal color in the visible range </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;">B</span>iologists have long known that animals differ in their visual systems. Species often differ in the number and types of cone cells in their eyes. These differences in visual systems have led to the conclusion that human vision can never be used to assess variation in animal coloration. This idea stands in contrast with the fact that many productive research programs on color pattern evolution have relied on human vision. Are humans missing the majority of color variation in nature and, instead, only investigating a narrow subset of variation? Admittedly, humans cannot detect ultraviolet, far-red or polarized signals. However, the question remains as to whether humans are failing to detect the bulk of color variation in the visible range.</p> <p>Bergeron and Fuller addressed this question by using a methodology that should be flawed by human subjectivity and comparing it to a methodology that is free of human perceptual biases. They compared the coloration of bird specimens from a museum with the coloration of bird images from a field guide (see image at right). They found that field guide images detected the vast majority of the variation in coloration that was present in the museum specimens. This means that human vision detects the major patterns in coloration in the visible range. Human vision cannot be used to say which color patterns are more or less conspicuous to another species, but it can be used to detect major patterns in animal coloration in the visible spectrum in nature. </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;">A</span>ssessing variation in animal coloration is difficult as animals differ in their visual system properties. This has led some to propose that human vision can never be used to evaluate coloration, yet many studies have a long history of relying on human vision. To reconcile these views, we compared the reflectance spectra of preserved avian plumage elements with two measures that are humans biased: RGB values from digital photographs and the corresponding reflectance spectra from a field guide. We measured 73 plumage elements across 14 bird species. The field guide reflectance spectra were drastically different from that of the actual birds, particularly for blue elements. However, principal components analyses on all three data sets indicated remarkably similar data structure. We conclude that human vision can detect much of the variation in coloration in the visible range, providing fodder for subsequent studies in ecology, evolution, behavior, and visual ecology. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695282">Read&nbsp;the&nbsp;Article</a></p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “A migratory divide in the Painted Bunting (Passerina ciris)” http://amnat.org/an/newpapers/FebBattey.html The DOI will be http://dx.doi.org/10.1086/695439 Genomic data maps migration in a songbird and confirms a 66-yr-old hypothesis of trans-gulf migration Every spring, temperate North America welcomes the arrival of one of the continent’s most striking songbirds, the Painted Bunting, to their breeding grounds in northern Mexico and the Southeastern US. What we haven’t known, until recently, is exactly where they’re coming from. Now researchers at the University of Washington and Burke Museum of Natural History have used genetic data to map the annual migration of the species, and discovered an unexpected difference in the flight paths of populations in Texas and Louisiana. The team, working in the lab of Burke Museum Curator of Ornithology John Klicka, sequenced DNA and took measurements of the size and shape of Painted Buntings caught both while breeding and while overwintering. With these data, they used mathematical models to identify groups of individuals that share a recent common ancestor, drawing links between different parts of the species’ two seasonal ranges. The researchers found that breeding birds in Louisiana are closely related to wintering birds from the Yucat&aacute;n Peninsula; meanwhile, breeding populations in Texas, Kansas, and Oklahoma match wintering samples from western and central Mexico. Breeding birds from the Atlantic Coast, meanwhile, appear to winter only in Florida, the Bahamas, and Cuba, and rarely interbreed with other populations. The data provides the first evidence that Painted Buntings using different migratory routes are also genetically differentiated, thus shedding light on how seasonal migration shapes the evolution of songbirds. Additionally, they show that declining populations along the Atlantic Coast and in the Mississippi River Valley are unique in both their genes and their life history, and should be treated as independent units by conservationists looking to preserve this iconic species. Abstract In the Painted Bunting (Passerina ciris), a North American songbird, populations on the Atlantic coast and interior southern United States are known to be allopatric during the breeding season, but efforts to map connectivity with wintering ranges have been largely inconclusive. Using genomic and morphological data from museum specimens and banded birds, we found evidence of three genetically differentiated Painted Bunting populations with distinct wintering ranges and molt-migration phenologies. In addition to confirming that the Atlantic coast population remains allopatric throughout the annual cycle, we identified an unexpected migratory divide within the interior breeding range. Populations breeding in Louisiana winter on the Yucatán Peninsula, and are parapatric with other interior populations that winter in mainland Mexico and Central America. Across the interior breeding range, genetic ancestry is also associated with variation in wing length, suggesting that selection may be promoting morphological divergence in populations with different migration strategies. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695439 </i></p> <p><b>Genomic data maps migration in a songbird and confirms a 66-yr-old hypothesis of trans-gulf migration </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;">E</span>very spring, temperate North America welcomes the arrival of one of the continent&rsquo;s most striking songbirds, the Painted Bunting, to their breeding grounds in northern Mexico and the Southeastern US. What we haven&rsquo;t known, until recently, is exactly where they&rsquo;re coming from. Now researchers at the University of Washington and Burke Museum of Natural History have used genetic data to map the annual migration of the species, and discovered an unexpected difference in the flight paths of populations in Texas and Louisiana. The team, working in the lab of Burke Museum Curator of Ornithology John Klicka, sequenced DNA and took measurements of the size and shape of Painted Buntings caught both while breeding and while overwintering. With these data, they used mathematical models to identify groups of individuals that share a recent common ancestor, drawing links between different parts of the species&rsquo; two seasonal ranges. The researchers found that breeding birds in Louisiana are closely related to wintering birds from the Yucat&aacute;n Peninsula; meanwhile, breeding populations in Texas, Kansas, and Oklahoma match wintering samples from western and central Mexico. Breeding birds from the Atlantic Coast, meanwhile, appear to winter only in Florida, the Bahamas, and Cuba, and rarely interbreed with other populations. The data provides the first evidence that Painted Buntings using different migratory routes are also genetically differentiated, thus shedding light on how seasonal migration shapes the evolution of songbirds. Additionally, they show that declining populations along the Atlantic Coast and in the Mississippi River Valley are unique in both their genes and their life history, and should be treated as independent units by conservationists looking to preserve this iconic 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;">I</span>n the Painted Bunting (<i>Passerina ciris</i>), a North American songbird, populations on the Atlantic coast and interior southern United States are known to be allopatric during the breeding season, but efforts to map connectivity with wintering ranges have been largely inconclusive. Using genomic and morphological data from museum specimens and banded birds, we found evidence of three genetically differentiated Painted Bunting populations with distinct wintering ranges and molt-migration phenologies. In addition to confirming that the Atlantic coast population remains allopatric throughout the annual cycle, we identified an unexpected migratory divide within the interior breeding range. Populations breeding in Louisiana winter on the Yucatán Peninsula, and are parapatric with other interior populations that winter in mainland Mexico and Central America. Across the interior breeding range, genetic ancestry is also associated with variation in wing length, suggesting that selection may be promoting morphological divergence in populations with different migration strategies. </p> <!-- <p> <!-- <a href="http://dx.doi.org/10.1086/695439">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Offspring size and reproductive allocation in harvester ants” http://amnat.org/an/newpapers/JanWiernasz.html READ THE PAPER: http://dx.doi.org/10.1086/694903 Taking the Trivers-Willard hypothesis beyond mammals, researchers find that ant colonies invest differently in queens and males When organisms reproduce, they must distribute resources among their offspring. How many offspring should be produced? How big should they be? Should the number of females be the same as the number of males? Should similar amounts of resources be invested in females and males or should one sex receive preferential investment? Diane Wiernasz and Blaine Cole (University of Houston, Houston, TX) address these questions in Western Harvester Ants, using information from an experiment on more than 200 ant colonies, part of their long-term study population near Grand Junction, CO. Harvester ants collect and store the seeds of local plants to use as food. Both male and female offspring are more successful when they are larger, but small size has greater negative effects on daughters. In a field experiment, when colonies are given additional food that they can store, they make more of both male and females; colonies benefit the most from producing more offspring of both sexes. However, colonies given extra food that cannot be stored make larger males but not larger females. Colonies appear to have an "invest in females first" strategy, and always make females that are relatively large. When food is limited, resources are used preferentially to make large daughters and what is left is invested in sons. The mathematical model developed in this study successfully extends the classic work of Trivers and Willard to show how parents that produce multiple offspring should invest in females vs. males based not only on parental resources but on the benefits that increased investment will provide to offspring of each sex. More forthcoming papers &raquo; <p style="text-align: right;"><i>READ THE PAPER: <a href="http://dx.doi.org/10.1086/694903">http://dx.doi.org/10.1086/694903 </a></i></p> <p><b>Taking the Trivers-Willard hypothesis beyond mammals, researchers find that ant colonies invest differently in queens and males </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">W</span>hen organisms reproduce, they must distribute resources among their offspring. How many offspring should be produced? How big should they be? Should the number of females be the same as the number of males? Should similar amounts of resources be invested in females and males or should one sex receive preferential investment? Diane Wiernasz and Blaine Cole (University of Houston, Houston, TX) address these questions in Western Harvester Ants, using information from an experiment on more than 200 ant colonies, part of their long-term study population near Grand Junction, CO. Harvester ants collect and store the seeds of local plants to use as food.</p> <p>Both male and female offspring are more successful when they are larger, but small size has greater negative effects on daughters. In a field experiment, when colonies are given additional food that they can store, they make more of both male and females; colonies benefit the most from producing more offspring of both sexes. However, colonies given extra food that cannot be stored make larger males but not larger females. Colonies appear to have an &quot;invest in females first&quot; strategy, and always make females that are relatively large. When food is limited, resources are used preferentially to make large daughters and what is left is invested in sons. The mathematical model developed in this study successfully extends the classic work of Trivers and Willard to show how parents that produce multiple offspring should invest in females vs. males based not only on parental resources but on the benefits that increased investment will provide to offspring of each sex. <!-- <a href="http://dx.doi.org/10.1086/694903">Read&nbsp;the&nbsp;Article</a> --> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Patterns of local community composition are linked to large-scale diversification and dispersal of clades” http://amnat.org/an/newpapers/FebWiens.html The DOI will be http://dx.doi.org/10.1086/695495 Local communities are dominated by clades with rapid rates of global-scale diversification and dispersal What determines which groups of organisms will have the most species at any location on Earth? Few studies, if any, have addressed this fundamental question. A new study suggests there is a simple explanation for these patterns of diversity. A new paper in The&nbsp;American Naturalist addresses the question of which groups dominate local communities, by analyzing data from snakes. The study used data from 166 local sites around the world and an evolutionary tree of 1,262 snake species. The results reveal that those groups that evolve new species most rapidly and spread most quickly are those that dominate most local communities around the world. On the other hand, groups that are present in a region longer than others rarely dominate local communities, despite having more time to build up species diversity. The results also reveal that most snake communities around the world are surprisingly similar to each other. Specifically, most communities are dominated by members of one family (Colubridae), which includes garter snakes and kingsnakes. Most communities also have dangerously venomous species from the viper family and the cobra family. Remarkably, these venomous groups have spread around the world almost as much as the highly successful Colubridae have, but generally have few species in local communities. The results suggest that these dangerously venomous snakes may be weaker competitors relative to species of the mostly harmless Colubridae. The tendency for local communities to be dominated by a few groups that proliferate and spread rapidly may apply to many other organisms besides snakes. For example, plants, frogs, mammals, and birds are each dominated by a rapidly proliferating group that has spread around the world. The new study proposes that there may be simple explanation for patterns of local species diversity across organisms and around the world. Abstract At any location, a group of organisms may be represented by several clades. What determines which clades will dominate local communities in terms of their species richness? Here, this relatively neglected question is addressed by analyzing 166 local assemblages of snakes distributed globally. For most regions, local assemblages are dominated by clades with higher global-scale diversification rates and more frequent dispersal into each region, and not by clades that have been present in that region longer. This result contrasts with many other studies of local richness (in other organisms), which show strong impacts of regional colonization time on overall local species richness of clades. Furthermore, even though local assemblages are assembled independently on different continents, most regions have converged on similar patterns of proportional richness. Specifically, a few rapidly diversifying clades dominate most communities around the world. The high diversification rates of these clades are then linked to their high dispersal rates. Similar patterns may occur in many groups, such as plants, frogs, salamanders, birds, and mammals. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695495 </i></p> <p><b>Local communities are dominated by clades with rapid rates of global-scale diversification and dispersal </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 determines which groups of organisms will have the most species at any location on Earth? Few studies, if any, have addressed this fundamental question. A new study suggests there is a simple explanation for these patterns of diversity. </p><p>A new paper in <i>The&nbsp;American Naturalist</i> addresses the question of which groups dominate local communities, by analyzing data from snakes. The study used data from 166 local sites around the world and an evolutionary tree of 1,262 snake species. The results reveal that those groups that evolve new species most rapidly and spread most quickly are those that dominate most local communities around the world. On the other hand, groups that are present in a region longer than others rarely dominate local communities, despite having more time to build up species diversity. </p><p>The results also reveal that most snake communities around the world are surprisingly similar to each other. Specifically, most communities are dominated by members of one family (Colubridae), which includes garter snakes and kingsnakes. Most communities also have dangerously venomous species from the viper family and the cobra family. Remarkably, these venomous groups have spread around the world almost as much as the highly successful Colubridae have, but generally have few species in local communities. The results suggest that these dangerously venomous snakes may be weaker competitors relative to species of the mostly harmless Colubridae. </p><p>The tendency for local communities to be dominated by a few groups that proliferate and spread rapidly may apply to many other organisms besides snakes. For example, plants, frogs, mammals, and birds are each dominated by a rapidly proliferating group that has spread around the world. The new study proposes that there may be simple explanation for patterns of local species diversity across organisms and around the world.</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>t any location, a group of organisms may be represented by several clades. What determines which clades will dominate local communities in terms of their species richness? Here, this relatively neglected question is addressed by analyzing 166 local assemblages of snakes distributed globally. For most regions, local assemblages are dominated by clades with higher global-scale diversification rates and more frequent dispersal into each region, and not by clades that have been present in that region longer. This result contrasts with many other studies of local richness (in other organisms), which show strong impacts of regional colonization time on overall local species richness of clades. Furthermore, even though local assemblages are assembled independently on different continents, most regions have converged on similar patterns of proportional richness. Specifically, a few rapidly diversifying clades dominate most communities around the world. The high diversification rates of these clades are then linked to their high dispersal rates. Similar patterns may occur in many groups, such as plants, frogs, salamanders, birds, and mammals.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/695495">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Seasonal food scarcity prompts long-distance foraging by a wild social bee” http://amnat.org/an/newpapers/JanPope.html The DOI will be http://dx.doi.org/10.1086/694843 Seasonal food scarcity prompts long-distance foraging by a wild social bee Across the globe, pollinating insects are essential for the persistence of plant communities and provide services that are critical for the production of many crops, worth an estimated $200 billion globally in enhanced yields each year. Bees—a large and diverse group of insects that primarily depend on pollen and nectar from flowering plants—are some of the most widespread and effective pollinators. Despite their ubiquity and importance to humans, little is known about the spatial range at which wild bees forage for food, or how they alter their behavior in landscapes where flowering plant density shifts across the year. This is due, in part, to the difficulties of tracking the movements of flying insects in the wild. In this study, graduate student Nathaniel Pope and Dr. Shalene Jha from the University of Texas at Austin collected wild bumble bees and used genetic markers to identify sister bees as they foraged across multiple landscapes in the chaparral of central California. Using the bees’ genetic information, Pope and Jha mapped out the foraging patterns of each colony across different time periods. They found that bumble bees are more sophisticated foragers than previously expected; bumble bees choose to fly longer distances to reach higher density patches of flowers, but only in the summer months when flowering resources are more limited. Overall, the results from the study suggest that potential alterations to plant flowering due to global change could dramatically alter bumble bee movement and pollination services. Further, the research suggests that current pollinator conservation efforts should consider targeting late-season floral resources, when bees may be most stressed by long-distance foraging. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/694843 </i></p> <p><b>Seasonal food scarcity prompts long-distance foraging by a wild social bee </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>cross the globe, pollinating insects are essential for the persistence of plant communities and provide services that are critical for the production of many crops, worth an estimated $200 billion globally in enhanced yields each year. Bees&mdash;a large and diverse group of insects that primarily depend on pollen and nectar from flowering plants&mdash;are some of the most widespread and effective pollinators. Despite their ubiquity and importance to humans, little is known about the spatial range at which wild bees forage for food, or how they alter their behavior in landscapes where flowering plant density shifts across the year. This is due, in part, to the difficulties of tracking the movements of flying insects in the wild.</p> <p>In this study, graduate student Nathaniel Pope and Dr. Shalene Jha from the University of Texas at Austin collected wild bumble bees and used genetic markers to identify sister bees as they foraged across multiple landscapes in the chaparral of central California. Using the bees&rsquo; genetic information, Pope and Jha mapped out the foraging patterns of each colony across different time periods. They found that bumble bees are more sophisticated foragers than previously expected; bumble bees choose to fly longer distances to reach higher density patches of flowers, but only in the summer months when flowering resources are more limited. Overall, the results from the study suggest that potential alterations to plant flowering due to global change could dramatically alter bumble bee movement and pollination services. Further, the research suggests that current pollinator conservation efforts should consider targeting late-season floral resources, when bees may be most stressed by long-distance foraging.<!-- <a href="http://dx.doi.org/10.1086/694843">Read&nbsp;the&nbsp;Article</a> --> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Multilevel selection in the filamentous ascomycete Neurospora tetrasperma” http://amnat.org/an/newpapers/MarMeunier.html The DOI will be http://dx.doi.org/10.1086/695803 This paper experimentally shows an ongoing transition in individuality in a fungus An individual defines a single, separate organism distinguished from others of the same kind. Throughout the evolution of life, there have been transitions in individuality when autonomous entities have grouped together to form new, higher-level individuals. Examples of such transitions are when genes grouped to form genomes, cells to form bodies, and organisms to form societies. Theoretical expectations during transitions in individuality are well defined. Most importantly, grouping has to yield benefits, arising e.g. from cooperation amongst lower levels of the group. At the same time, conflicts between members of the group may arise and should be minimized, e.g. in ensuring genetic homogeneity inside of the group. Divergence from the inside would mean that selfish variants, deleterious to the group-level could invade and take over, which is what happens, for example, in cancers. The researchers, all female scientists from Uppsala University in Sweden, investigated pros and cons of a transition in individuality in Fungi, a group where individuality has been a long-standing issue. They postulated that their model, Neurospora tetrasperma, is undergoing a transition in individuality. In this species, two different levels of individuals exist: the nucleus and the mycelium. Cooperation and/or conflicts may be expected among differing nuclei that could benefit or harm the mycelium, respectively. The researchers investigated how the nuclear ratio between the two types varied in different conditions, and how fitness was impacted by changes in nuclear ratios. The nuclei had complementary traits, consistent with cooperation and division of labor. However, they also verified the existence of conflicts at the nuclear level: in one lineage, one type of nucleus replicated and transmitted better, yet had a negative impact on the mycelium fitness. Heterokaryosis in N.&nbsp;tetrasperma thus exemplifies a genetic system where transition in individuality seems at the same time advantageous and incomplete. Abstract The history of life has been driven by evolutionary transitions in individuality, i.e., the aggregation of autonomous individuals to form a new, higher-level individual. The fungus Neurospora tetrasperma has recently undergone an evolutionary transition in individuality from homokaryosis (one single type of nuclei in the same cytoplasm) to heterokaryosis (two genetically divergent and free-ranging nuclear types). In this species, selection can act at different levels: while nuclei can compete in their replication and transmission into short-lived asexual spores, at the level of the heterokaryotic individual cooperation between nuclear types is required to produce the long-lived sexual spores. Conflicts can arise between these two levels of selection if the coevolution between nuclear types is disrupted. Here, we investigated the extent of multilevel selection in three strains of N.&nbsp;tetrasperma. We assessed the ratio between nuclear types under different conditions, and measured fitness traits of homo- and heterokaryotic mycelia with varying nuclear ratios. We show that the two nuclei have complementary traits, consistent with division of labor and cooperation. In one strain, for which a recent chromosomal introgression was detected, we observed the occurrence of selfish nuclei, enjoying better replication and transmission than sister nuclei at the same time as being detrimental to the heterokaryon. We hypothesize that introgression has disrupted the coevolution between nuclear types in this strain. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695803 </i></p> <p><b>This paper experimentally shows an ongoing transition in individuality in a fungus </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>n individual defines a single, separate organism distinguished from others of the same kind. Throughout the evolution of life, there have been transitions in individuality when autonomous entities have grouped together to form new, higher-level individuals. Examples of such transitions are when genes grouped to form genomes, cells to form bodies, and organisms to form societies. Theoretical expectations during transitions in individuality are well defined. Most importantly, grouping has to yield benefits, arising e.g. from cooperation amongst lower levels of the group. At the same time, conflicts between members of the group may arise and should be minimized, e.g. in ensuring genetic homogeneity inside of the group. Divergence from the inside would mean that selfish variants, deleterious to the group-level could invade and take over, which is what happens, for example, in cancers. The researchers, all female scientists from Uppsala University in Sweden, investigated pros and cons of a transition in individuality in Fungi, a group where individuality has been a long-standing issue. They postulated that their model, <i>Neurospora tetrasperma</i>, is undergoing a transition in individuality. In this species, two different levels of individuals exist: the nucleus and the mycelium. Cooperation and/or conflicts may be expected among differing nuclei that could benefit or harm the mycelium, respectively. The researchers investigated how the nuclear ratio between the two types varied in different conditions, and how fitness was impacted by changes in nuclear ratios. The nuclei had complementary traits, consistent with cooperation and division of labor. However, they also verified the existence of conflicts at the nuclear level: in one lineage, one type of nucleus replicated and transmitted better, yet had a negative impact on the mycelium fitness. Heterokaryosis in <i>N.&nbsp;tetrasperma</i> thus exemplifies a genetic system where transition in individuality seems at the same time advantageous and incomplete. </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he history of life has been driven by evolutionary transitions in individuality, i.e., the aggregation of autonomous individuals to form a new, higher-level individual. The fungus <i>Neurospora tetrasperma </i>has recently undergone an evolutionary transition in individuality from homokaryosis (one single type of nuclei in the same cytoplasm) to heterokaryosis (two genetically divergent and free-ranging nuclear types). In this species, selection can act at different levels: while nuclei can compete in their replication and transmission into short-lived asexual spores, at the level of the heterokaryotic individual cooperation between nuclear types is required to produce the long-lived sexual spores. Conflicts can arise between these two levels of selection if the coevolution between nuclear types is disrupted. Here, we investigated the extent of multilevel selection in three strains of <i>N.&nbsp;tetrasperma</i>. We assessed the ratio between nuclear types under different conditions, and measured fitness traits of homo- and heterokaryotic mycelia with varying nuclear ratios. We show that the two nuclei have complementary traits, consistent with division of labor and cooperation. In one strain, for which a recent chromosomal introgression was detected, we observed the occurrence of selfish nuclei, enjoying better replication and transmission than sister nuclei at the same time as being detrimental to the heterokaryon. We hypothesize that introgression has disrupted the coevolution between nuclear types in this strain. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695803">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Testing range-limit hypotheses using range-wide habitat suitability and occupancy for the scarlet monkeyflower (Erythranthe cardinalis)” http://amnat.org/an/newpapers/MarAngert-A.html The DOI will be http://dx.doi.org/10.1086/695984 Abstract Determining the causes of geographic range limits is a fundamental problem in ecology, evolution, and conservation biology. Range limits arise due to fitness and dispersal limitation, which yield contrasting predictions about habitat suitability and occupancy of suitable habitat across geographic ranges. If a range edge is limited primarily by fitness, occupancy of suitable habitat should be high, habitat suitability should decline towards the edge, and no suitable habitat should exist beyond it. In contrast, a range edge limited primarily by dispersal should have unoccupied but suitable habitat at and beyond the edge. We built ecological niche models relating occurrence records for the scarlet monkeyflower (Erythranthe cardinalis) to climatic variables, and applied these models to independent data from systematic, range-wide surveys of presence and absence to estimate the availability and occupancy of climatically suitable habitat. We found that fitness limitation predominated over dispersal limitation, but dispersal limitation also played a role at the poleward edge. These results are consistent with the hypothesis that dispersal limitation is more important along shallow environmental gradients and also suggest that synergy between dispersal and fitness limitation can contribute to colonization failure. The framework used here is validated by independent data and could be readily applied to inferring causes of range limits in many other species. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695984 </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;">D</span>etermining the causes of geographic range limits is a fundamental problem in ecology, evolution, and conservation biology. Range limits arise due to fitness and dispersal limitation, which yield contrasting predictions about habitat suitability and occupancy of suitable habitat across geographic ranges. If a range edge is limited primarily by fitness, occupancy of suitable habitat should be high, habitat suitability should decline towards the edge, and no suitable habitat should exist beyond it. In contrast, a range edge limited primarily by dispersal should have unoccupied but suitable habitat at and beyond the edge. We built ecological niche models relating occurrence records for the scarlet monkeyflower (<i>Erythranthe cardinalis</i>) to climatic variables, and applied these models to independent data from systematic, range-wide surveys of presence and absence to estimate the availability and occupancy of climatically suitable habitat. We found that fitness limitation predominated over dispersal limitation, but dispersal limitation also played a role at the poleward edge. These results are consistent with the hypothesis that dispersal limitation is more important along shallow environmental gradients and also suggest that synergy between dispersal and fitness limitation can contribute to colonization failure. The framework used here is validated by independent data and could be readily applied to inferring causes of range limits in many other species.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695984">Read&nbsp;the&nbsp;Article</a></p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Partitioning the effects of eco-evolutionary feedbacks on community stability” http://amnat.org/an/newpapers/MarPatel.html The DOI will be http://dx.doi.org/10.1086/695834 Natural communities are perpetually subject to disturbances in their environment. Do communities recover from these perturbations or might species be lost? Communities may respond to disturbances in two ways: through an ecological response (species densities may change) and through an evolutionary response (species may adapt to new conditions). Swati Patel, from Tulane University, and co-authors Michael Cortez and Sebastian Schreiber explore how these two responses, in some cases, work together to maintain stable communities, and in others, drive instability that may lead to the loss of species. Using mathematical models, they develop a simple and general formula that predicts whether a community is able to recover or not following an environmental disturbance. Importantly, they find that this depends on how quickly species can evolve relative to how quickly their densities change. Surprisingly, faster evolution does not necessarily imply more stable communities; communities with more rapidly evolving species can actually be more prone to species loss! Abstract A&nbsp;fundamental challenge in ecology continues to be identifying mechanisms that stabilize community dynamics. By altering the interactions within a community, eco-evolutionary feedbacks may play a role in community stability. Indeed, recent empirical and theoretical studies demonstrate that these feedbacks can stabilize or destabilize communities, and moreover, that this sometimes depends on the relative rate of ecological to evolutionary processes. So far, theory on how eco-evolutionary feedbacks impact stability exists only for a few special cases. In our work, we develop a general theory for determining the effects of eco-evolutionary feedbacks on stability in communities with an arbitrary number of interacting species and evolving traits for when evolution is slow and fast. We characterize how eco-evolutionary feedbacks lead to stable communities that would otherwise be unstable, and vice versa. Additionally, we show how one can identify the roles of direct and indirect feedbacks between ecological and evolutionary processes on stability, and how the effects of those feedbacks depend on the rate of evolution relative to the ecological time scales. Applying our methods to models of competing species and food chains, we demonstrate how the functional form of trade offs, genetic correlations between traits, and the rate of evolution determine whether eco-evolutionary feedbacks stabilize or destabilize communities. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695834 </i></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;">N</span>atural communities are perpetually subject to disturbances in their environment. Do communities recover from these perturbations or might species be lost? Communities may respond to disturbances in two ways: through an ecological response (species densities may change) and through an evolutionary response (species may adapt to new conditions). Swati Patel, from Tulane University, and co-authors Michael Cortez and Sebastian Schreiber explore how these two responses, in some cases, work together to maintain stable communities, and in others, drive instability that may lead to the loss of species. Using mathematical models, they develop a simple and general formula that predicts whether a community is able to recover or not following an environmental disturbance. Importantly, they find that this depends on how quickly species can evolve relative to how quickly their densities change. Surprisingly, faster evolution does not necessarily imply more stable communities; communities with more rapidly evolving species can actually be more prone to species loss!</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;fundamental challenge in ecology continues to be identifying mechanisms that stabilize community dynamics. By altering the interactions within a community, eco-evolutionary feedbacks may play a role in community stability. Indeed, recent empirical and theoretical studies demonstrate that these feedbacks can stabilize or destabilize communities, and moreover, that this sometimes depends on the relative rate of ecological to evolutionary processes. So far, theory on how eco-evolutionary feedbacks impact stability exists only for a few special cases. In our work, we develop a general theory for determining the effects of eco-evolutionary feedbacks on stability in communities with an arbitrary number of interacting species and evolving traits for when evolution is slow and fast. We characterize how eco-evolutionary feedbacks lead to stable communities that would otherwise be unstable, and vice versa. Additionally, we show how one can identify the roles of direct and indirect feedbacks between ecological and evolutionary processes on stability, and how the effects of those feedbacks depend on the rate of evolution relative to the ecological time scales. Applying our methods to models of competing species and food chains, we demonstrate how the functional form of trade offs, genetic correlations between traits, and the rate of evolution determine whether eco-evolutionary feedbacks stabilize or destabilize communities.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695834">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Towards a mechanistic understanding of thermal niche partitioning” http://amnat.org/an/newpapers/MarSmith-A.html The DOI will be http://dx.doi.org/10.1086/695805 Abstract We develop a theoretical framework to elucidate the mechanistic basis of thermal niche partitioning in ectotherms. Using a food web module of two consumers competing for a biotic resource, we investigate how temperature effects on species&#39; attack and mortality rates scale up to population-level outcomes of coexistence and exclusion. We find that differences between species in their competitive effects ultimately arise from asymmetries generated by the non-linear nature of the temperature response of mortality: cold-adapted species, and thermal specialists, limit themselves more strongly than they limit their warm-adapted, and generalist, competitors. These asymmetries become greater as seasonal temperature fluctuations increase, generating latitudinal variation in coexistence patterns and priority effects. Characterizing species&#39; thermal niches in terms of mechanistic descriptions of trait responses to temperature allows us to make testable predictions about the population-level outcomes of competition based solely on three fundamental, and easily measurable, quantities: attack rate optima, response breadths and temperature sensitivity of mortality. We validate our framework by testing its predictions with data from an insect host-parasitoid community. Simply by quantifying the three basic quantities we predict that priority effects cannot occur in this system, which is borne out by population-level experiments showing that the outcome of competition does not depend on initial conditions. More broadly, our framework can predict the conditions under which exotic invasive species can exclude, or coexist with, native biota, and the effects of climate warming on competitive communities across latitudinal gradients. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695805 </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;">W</span>e develop a theoretical framework to elucidate the mechanistic basis of thermal niche partitioning in ectotherms. Using a food web module of two consumers competing for a biotic resource, we investigate how temperature effects on species&#39; attack and mortality rates scale up to population-level outcomes of coexistence and exclusion. We find that differences between species in their competitive effects ultimately arise from asymmetries generated by the non-linear nature of the temperature response of mortality: cold-adapted species, and thermal specialists, limit themselves more strongly than they limit their warm-adapted, and generalist, competitors. These asymmetries become greater as seasonal temperature fluctuations increase, generating latitudinal variation in coexistence patterns and priority effects. Characterizing species&#39; thermal niches in terms of mechanistic descriptions of trait responses to temperature allows us to make testable predictions about the population-level outcomes of competition based solely on three fundamental, and easily measurable, quantities: attack rate optima, response breadths and temperature sensitivity of mortality. We validate our framework by testing its predictions with data from an insect host-parasitoid community. Simply by quantifying the three basic quantities we predict that priority effects cannot occur in this system, which is borne out by population-level experiments showing that the outcome of competition does not depend on initial conditions. More broadly, our framework can predict the conditions under which exotic invasive species can exclude, or coexist with, native biota, and the effects of climate warming on competitive communities across latitudinal gradients.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/695805">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Evolution as a coexistence mechanism: Does genetic architecture matter?” http://amnat.org/an/newpapers/MarSchreiber.html The DOI will be http://dx.doi.org/10.1086/695832 Synergistic pleitropy and dominance in defensive alleles promote polymorphic prey and predator coexistence A&nbsp;fundamental principle in ecology is the competitive exclusion principle. Like two gladiatorial combatants in the Colosseum, this principle asserts that when two species compete for a single resource, one species will be driven extinct (the loser) and one will persist (the winner). Competition for resources, whether that be pathogens competing for hosts, herbivores competing for plants, or predators competing for prey, is ubiquitous in nature. Yet many of these competing species coexist. How can this be? Using mathematical models, Sebastian Schreiber, a Professor of Evolution and Ecology at the University of California, Davis, and his co-authors show that evolution of defenses by the exploited species provides one possible answer. This new coexistence mechanism requires that genotypes defended against one of the competitors are poorly defended against the other competitor. This trade-off can lead to a complicated rock-paper-scissor dynamic, in which no resource genotype or competitor ever has the upper hand against everybody else. Namely, when one competitor is more abundant in the system, the genotype best defended against this competitor becomes abundant. Unable to exploit this well defended genotype, this competitor species decreases in abundance as the other competitor becomes more common. Thus, the cycle continues as the genotype best defended against this other competitor becomes more abundant. Whether this mechanism is effective for enabling coexistence, however, depends on the details of the genetics underlying the defensive trait. In light of recent empirical evidence that evolution can occur quickly, the work of Schreiber and colleagues raises the tantalizing possibility that species may coexist due to the evolution of others rather than evolution of their own traits. Abstract Species sharing a prey or a predator species may go extinct due to exploitative or apparent competition. We examine whether evolution of the shared species acts as a coexistence mechanism and to what extent the answer depends on the genetic architecture underlying trait evolution. In our models of exploitative and apparent competition, the shared species evolves its defense or prey use. Evolving species are either haploid or diploid. A single locus pleiotropically determines prey nutritional quality and predator attack rates. When pleiotropy is sufficiently antagonistic (e.g. nutritional prey are harder to capture), eco-evolutionary assembly culminates in one of two stable states supporting only two species. When pleiotropy is weakly antagonistic or synergistic, assembly is intransitive: species-genotype pairs are cyclically displaced by rare invasions of the missing genotypes or species. This intransitivity allows for coexistence if, along its equilibria, the geometric mean of recovery rates exceeds the geometric mean of loss rates of the rare genotypes or species. By affecting these rates, synergistic pleiotropy can mediate coexistence, while antagonistic pleiotropy does not. For diploid populations experiencing weak antagonistic pleiotropy, superadditive allelic contributions to fitness can mitigate coexistence via an eco-evolutionary storage effect. Density-dependence and mutations also promote coexistence. These results highlight how the efficacy of evolution as a coexistence mechanism may depend on the underlying genetic architecture. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695832 </i></p> <p><b>Synergistic pleitropy and dominance in defensive alleles promote polymorphic prey and predator coexistence </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>&nbsp;fundamental principle in ecology is the competitive exclusion principle. Like two gladiatorial combatants in the Colosseum, this principle asserts that when two species compete for a single resource, one species will be driven extinct (the loser) and one will persist (the winner). Competition for resources, whether that be pathogens competing for hosts, herbivores competing for plants, or predators competing for prey, is ubiquitous in nature. Yet many of these competing species coexist. How can this be? Using mathematical models, Sebastian Schreiber, a Professor of Evolution and Ecology at the University of California, Davis, and his co-authors show that evolution of defenses by the exploited species provides one possible answer. This new coexistence mechanism requires that genotypes defended against one of the competitors are poorly defended against the other competitor. This trade-off can lead to a complicated rock-paper-scissor dynamic, in which no resource genotype or competitor ever has the upper hand against everybody else. Namely, when one competitor is more abundant in the system, the genotype best defended against this competitor becomes abundant. Unable to exploit this well defended genotype, this competitor species decreases in abundance as the other competitor becomes more common. Thus, the cycle continues as the genotype best defended against this other competitor becomes more abundant. Whether this mechanism is effective for enabling coexistence, however, depends on the details of the genetics underlying the defensive trait. In light of recent empirical evidence that evolution can occur quickly, the work of Schreiber and colleagues raises the tantalizing possibility that species may coexist due to the evolution of others rather than evolution of their own traits.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>pecies sharing a prey or a predator species may go extinct due to exploitative or apparent competition. We examine whether evolution of the shared species acts as a coexistence mechanism and to what extent the answer depends on the genetic architecture underlying trait evolution. In our models of exploitative and apparent competition, the shared species evolves its defense or prey use. Evolving species are either haploid or diploid. A single locus pleiotropically determines prey nutritional quality and predator attack rates. When pleiotropy is sufficiently antagonistic (e.g. nutritional prey are harder to capture), eco-evolutionary assembly culminates in one of two stable states supporting only two species. When pleiotropy is weakly antagonistic or synergistic, assembly is intransitive: species-genotype pairs are cyclically displaced by rare invasions of the missing genotypes or species. This intransitivity allows for coexistence if, along its equilibria, the geometric mean of recovery rates exceeds the geometric mean of loss rates of the rare genotypes or species. By affecting these rates, synergistic pleiotropy can mediate coexistence, while antagonistic pleiotropy does not. For diploid populations experiencing weak antagonistic pleiotropy, superadditive allelic contributions to fitness can mitigate coexistence via an eco-evolutionary storage effect. Density-dependence and mutations also promote coexistence. These results highlight how the efficacy of evolution as a coexistence mechanism may depend on the underlying genetic architecture. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695832">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Evolution in a community context: trait responses to multiple species interactions” http://amnat.org/an/newpapers/Mar-terHorst.html The DOI will be http://dx.doi.org/10.1086/695835 Evolution in a community context limits adaptation to any single species, but results in adaptation to communities Imagine if somebody tried to describe your personality based only on your interactions with one person. It would be nearly impossible because you interact with many different people, each in a different way. Moreover, you might interact with your parent differently when your partner is present, or when your whole family is present. Much of our mechanistic understanding of how species evolve is based on controlled observations and experiments involving one species evolving in response to one another. Yet, species live in a world of complex interactions with many other species: predators, prey, competitors, herbivores, pollinators, and many more. To understand how species evolve in natural environments, we need to better understand how evolution in response to many species differs from evolution in response to just one other species. A recent review by Casey terHorst of California State University, Northridge, and colleagues highlights a number of reasons why it is important to consider so-called “evolution in a community context”. “Evolution becomes more difficult to predict when we start thinking about many species,” terHorst says, “because we have to think about all the indirect ways that they interact with each other.” Imagine trying to play rock-paper-scissors; there is no winning strategy. It gets even more complicated if you use a version popularized on The&nbsp;Big Bang Theory: rock-paper-scissor-lizard-Spock. We have to think about how genes are linked. For example, natural selection might favor plants with versions of genes that make flowers with more nectar, but that gene may be negatively linked to another one that produces chemicals to defend against herbivores and another that affects competitive ability. As terHorst says, “It’s certainly not simple to think about, but we’re starting with baby steps to understand what happens with just a little more complexity, with the hope of building up to more complex models.” Abstract Species that coexist in diverse natural communities interact in complex ways that alter each other’s abundances and affect selection on each other’s traits. Consequently, predicting trait evolution in natural communities may require understanding ecological and evolutionary dynamics involving a number of species. In August 2016, the American Society of Naturalists sponsored a symposium to explore evolution in a community context, focusing on microevolutionary processes. Here we provide an introduction to our perspectives on this topic by defining the context and describing some examples of when and how microevolutionary responses to multiple species may differ from evolution in isolation or in two-species communities. We find that indirect ecological and evolutionary effects can result in non-additive selection and evolution that cannot be predicted from pairwise interactions. Genetic correlations of ecological traits in one species can alter trait evolution and adaptation, as well as the abundances of other species. In general, evolution in multispecies communities can change ecological interactions, which then feed back to future evolutionary changes in ways that depend on these indirect effects. We suggest avenues for future research in this field, including determining the circumstances under which pairwise evolution does not adequately describe evolutionary trajectories. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695835 </i></p> <p><b>Evolution in a community context limits adaptation to any single species, but results in adaptation to communities </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>magine if somebody tried to describe your personality based only on your interactions with one person. It would be nearly impossible because you interact with many different people, each in a different way. Moreover, you might interact with your parent differently when your partner is present, or when your whole family is present. Much of our mechanistic understanding of how species evolve is based on controlled observations and experiments involving one species evolving in response to one another. Yet, species live in a world of complex interactions with many other species: predators, prey, competitors, herbivores, pollinators, and many more. To understand how species evolve in natural environments, we need to better understand how evolution in response to many species differs from evolution in response to just one other species. A recent review by Casey terHorst of California State University, Northridge, and colleagues highlights a number of reasons why it is important to consider so-called &ldquo;evolution in a community context&rdquo;. &ldquo;Evolution becomes more difficult to predict when we start thinking about many species,&rdquo; terHorst says, &ldquo;because we have to think about all the indirect ways that they interact with each other.&rdquo; Imagine trying to play rock-paper-scissors; there is no winning strategy. It gets even more complicated if you use a version popularized on <i>The&nbsp;Big Bang Theory</i>: rock-paper-scissor-lizard-Spock. We have to think about how genes are linked. For example, natural selection might favor plants with versions of genes that make flowers with more nectar, but that gene may be negatively linked to another one that produces chemicals to defend against herbivores and another that affects competitive ability. As terHorst says, &ldquo;It&rsquo;s certainly not simple to think about, but we&rsquo;re starting with baby steps to understand what happens with just a little more complexity, with the hope of building up to more complex models.&rdquo;</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;">S</span>pecies that coexist in diverse natural communities interact in complex ways that alter each other&rsquo;s abundances and affect selection on each other&rsquo;s traits. Consequently, predicting trait evolution in natural communities may require understanding ecological and evolutionary dynamics involving a number of species. In August 2016, the American Society of Naturalists sponsored a symposium to explore evolution in a community context, focusing on microevolutionary processes. Here we provide an introduction to our perspectives on this topic by defining the context and describing some examples of when and how microevolutionary responses to multiple species may differ from evolution in isolation or in two-species communities. We find that indirect ecological and evolutionary effects can result in non-additive selection and evolution that cannot be predicted from pairwise interactions. Genetic correlations of ecological traits in one species can alter trait evolution and adaptation, as well as the abundances of other species. In general, evolution in multispecies communities can change ecological interactions, which then feed back to future evolutionary changes in ways that depend on these indirect effects. We suggest avenues for future research in this field, including determining the circumstances under which pairwise evolution does not adequately describe evolutionary trajectories.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695835">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Multivariate climate change can favor large herbivore body size in food webs” http://amnat.org/an/newpapers/MarSmthRmsh.html The DOI will be http://dx.doi.org/10.1086/695768 Climate change may drive shifts towards larger herbivore body size Scientists have generally expected animals to get smaller as the planet warms, based on relationships between animal growth and development and temperature. However, global climate change means more than just warmer temperatures: other climate factors such as atmospheric carbon dioxide and rainfall patterns are also expected to change. Smith-Ramesh et al. have constructed a model based on food web interactions amongst old-field plants, grasshoppers, and spiders exposed to multiple changing climate variables. They find that under certain predicted future scenarios, climate change could actually result in larger animal body sizes. These results challenge past assumptions that climate change will result in smaller animals across the board. Abstract Climate change is expected to favor smaller-bodied organisms through effects of temperature on physiological performance and food-web interactions, so much so that smaller body size has been touted as a universal response to global warming alongside range-shifts and changing phenology. However, climate change involves more than warming. It is multivariate, and the interplay between climate variables may result in less straightforward predictions. We present a model that considers the simultaneous effect of multiple variables (temperature, CO2, and moisture) on herbivore body sizes within a tri-trophic food web comprised of vegetation, herbivores, and a shared predator. The model accounts for climate effects on animal behavior, plant and animal metabolism, and plant quality to explore emergent effects on herbivore body size. Our analysis reveals that some common multivariate climate change scenarios may favor larger-bodied herbivores, challenging previous findings of shifts toward small-bodied herbivores in the face of rising temperatures. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695768 </i></p> <p><b>Climate change may drive shifts towards larger herbivore body size </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>cientists have generally expected animals to get smaller as the planet warms, based on relationships between animal growth and development and temperature. However, global climate change means more than just warmer temperatures: other climate factors such as atmospheric carbon dioxide and rainfall patterns are also expected to change. Smith-Ramesh et al. have constructed a model based on food web interactions amongst old-field plants, grasshoppers, and spiders exposed to multiple changing climate variables. They find that under certain predicted future scenarios, climate change could actually result in larger animal body sizes. These results challenge past assumptions that climate change will result in smaller animals across the board.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>limate change is expected to favor smaller-bodied organisms through effects of temperature on physiological performance and food-web interactions, so much so that smaller body size has been touted as a universal response to global warming alongside range-shifts and changing phenology. However, climate change involves more than warming. It is multivariate, and the interplay between climate variables may result in less straightforward predictions. We present a model that considers the simultaneous effect of multiple variables (temperature, CO<span style="font-size:70%; position:relative; bottom:-0.3em;">2</span>, and moisture) on herbivore body sizes within a tri-trophic food web comprised of vegetation, herbivores, and a shared predator. The model accounts for climate effects on animal behavior, plant and animal metabolism, and plant quality to explore emergent effects on herbivore body size. Our analysis reveals that some common multivariate climate change scenarios may favor larger-bodied herbivores, challenging previous findings of shifts toward small-bodied herbivores in the face of rising temperatures. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695768">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Keystone individuals alter ecological and evolutionary consumer-resource dynamics” http://amnat.org/an/newpapers/FebStart.html The DOI will be http://dx.doi.org/10.1086/695322 A single individual with extreme traits changes populations, communities, and evolution Variation among organisms’ characteristics (traits), whether among species, populations, or individuals, forms a central pillar of both ecology and evolution. Recently, work in community ecology has suggested that differences among individuals and populations can have enormous consequences for where species are found, their abundances, and how they interact with other species in the community. However, these studies have invariably considered differences in traits among populations (mean difference) or variation within a population (variance difference). As a result, we lack an ecological or evolutionary answer to the idiom ‘can one person really make a difference?’. Put otherwise, can the addition or removal of one specific individual from a population have large and irreplaceable effects on the ecology and evolution of the system? Here, Denon Start (University of Toronto, ON, Canada) extends the keystone individual concept from behavioral ecology to encompass ecology and evolutionary biology. Applied to ecology and evolution, he defines the keystone individual concept as the idea that certain individuals, usually with extreme (unusual) trait values, have important consequences, and that replacing an extreme individual with a ‘normal’ individual would fundamentally change the ecological or evolutionary dynamics of the system. He then explores this concept at the Koffler Scientific Reserve in southern Ontario, using a gall-maker and its natural enemies. He shows that the presence of a single individual with an extreme predator-attracting phenotype increases mortality, changes the composition of predator communities, and increases selection for anti-predator traits in the surrounding gall-maker population. In short, the presence of a single individual with an extreme phenotype fundamentally changes the way the rest of the population interacts with other species, and the consequences of those interactions for selection. Given the massive variation among individuals, and the importance of individuals for communities, keystone individuals are likely to be common in systems as diverse as insect herbivores and human infectious diseases. Abstract Intraspecific variation is central to our understanding of evolution and ecology, but these fields generally consider either the mean trait value or its variance. Alternatively, the keystone individual concept from behavioral ecology posits that a single individual with an extreme phenotype can have disproportionate and irreplaceable effects on group dynamics. Here, I generalize this concept to include non-behavioral traits and broader ecological and evolutionary dynamics. I test for the effects of individuals with extreme phenotypes on the ecology and evolution of a gall-forming fly and its natural enemies that select for opposite gall sizes. Specifically I introduce a putatively keystone predator-attracting individual gall-maker, hypothesizing that the presence of such an individual should (i) increase gall-maker population-level mortality, (ii) cause consumer communities to be dominated by species that are most attracted to the keystone individual, (iii) increase selection for traits conferring defense against the most common consumer, and (iv) weaken patterns of stabilizing selection. I find support for both the ecological and evolutionary consequences of single individuals with extreme phenotypes, suggesting that they can be considered keystone individuals. I discuss the generality of the keystone individual concept, suggesting likely consequences for ecology and evolution. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695322 </i></p> <p><b>A single individual with extreme traits changes populations, communities, and evolution </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;">V</span>ariation among organisms&rsquo; characteristics (traits), whether among species, populations, or individuals, forms a central pillar of both ecology and evolution. Recently, work in community ecology has suggested that differences among individuals and populations can have enormous consequences for where species are found, their abundances, and how they interact with other species in the community. However, these studies have invariably considered differences in traits among populations (mean difference) or variation within a population (variance difference). As a result, we lack an ecological or evolutionary answer to the idiom &lsquo;can one person really make a difference?&rsquo;. Put otherwise, can the addition or removal of one specific individual from a population have large and irreplaceable effects on the ecology and evolution of the system?</p> <p>Here, Denon Start (University of Toronto, ON, Canada) extends the keystone individual concept from behavioral ecology to encompass ecology and evolutionary biology. Applied to ecology and evolution, he defines the keystone individual concept as the idea that certain individuals, usually with extreme (unusual) trait values, have important consequences, and that replacing an extreme individual with a &lsquo;normal&rsquo; individual would fundamentally change the ecological or evolutionary dynamics of the system.</p> <p>He then explores this concept at the Koffler Scientific Reserve in southern Ontario, using a gall-maker and its natural enemies. He shows that the presence of a single individual with an extreme predator-attracting phenotype increases mortality, changes the composition of predator communities, and increases selection for anti-predator traits in the surrounding gall-maker population. In short, the presence of a single individual with an extreme phenotype fundamentally changes the way the rest of the population interacts with other species, and the consequences of those interactions for selection. Given the massive variation among individuals, and the importance of individuals for communities, keystone individuals are likely to be common in systems as diverse as insect herbivores and human infectious diseases.</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>ntraspecific variation is central to our understanding of evolution and ecology, but these fields generally consider either the mean trait value or its variance. Alternatively, the keystone individual concept from behavioral ecology posits that a single individual with an extreme phenotype can have disproportionate and irreplaceable effects on group dynamics. Here, I generalize this concept to include non-behavioral traits and broader ecological and evolutionary dynamics. I test for the effects of individuals with extreme phenotypes on the ecology and evolution of a gall-forming fly and its natural enemies that select for opposite gall sizes. Specifically I introduce a putatively keystone predator-attracting individual gall-maker, hypothesizing that the presence of such an individual should (i) increase gall-maker population-level mortality, (ii) cause consumer communities to be dominated by species that are most attracted to the keystone individual, (iii) increase selection for traits conferring defense against the most common consumer, and (iv) weaken patterns of stabilizing selection. I find support for both the ecological and evolutionary consequences of single individuals with extreme phenotypes, suggesting that they can be considered keystone individuals. I discuss the generality of the keystone individual concept, suggesting likely consequences for ecology and evolution. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695322">Read&nbsp;the&nbsp;Article</a></p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Shared genes but not shared genetic variation: legume colonization by two belowground symbionts” http://amnat.org/an/newpapers/MarOssler.html The DOI will be http://dx.doi.org/10.1086/695829 Mutualisms are widely established interactions in nature. More often than not, hosts rely simultaneously on multiple symbionts—for example, humans and the microorganisms that make up the human microbiome, or economically important crops (such as soy beans) and their root symbionts. Hosts that rely on multiple symbionts often regulate them through shared genetic pathways. We can think of these genetic pathways as telephone party lines that help hosts regulate the density and exchange of resource interactions with multiple symbionts. However, it is still unclear if these shared pathways constrain the interactions between hosts and their symbionts, and what impacts these pathways could have on the evolution of populations.To address this question, Julia Ossler and Katy Heath examine the complex multiplayer mutualism among Chamaecrista fasciculata (partridge pea) and its two belowground symbionts (phosphorous acquiring arbuscular mycorrhizal fungi (AMF) and nitrogen fixing rhizobia). In a greenhouse experiment, they examine the response of 75 families of partridge pea to phosphorus fertilizer, specifically examining if changes in symbionts’ colonization on host roots are connected among families due to shared genetic pathways (“telephone party lines”). Understanding if shared genetic pathways generate limited multiplayer mutualism can help us understand how symbioses (co-)evolve in the context of complex natural communities. Despite the known existence of shared genetic pathways in the mutualism between partridge pea, AMF, and nitrogen fixing rhizobia, the researchers find that hosts retain the ability to interact and evolve independently with each symbiont, speaking to the potentially vast amount of genetic variation that may lie outside of shared genetic pathways, and the important role this plays in natural selection of mutualisms. Abstract Mutualisms between hosts and multiple symbionts can generate diffuse coevolution if genetic covariance exists between host traits governing multiple interactions. Rhizobia and arbuscular mycorrhizal fungi (AMF) both interact with legume hosts, providing complementary nutrients (nitrogen and phosphorous). Molecular approaches have revealed extensive pleiotropy in the plant genetic pathways required for colonization of both symbionts; however, a quantitative genetic approach is required to understand whether this pleiotropy shapes evolution in natural populations. In a greenhouse experiment with 75 families of Chamaecrista fasciculata grown in two phosphorous environments (fertilized and unfertilized), positive covariance between nodule number and plant aboveground biomass within and across environments indicates selection for increased colonization by rhizobia. Genetic variation for host restriction of AMF colonization in response to P suggests that this aspect of context-dependency can evolve in host populations, and that selection in this mutualism varies with P. Despite the existence of gene-level pleiotropy during rhizobium and AMF infection, we find no evidence for genetic covariance in symbiont colonization or its response to phosphorous – suggesting that genetic variation at other, non-pleiotropic loci govern variation in colonization and thus that these traits likely evolve independently in plant populations. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695829 </i></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>utualisms are widely established interactions in nature. More often than not, hosts rely simultaneously on multiple symbionts&mdash;for example, humans and the microorganisms that make up the human microbiome, or economically important crops (such as soy beans) and their root symbionts. Hosts that rely on multiple symbionts often regulate them through shared genetic pathways. We can think of these genetic pathways as telephone party lines that help hosts regulate the density and exchange of resource interactions with multiple symbionts. However, it is still unclear if these shared pathways constrain the interactions between hosts and their symbionts, and what impacts these pathways could have on the evolution of populations.</p><p>To address this question, Julia Ossler and Katy Heath examine the complex multiplayer mutualism among <i>Chamaecrista fasciculata</i> (partridge pea) and its two belowground symbionts (phosphorous acquiring arbuscular mycorrhizal fungi (AMF) and nitrogen fixing rhizobia). In a greenhouse experiment, they examine the response of 75 families of partridge pea to phosphorus fertilizer, specifically examining if changes in symbionts’ colonization on host roots are connected among families due to shared genetic pathways (“telephone party lines”). </p><p>Understanding if shared genetic pathways generate limited multiplayer mutualism can help us understand how symbioses (co-)evolve in the context of complex natural communities. Despite the known existence of shared genetic pathways in the mutualism between partridge pea, AMF, and nitrogen fixing rhizobia, the researchers find that hosts retain the ability to interact and evolve independently with each symbiont, speaking to the potentially vast amount of genetic variation that may lie outside of shared genetic pathways, and the important role this plays in natural selection of mutualisms. </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>utualisms between hosts and multiple symbionts can generate diffuse coevolution if genetic covariance exists between host traits governing multiple interactions. Rhizobia and arbuscular mycorrhizal fungi (AMF) both interact with legume hosts, providing complementary nutrients (nitrogen and phosphorous). Molecular approaches have revealed extensive pleiotropy in the plant genetic pathways required for colonization of both symbionts; however, a quantitative genetic approach is required to understand whether this pleiotropy shapes evolution in natural populations. In a greenhouse experiment with 75 families of <i>Chamaecrista fasciculata </i>grown in two phosphorous environments (fertilized and unfertilized), positive covariance between nodule number and plant aboveground biomass within and across environments indicates selection for increased colonization by rhizobia. Genetic variation for host restriction of AMF colonization in response to P suggests that this aspect of context-dependency can evolve in host populations, and that selection in this mutualism varies with P. Despite the existence of gene-level pleiotropy during rhizobium and AMF infection, we find no evidence for genetic covariance in symbiont colonization or its response to phosphorous – suggesting that genetic variation at other, non-pleiotropic loci govern variation in colonization and thus that these traits likely evolve independently in plant populations. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695829">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT “Coupling, reinforcement and speciation” http://amnat.org/an/newpapers/FebButlin-A.html The DOI will be http://dx.doi.org/10.1086/695136 Species are isolated by many barriers to gene flow working together. We ask how this coupling of barriers can evolveAbstract During the process of speciation, populations may diverge for traits, and at their underlying loci, that contribute barriers to gene flow. These barrier traits and barrier loci underlie individual barrier effects, by which we mean the contribution that a barrier locus or trait, or some combination of barrier loci or traits makes to overall isolation. The evolution of strong reproductive isolation typically requires the origin of multiple barrier effects. Critically, it also requires the coincidence of barrier effects: for example, two barrier effects, one due to assortative mating and the other due to hybrid inviability, create a stronger overall barrier to gene flow if they coincide than if they distinguish independent pairs of populations. Here, we define ‘coupling’ as any process that generates coincidence of barrier effects, resulting in a stronger overall barrier to gene flow. We argue that speciation research, both empirical and theoretical, needs to consider both the origin of barrier effects and the ways in which they are coupled. Coincidence of barrier effects can occur either as a by-product of selection on individual barrier effects or of population processes, or as an adaptive response to indirect selection. Adaptive coupling may be accompanied by further evolution that enhances individual barrier effects. Reinforcement, classically viewed as the evolution of pre-zygotic barriers to gene flow in response to costs of hybridization, is an example of this type of process. However, we argue for an extended view of reinforcement that includes coupling processes involving enhancement of any type of additional barrier effect as a result of an existing barrier. This view of coupling and reinforcement may help to guide development of both theoretical and empirical research on the process of speciation. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695136 </i></p> <p><b>Species are isolated by many barriers to gene flow working together. We ask how this coupling of barriers can evolve</b></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;">D</span>uring the process of speciation, populations may diverge for traits, and at their underlying loci, that contribute barriers to gene flow. These barrier traits and barrier loci underlie individual barrier effects, by which we mean the contribution that a barrier locus or trait, or some combination of barrier loci or traits makes to overall isolation. The evolution of strong reproductive isolation typically requires the origin of multiple barrier effects. Critically, it also requires the coincidence of barrier effects: for example, two barrier effects, one due to assortative mating and the other due to hybrid inviability, create a stronger overall barrier to gene flow if they coincide than if they distinguish independent pairs of populations. Here, we define &lsquo;coupling&rsquo; as any process that generates coincidence of barrier effects, resulting in a stronger overall barrier to gene flow. We argue that speciation research, both empirical and theoretical, needs to consider both the origin of barrier effects and the ways in which they are coupled. Coincidence of barrier effects can occur either as a by-product of selection on individual barrier effects or of population processes, or as an adaptive response to indirect selection. Adaptive coupling may be accompanied by further evolution that enhances individual barrier effects. Reinforcement, classically viewed as the evolution of pre-zygotic barriers to gene flow in response to costs of hybridization, is an example of this type of process. However, we argue for an extended view of reinforcement that includes coupling processes involving enhancement of <i>any type</i> of additional barrier effect as a result of an existing barrier. This view of coupling and reinforcement may help to guide development of both theoretical and empirical research on the process of speciation. <!-- <a href="http://dx.doi.org/10.1086/695136">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 Nov 2017 06:00:00 GMT Nominations for the 2018 Edward O. Wilson Naturalist Award, Due January 1 http://amnat.org/announcements/NomEOWilson.html The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career who has made significant contributions to the knowledge of a particular ecosystem or group of organisms. Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. The recipient need not be a member of the Society. The award will consist of an especially appropriate work of art and a prize of $2,000. The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;http://www.amnat.org/awards.html#Wilson Nominations will be held over for two years. The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 1, 2018, to David Skelly. david.skelly@yale.edu Please indicate "E. O. Wilson Award" in the subject line.&nbsp; <p>The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career who has made significant contributions to the knowledge of a particular ecosystem or group of organisms. Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. <em>The recipient need not be a member of the Society</em>. The award will consist of an especially appropriate work of art and a prize of $2,000.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;<a href="http://www.amnat.org/awards.html#Wilson">http://www.amnat.org/awards.html#Wilson</a></p> <p>Nominations will be held over for two years.</p> <p>The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 1, 2018, to David Skelly. <a href="mailto:david.skelly@yale.edu">david.skelly@yale.edu</a> Please indicate &quot;E. O. Wilson Award&quot; in the subject line.&nbsp;</p> Mon, 13 Nov 2017 06:00:00 GMT Hurricane Relief http://amnat.org/announcements/Relief.html The American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean. We have allocated $8,000 to this effort from our existing funds, to be distributed as grants of up to $2000. We would like to distribute more funds using your donations. If you would like to donate to this effort, please visit the following link for “ASN Funds for Hurricane Recovery.” https://subfill.uchicago.edu/JournalPubs/Donation.aspx?webpub=ANXThe American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean, up to $2000. If you would like to apply, please send an application with the following information: 1.&nbsp;&nbsp; &nbsp;Your name, E-mail, Professional mailing address, Preferred mailing address, if different 2.&nbsp;&nbsp; &nbsp;Your Institution, Department, and Position 3.&nbsp;&nbsp; &nbsp;Are you and ASN member? Is your mentor and ASN member? 4.&nbsp;&nbsp; &nbsp;Brief description of the loss experienced because of the hurricanes and how an award from ASN would be used Please send application materials to Manuel Leal, at: lealm@missouri.edu <p>The American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean. We have allocated $8,000 to this effort from our existing funds, to be distributed as grants of up to $2000. We would like to distribute more funds using your donations. If you would like to donate to this effort, please visit the following link for &ldquo;ASN Funds for Hurricane Recovery.&rdquo;<br /> <a href="https://subfill.uchicago.edu/JournalPubs/Donation.aspx?webpub=ANX">https://subfill.uchicago.edu/JournalPubs/Donation.aspx?webpub=ANX</a></p><p>The American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean, up to $2000. If you would like to apply, please send an application with the following information:<br /> 1.&nbsp;&nbsp; &nbsp;Your name, E-mail, Professional mailing address, Preferred mailing address, if different<br /> 2.&nbsp;&nbsp; &nbsp;Your Institution, Department, and Position<br /> 3.&nbsp;&nbsp; &nbsp;Are you and ASN member? Is your mentor and ASN member?<br /> 4.&nbsp;&nbsp; &nbsp;Brief description of the loss experienced because of the hurricanes and how an award from ASN would be used<br /> Please send application materials to Manuel Leal, at: <a href="mailto:lealm@missouri.edu">lealm@missouri.edu</a></p> Mon, 13 Nov 2017 06:00:00 GMT Applications for the 2018 ASN Student Research Awards, due January 31 http://amnat.org/announcements/StudentResearchAward.html The ASN Student Research Awards: The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must be a member of the ASN (membership is international), must hold a bachelor’s degree or equivalent, must have passed to candidacy in a Ph.D. program or equivalent, and must be at least one year from completing the Ph.D. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. A total of ten proposals will receive awards. Proposals will be judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission. Applications include four elements: 1) A two-page proposal describing the research project for which support is requested; 2) A budget with justification (one page); 3) a short curriculum vitae (two pages); 4) a statement from the Ph.D. supervisor that verifies that the applicant meets the eligibility requirements, and confirms the supervisor’s support for the proposed project (one page). Detailed Instructions: The two-page proposal should describe a specific research project for which support is requested.&nbsp; While some background and context is appropriate, the proposal should not be a general overview of the applicant’s complete dissertation.&nbsp; The proposal should have a title at the top of the first page.&nbsp; The proposal should be single-spaced, have 1-inch (2.5cm) margins all around, and be written in an 11- or 12-point standard font on 8.5 x 11 inch pages.&nbsp; A list of references should follow, but is not included in the 2-page limit. The budget and budget justification should clearly support the specific proposed project.&nbsp; If total costs of the project exceed $2000, some indication of how the applicant intends to find support for remaining costs should be given. The CV should meet the same formatting requirements as the project description. All materials should be compiled into one PDF.&nbsp; The .pdf filename should be in the format Lastname_Firstname_SRA (example:&nbsp; Wright_Sewall_RSA.pdf). Send your application via e-mail to Dr. Jeff Dudycha at AmNatSRA@gmail.com with “ASN Student Research Award” in the subject line. Deadline for submission of all materials is January 31, 2018. Judging: Applications will be reviewed by a committee of six persons: three faculty-level researchers and three graduate students. Senior-level appointments are made by the President-Elect. Members each serve for three years; the longest-serving faculty-level committee member serves as chair in her/his final year on the committee. Graduate student appointments are made from the Graduate Council, in consultation with the President-Elect. <p><strong>The ASN Student Research Awards:</strong></p> <p>The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must be a member of the ASN (membership is international), must hold a bachelor&rsquo;s degree or equivalent, must have passed to candidacy in a Ph.D. program or equivalent, and must be at least one year from completing the Ph.D. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. A total of ten proposals will receive awards. Proposals will be judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission.</p> <p>Applications include four elements: 1) A two-page proposal describing the research project for which support is requested; 2) A budget with justification (one page); 3) a short curriculum vitae (two pages); 4) a statement from the Ph.D. supervisor that verifies that the applicant meets the eligibility requirements, and confirms the supervisor&rsquo;s support for the proposed project (one page).</p> <p><strong>Detailed Instructions:</strong></p> <ol> <li>The two-page proposal should describe a specific research project for which support is requested.&nbsp; While some background and context is appropriate, the proposal should not be a general overview of the applicant&rsquo;s complete dissertation.&nbsp; The proposal should have a title at the top of the first page.&nbsp; The proposal should be single-spaced, have 1-inch (2.5cm) margins all around, and be written in an 11- or 12-point standard font on 8.5 x 11 inch pages.&nbsp; A list of references should follow, but is not included in the 2-page limit.</li> <li>The budget and budget justification should clearly support the specific proposed project.&nbsp; If total costs of the project exceed $2000, some indication of how the applicant intends to find support for remaining costs should be given.</li> <li>The CV should meet the same formatting requirements as the project description.</li> <li><strong>All materials should be compiled into one PDF.&nbsp; The .pdf filename should be in the format Lastname_Firstname_SRA (example:&nbsp; Wright_Sewall_RSA.pdf).</strong></li> <li>Send your application via e-mail to Dr. Jeff Dudycha at <a href="http://AmNatSRA@gmail.com">AmNatSRA@gmail.com</a> with &ldquo;ASN Student Research Award&rdquo; in the subject line.</li> <li>Deadline for submission of all materials is January 31, 2018.</li> </ol> <p><strong>Judging:</strong></p> <p>Applications will be reviewed by a committee of six persons: three faculty-level researchers and three graduate students. Senior-level appointments are made by the President-Elect. Members each serve for three years; the longest-serving faculty-level committee member serves as chair in her/his final year on the committee. Graduate student appointments are made from the Graduate Council, in consultation with the President-Elect.</p> Mon, 13 Nov 2017 06:00:00 GMT Nominations for the 2018 Sewall Wright Award, Due January 1 http://amnat.org/announcements/NomWright.html The American Society of Naturalists invites applications for the 2018 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator, who is making fundamental contributions to the Society’s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2018 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society. The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all area’s of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years. The names of former recipients can be found here: http://www.amnat.org/awards.html#Wright For the 2018 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by January 1, 2018, via e-mail to Andr&eacute; M. de Roos (A.M.deRoos@uva.nl). Please indicate “Sewall Wright Award” in the subject line and let the filename of the nomination letter indicate the name of the nominee. <p>The American Society of Naturalists invites applications for the 2018 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator, who is making fundamental contributions to the Society&rsquo;s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2018 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all area&rsquo;s of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years.</p> <p>The names of former recipients can be found here:<br /> <a href="http://www.amnat.org/awards.html#Wright">http://www.amnat.org/awards.html#Wright</a></p> <p>For the 2018 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by January 1, 2018, via e-mail to Andr&eacute; M. de Roos (<a href="mailto:A.M.deRoos@uva.nl">A.M.deRoos@uva.nl</a>). Please indicate &ldquo;Sewall Wright Award&rdquo; in the subject line and let the filename of the nomination letter indicate the name of the nominee.</p> Thu, 09 Nov 2017 06:00:00 GMT “Do sperm really compete and do eggs ever have a choice? Adult distribution and gamete mixing influence sexual selection, sexual conflict, and the evolution of gamete recognition proteins in the sea” http://amnat.org/an/newpapers/JanLevitan.html Sperm compete and eggs choose in externally fertilizing species There is a long history of studies that examine male competition and female choice, but in many cases females mate with multiple males and it is not clear whether the sperm from one male directly competes with the sperm from another male in the race to fertilize an individual egg. When sperm arrive simultaneously to an egg, it provides an opportunity for eggs to choose sperm from competing males. Don Levitan examines this question using sea urchins by conducting underwater experiments off the Pacific coast of Canada. He finds that when sea urchin density is high, sperm from multiple males can mix to the degree that sperm competition and egg choice are likely and that the winner of this competition is predicted by the sperm proteins that interact with the egg surface. When sea urchin density is lower, eggs are surrounded by the sperm from single males and the male that wins is determined by which sperm arrives first and not by protein interactions. These results shed light on patterns of sperm competition and egg choice in the sea and more broadly how ecological conditions can influence the evolution of compatibility between sperm and eggs. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Sperm compete and eggs choose in externally fertilizing species </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>here is a long history of studies that examine male competition and female choice, but in many cases females mate with multiple males and it is not clear whether the sperm from one male directly competes with the sperm from another male in the race to fertilize an individual egg. When sperm arrive simultaneously to an egg, it provides an opportunity for eggs to choose sperm from competing males. Don Levitan examines this question using sea urchins by conducting underwater experiments off the Pacific coast of Canada. He finds that when sea urchin density is high, sperm from multiple males can mix to the degree that sperm competition and egg choice are likely and that the winner of this competition is predicted by the sperm proteins that interact with the egg surface. When sea urchin density is lower, eggs are surrounded by the sperm from single males and the male that wins is determined by which sperm arrives first and not by protein interactions. These results shed light on patterns of sperm competition and egg choice in the sea and more broadly how ecological conditions can influence the evolution of compatibility between sperm and eggs. <a href="http://dx.doi.org/10.1086/694780">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 06 Nov 2017 06:00:00 GMT “Kinship and incest avoidance drive patterns of reproductive skew in cooperatively breeding birds” http://amnat.org/an/newpapers/DecRiehl.html Why is reproduction unequal among members of social animal groups? New research suggests that incest avoidance is key Cooperatively breeding animals vary in how reproduction is divided among group members. In some species, several individuals all reproduce and share care of the mixed brood; in others, a dominant individual or pair monopolizes reproduction and is assisted by non-breeding “helpers.” Although the degree of reproductive sharing, or “skew,” has been a popular subject of theoretical models, researchers still disagree about the reasons for this variation. In the first large-scale analysis across species, a new study in The&nbsp;American Naturalist shows that patterns of genetic relatedness among members of cooperative groups are the best predictors of whether reproduction is shared. Using data from over 80 species of cooperatively breeding birds, Christina Riehl of Princeton University has found that reproduction tends to be shared when group members are unrelated, whereas one pair tends to dominate in family groups. This general pattern—high skew in families and low skew with non-relatives—has been proposed before, and is supported by prominent theoretical models. But why? What prevents relatives from breeding together and producing offspring in the same nest? Two different mechanisms have been proposed. First, dominant group members might actively prevent related subordinates from reproducing; for example, a dominant female might prevent her younger relatives from laying eggs in her nest. Alternatively, given that inbreeding can have fitness costs, helpers might be less likely to reproduce if their only potential mates are relatives. In support of the latter hypothesis, Riehl finds that incest avoidance is the most likely reason that relatives don’t breed together. Helpers in cooperative groups were more likely to breed if they were unrelated to opposite-sex group members, whereas relatedness to same-sex group members had no effect. These results provide the first wide-scale evidence that incest avoidance constrains reproduction in cooperative groups, and they suggest new lines of inquiry for theoretical models. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Why is reproduction unequal among members of social animal groups? New research suggests that incest avoidance is key </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>ooperatively breeding animals vary in how reproduction is divided among group members. In some species, several individuals all reproduce and share care of the mixed brood; in others, a dominant individual or pair monopolizes reproduction and is assisted by non-breeding “helpers.” Although the degree of reproductive sharing, or “skew,” has been a popular subject of theoretical models, researchers still disagree about the reasons for this variation. In the first large-scale analysis across species, a new study in <i>The&nbsp;American Naturalist</i> shows that patterns of genetic relatedness among members of cooperative groups are the best predictors of whether reproduction is shared. Using data from over 80 species of cooperatively breeding birds, Christina Riehl of Princeton University has found that reproduction tends to be shared when group members are unrelated, whereas one pair tends to dominate in family groups. </p><p>This general pattern—high skew in families and low skew with non-relatives—has been proposed before, and is supported by prominent theoretical models. But why? What prevents relatives from breeding together and producing offspring in the same nest? Two different mechanisms have been proposed. First, dominant group members might actively prevent related subordinates from reproducing; for example, a dominant female might prevent her younger relatives from laying eggs in her nest. Alternatively, given that inbreeding can have fitness costs, helpers might be less likely to reproduce if their only potential mates are relatives. In support of the latter hypothesis, Riehl finds that incest avoidance is the most likely reason that relatives don’t breed together. Helpers in cooperative groups were more likely to breed if they were unrelated to opposite-sex group members, whereas relatedness to same-sex group members had no effect. These results provide the first wide-scale evidence that incest avoidance constrains reproduction in cooperative groups, and they suggest new lines of inquiry for theoretical models. <a href="http://dx.doi.org/10.1086/694411">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 03 Nov 2017 05:00:00 GMT “Loss of color pigmentation is maintained at high frequency in a monkey flower population” http://amnat.org/an/newpapers/JanTwyford.html Loss of anthocyanin pigmentation has risen to an unexpectedly high frequency in a population of Mimulus Almost all land plants make red pigmentation (anthocyanin) in their vegetative tissues or flowers at some point during their lives. It is thought that this pigment protects plants against UV damage, drought, and herbivory, and is also involved in attracting pollinators. A recent discovery finds a population of common monkey flowers (Mimulus guttatus) where a single recessive allele causes complete loss of anthocyanin, and has spread through the population. Alex Twyford and Jannice Friedman first noticed this unique trait in plants grown in the greenhouse, and then returned to the population in Sequoia National Forest to investigate more closely. The team discovered that the genetic variant underlying complete loss of anthocyanin pigmentation has risen to an unexpectedly high frequency in this population. They also found a gene that is likely to be involved, the MYB5 transcription factor, as the unpigmented morphs showed decreased expression in both leaves and floral buds. They then designed 3 sets of experiments to look for fitness differences between the plants that make anthocyanin and those that don’t. They could not find any difference in survival, flowering or seed set, although the unpigmented plants flowered later and grew more clonally. Although they can’t rule out a cryptic selection pressure in the wild, their findings challenge our assumption that the production of anthocyanin is beneficial for plants. The visible color polymorphism also provides an opportunity to examine the dynamics between selection and genetic drift in a well-studied plant species. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Loss of anthocyanin pigmentation has risen to an unexpectedly high frequency in a population of <i>Mimulus</i> </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>lmost all land plants make red pigmentation (anthocyanin) in their vegetative tissues or flowers at some point during their lives. It is thought that this pigment protects plants against UV damage, drought, and herbivory, and is also involved in attracting pollinators. A recent discovery finds a population of common monkey flowers (<i>Mimulus guttatus</i>) where a single recessive allele causes complete loss of anthocyanin, and has spread through the population. Alex Twyford and Jannice Friedman first noticed this unique trait in plants grown in the greenhouse, and then returned to the population in Sequoia National Forest to investigate more closely. The team discovered that the genetic variant underlying complete loss of anthocyanin pigmentation has risen to an unexpectedly high frequency in this population. They also found a gene that is likely to be involved, the MYB5 transcription factor, as the unpigmented morphs showed decreased expression in both leaves and floral buds. They then designed 3 sets of experiments to look for fitness differences between the plants that make anthocyanin and those that don’t. They could not find any difference in survival, flowering or seed set, although the unpigmented plants flowered later and grew more clonally. Although they can’t rule out a cryptic selection pressure in the wild, their findings challenge our assumption that the production of anthocyanin is beneficial for plants. The visible color polymorphism also provides an opportunity to examine the dynamics between selection and genetic drift in a well-studied plant species. <a href="http://dx.doi.org/10.1086/694853">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 03 Nov 2017 05:00:00 GMT “Temporal variation in predation risk may explain daily rhythms of foraging behavior in an orb-weaving spider” http://amnat.org/an/newpapers/JanWatts.html Nocturnal foraging may be an adaptive response to predation risk in an orb-weaving spiderUsing a combination of mathematical modeling and around-the-clock field observations, researchers from the University of Nebraska-Lincoln and East Tennessee State University lend new insights to a potential ecological explanation for the evolution of daily rhythms of behavior. For many organisms, the earth’s daily rotation corresponds to some of the most predictable and profound changes in environmental conditions. Unsurprisingly, organisms from across the tree of life express changes in their characteristics at various scales over the daily cycle, ranging from changes in gene expression to rhythms of foraging and sexual behavior. Despite the prevalence of these biological rhythms and extensive research on the mechanisms that produce them, evidence for specific ecological processes that might favor their evolution remains sparse. Many organisms likely experience daily changes in predation risk that could favor the evolution of daily rhythms. Colton Watts and colleagues created a model of foraging decisions over the course of the day to investigate whether changes in predation risk can explain observed daily rhythms. As a case study, the researchers used data on daily changes in predator and prey abundance experienced by a common orb-weaving spider, Cyclosa turbinata. The researchers found that well-fed individuals should benefit from decreasing their foraging activity during the day, when both their wasp predators and flying insect prey are most abundant. By deploying surveillance cameras to observe C.&nbsp;turbinata spiders around-the-clock under natural conditions, Watts and colleagues found that, as predicted, individuals attacked prey less often during the daytime. In addition to demonstrating a potential role of predation risk in the evolution of daily rhythms, the model generates new predictions that will guide experiments assessing the importance of predation risk for the daily routines of other organisms. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Nocturnal foraging may be an adaptive response to predation risk in an orb-weaving spider</b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>sing a combination of mathematical modeling and around-the-clock field observations, researchers from the University of Nebraska-Lincoln and East Tennessee State University lend new insights to a potential ecological explanation for the evolution of daily rhythms of behavior. </p><p>For many organisms, the earth’s daily rotation corresponds to some of the most predictable and profound changes in environmental conditions. Unsurprisingly, organisms from across the tree of life express changes in their characteristics at various scales over the daily cycle, ranging from changes in gene expression to rhythms of foraging and sexual behavior. Despite the prevalence of these biological rhythms and extensive research on the mechanisms that produce them, evidence for specific ecological processes that might favor their evolution remains sparse. </p><p>Many organisms likely experience daily changes in predation risk that could favor the evolution of daily rhythms. Colton Watts and colleagues created a model of foraging decisions over the course of the day to investigate whether changes in predation risk can explain observed daily rhythms. As a case study, the researchers used data on daily changes in predator and prey abundance experienced by a common orb-weaving spider, <i>Cyclosa turbinata</i>. The researchers found that well-fed individuals should benefit from decreasing their foraging activity during the day, when both their wasp predators and flying insect prey are most abundant. By deploying surveillance cameras to observe <i>C.&nbsp;turbinata</i> spiders around-the-clock under natural conditions, Watts and colleagues found that, as predicted, individuals attacked prey less often during the daytime. In addition to demonstrating a potential role of predation risk in the evolution of daily rhythms, the model generates new predictions that will guide experiments assessing the importance of predation risk for the daily routines of other organisms. <a href="http://dx.doi.org/10.1086/694775">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 03 Nov 2017 05:00:00 GMT “Theoretical approaches in evolutionary ecology: environmental feedback as a unifying perspective” http://amnat.org/an/newpapers/JanLion.html Time scales and environmental feedback in the different theoretical approaches to evolutionary ecology Among biological sciences, evolutionary biology and ecology have a unique relationship with mathematics. In both fields, mathematical theory has been a key ingredient of conceptual innovation and theoretical progress. The use of mathematical models is necessary because both evolutionary biologists and ecologists seek to understand complex biological systems characterized by multiple time scales and levels of organization. In the last 50 years, a rich theoretical literature has been devoted to understanding the interplay between ecological processes and evolution. Unfortunately, a large part of this literature hinges on sophisticated mathematics that are beyond the training of many biologists. Furthermore, theoretical evolutionary ecology tends to be divided among different schools of thought with different toolboxes, such as quantitative genetics or evolutionary game theory. The aim of this synthesis by Sébastien Lion of the Centre National pour la Recherche Scientifique in Montpellier, France, is to highlight the connections between these different approaches and to clarify the current state of theory in evolutionary ecology. The author discusses the interplay between the feedback of the environment and the time scales of ecological and evolutionary processes. This notion of environmental feedback can be traced all the way back to Darwin and is key to an intuitive ecological approach to evolution. In this synthesis, the author uses this unifying perspective to revisit various key results of evolutionary theory, such as the Price equation, Fisher’s fundamental theorem of natural selection, or the notion of evolutionarily stable strategy. This is a call for pluralism and integration in a field that has often been divided by acute debates between theoretical schools. Such debates, which often result from minor technical quibbles blown out of proportion, have occasionally reached an unprepared general public, with damaging consequences for the reputation of evolutionary biology. This synthesis chooses to celebrate the solid unity of the mathematical theory of evolution. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Time scales and environmental feedback in the different theoretical approaches to evolutionary ecology </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>mong biological sciences, evolutionary biology and ecology have a unique relationship with mathematics. In both fields, mathematical theory has been a key ingredient of conceptual innovation and theoretical progress. The use of mathematical models is necessary because both evolutionary biologists and ecologists seek to understand complex biological systems characterized by multiple time scales and levels of organization. In the last 50 years, a rich theoretical literature has been devoted to understanding the interplay between ecological processes and evolution. Unfortunately, a large part of this literature hinges on sophisticated mathematics that are beyond the training of many biologists. Furthermore, theoretical evolutionary ecology tends to be divided among different schools of thought with different toolboxes, such as quantitative genetics or evolutionary game theory. </p> <p>The aim of this synthesis by Sébastien Lion of the Centre National pour la Recherche Scientifique in Montpellier, France, is to highlight the connections between these different approaches and to clarify the current state of theory in evolutionary ecology. The author discusses the interplay between the feedback of the environment and the time scales of ecological and evolutionary processes. This notion of environmental feedback can be traced all the way back to Darwin and is key to an intuitive ecological approach to evolution. In this synthesis, the author uses this unifying perspective to revisit various key results of evolutionary theory, such as the Price equation, Fisher’s fundamental theorem of natural selection, or the notion of evolutionarily stable strategy. This is a call for pluralism and integration in a field that has often been divided by acute debates between theoretical schools. Such debates, which often result from minor technical quibbles blown out of proportion, have occasionally reached an unprepared general public, with damaging consequences for the reputation of evolutionary biology. This synthesis chooses to celebrate the solid unity of the mathematical theory of evolution. <a href="http://dx.doi.org/10.1086/694865">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 03 Nov 2017 05:00:00 GMT “The Price equation, gradient dynamics, and continuous trait game theory” http://amnat.org/an/newpapers/JanLehtonen.html The Price equation can be used to derive foundational results in game theory and gradient dynamics The variety of mathematical approaches to modeling natural selection can be bewildering. Although Darwin himself did not provide a mathematical framework for his ideas, this has long since changed, with methods from probability theory to calculus finding a home in evolutionary theory. Luckily, an equation derived by George Price in the 1970s has the level of generality required to unify many seemingly different mathematical approaches. In a recent article in The&nbsp;American Naturalist, David Queller showed how the Price equation unifies a number of important mathematical results in evolutionary theory. In a new article, Jussi Lehtonen of the University of New South Wales in Sydney, Australia, extends Queller’s analysis to derive several fundamental results in the analysis of the evolution of continuous traits using calculus. Combining the Price equation with Taylor polynomials illuminates similarities and differences between approaches, and allows a simple, unified view of game-theoretical and dynamic concepts. Doing so also connects the power of calculus to evolutionary modeling. The same basic approach of applying the Price equation to Taylor polynomials can be used to derive dynamic gradient models, the criterion for evolutionary stability, as well as the direct fitness approach to kin selection. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>The Price equation can be used to derive foundational results in game theory and gradient dynamics </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he variety of mathematical approaches to modeling natural selection can be bewildering. Although Darwin himself did not provide a mathematical framework for his ideas, this has long since changed, with methods from probability theory to calculus finding a home in evolutionary theory. Luckily, an equation derived by George Price in the 1970s has the level of generality required to unify many seemingly different mathematical approaches. In a recent article in <i>The&nbsp;American Naturalist</i>, David Queller showed how the Price equation unifies a number of important mathematical results in evolutionary theory. In a new article, Jussi Lehtonen of the University of New South Wales in Sydney, Australia, extends Queller’s analysis to derive several fundamental results in the analysis of the evolution of continuous traits using calculus. Combining the Price equation with Taylor polynomials illuminates similarities and differences between approaches, and allows a simple, unified view of game-theoretical and dynamic concepts. Doing so also connects the power of calculus to evolutionary modeling. The same basic approach of applying the Price equation to Taylor polynomials can be used to derive dynamic gradient models, the criterion for evolutionary stability, as well as the direct fitness approach to kin selection. <a href="http://dx.doi.org/10.1086/694891">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 03 Nov 2017 05:00:00 GMT “Local regulation of trail networks of the arboreal turtle ant, Cephalotes goniodontus” http://amnat.org/an/newpapers/DecGordon.html Turtle ants make resilient trail networks in the canopy of the tropical forest Turtle ants in the tangled canopy of the tropical dry forest in western Mexico make a network of trails that builds on the network of vegetation. The nodes of the network are junctions from one branch, stem or vine to another, and the edges are the stems or branches that the ants move along. The ants lay pheromone as they go. This study asks how a colony, operating without central control, is able to use simple local cues to maintain, build and repair its highway system. The trail network links nests and food sources, so ants must keep circulating around it to keep the colony together. But ants find baits away from the trail, showing that some ants occasionally choose a new path through a junction. This slight tendency to make an error allows the ants to repair trails as well as to find new food sources. Often branches are broken by the wind or animals passing through. In experiments in which stems along the path were cut, the ants quickly found new paths, using “breadth-first search” that starts from the nodes nearest the break. The turtle ants’ resilient algorithm for maintenance and repair may be useful for engineered networks. The algorithm does not produce the shortest possible path, but instead the path that minimizes the number of nodes at which ants could take the wrong turn and get lost. It keeps the ants on coherent trails, while providing a way to repair ruptures quickly and explore for new resources. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Turtle ants make resilient trail networks in the canopy of the tropical forest </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>urtle ants in the tangled canopy of the tropical dry forest in western Mexico make a network of trails that builds on the network of vegetation. The nodes of the network are junctions from one branch, stem or vine to another, and the edges are the stems or branches that the ants move along. The ants lay pheromone as they go. This study asks how a colony, operating without central control, is able to use simple local cues to maintain, build and repair its highway system. </p><p>The trail network links nests and food sources, so ants must keep circulating around it to keep the colony together. But ants find baits away from the trail, showing that some ants occasionally choose a new path through a junction. This slight tendency to make an error allows the ants to repair trails as well as to find new food sources. Often branches are broken by the wind or animals passing through. In experiments in which stems along the path were cut, the ants quickly found new paths, using “breadth-first search” that starts from the nodes nearest the break. </p><p>The turtle ants’ resilient algorithm for maintenance and repair may be useful for engineered networks. The algorithm does not produce the shortest possible path, but instead the path that minimizes the number of nodes at which ants could take the wrong turn and get lost. It keeps the ants on coherent trails, while providing a way to repair ruptures quickly and explore for new resources. <a href="http://dx.doi.org/10.1086/693418">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 24 Oct 2017 05:00:00 GMT “Drivers of diversification in individual life courses” http://amnat.org/an/newpapers/DecHernPach.html Variability in life courses does not depend on ecological mechanisms underlying population structural composition The evolution of populations is shaped by demographic differences among individuals in their life courses. Yet thorough examination of the mechanisms behind individual differences remains undone because current population level analyses center on mean factors that average over such mechanisms. In this study, the authors use a novel approach to investigate principal drivers of individual differences in Cayo Santiago rhesus macaques. Using 40 years of demographic data on over 3,000 rhesus females, researchers study the relationship between population density and the rate at which the diversity of female life courses diversify with age. The authors show that density regulates the annual distribution of reproductive success in the population, but the rate of diversification is independent of density. For example, they find that as population density increases, the proportion of successful breeders decreases. However, such change in density does not affect the life course of these females. This suggests that an increase in density neither drives individuals to a certain optimal life course, nor forces individuals to explore new niches by diversifying life courses. This study may be the first to demonstrate that year-to-year variation in the rate of diversification of life courses is independent of the well-known ecological mechanisms underlying structural composition in a population, such as density-dependence. The study also illustrates how the measure of the rate of diversification provides a more integrated estimate of variability compared to the population structural composition, giving us new insights about the underlying drivers of individual differences within populations and potential evolutionary mechanisms. The authors, Raisa Hernández-Pacheco and Ulrich K. Steiner, are at the University of Puerto Rico and the University of Southern Denmark, respectively. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Variability in life courses does not depend on ecological mechanisms underlying population structural composition </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 evolution of populations is shaped by demographic differences among individuals in their life courses. Yet thorough examination of the mechanisms behind individual differences remains undone because current population level analyses center on mean factors that average over such mechanisms. </p><p>In this study, the authors use a novel approach to investigate principal drivers of individual differences in Cayo Santiago rhesus macaques. Using 40 years of demographic data on over 3,000 rhesus females, researchers study the relationship between population density and the rate at which the diversity of female life courses diversify with age. The authors show that density regulates the annual distribution of reproductive success in the population, but the rate of diversification is independent of density. For example, they find that as population density increases, the proportion of successful breeders decreases. However, such change in density does not affect the life course of these females. This suggests that an increase in density neither drives individuals to a certain optimal life course, nor forces individuals to explore new niches by diversifying life courses. </p><p>This study may be the first to demonstrate that year-to-year variation in the rate of diversification of life courses is independent of the well-known ecological mechanisms underlying structural composition in a population, such as density-dependence. The study also illustrates how the measure of the rate of diversification provides a more integrated estimate of variability compared to the population structural composition, giving us new insights about the underlying drivers of individual differences within populations and potential evolutionary mechanisms. </p><p>The authors, Raisa Hernández-Pacheco and Ulrich K. Steiner, are at the University of Puerto Rico and the University of Southern Denmark, respectively. <a href="http://dx.doi.org/10.1086/694317">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 24 Oct 2017 05:00:00 GMT “Will invertebrates require increasingly carbon-rich food in a warming world?” http://amnat.org/an/newpapers/DecAnderson.html Elevated temperature increases the energetic requirements (respiration) of invertebrates such as water fleas and grasshoppers. These animals should therefore require increasingly energy- (carbon-) rich food in a warming world. However, researchers challenge this idea using a mathematical model in a new study appearing in The&nbsp;American Naturalist. The new research shows that, because warming increases not only respiration but also the rate at which animals can collect food, optimal diet (the relative requirement for carbon versus nutrient elements) in order to prosper and grow may (contrary to expectations) change little, if at all, at higher temperatures. The carbon content of plant matter is expected to increase as the world warms, leading to a surplus of available energy. The study indicates that, during grazing, invertebrates will release some of this surplus as faeces or carbon dioxide, thereby changing the way in which these organisms interact with the global carbon cycle. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>levated temperature increases the energetic requirements (respiration) of invertebrates such as water fleas and grasshoppers. These animals should therefore require increasingly energy- (carbon-) rich food in a warming world. However, researchers challenge this idea using a mathematical model in a new study appearing in <i>The&nbsp;American Naturalist</i>. The new research shows that, because warming increases not only respiration but also the rate at which animals can collect food, optimal diet (the relative requirement for carbon versus nutrient elements) in order to prosper and grow may (contrary to expectations) change little, if at all, at higher temperatures. The carbon content of plant matter is expected to increase as the world warms, leading to a surplus of available energy. The study indicates that, during grazing, invertebrates will release some of this surplus as faeces or carbon dioxide, thereby changing the way in which these organisms interact with the global carbon cycle. <a href="http://dx.doi.org/10.1086/694122">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 24 Oct 2017 05:00:00 GMT “Rapid diversification and time explain amphibian species richness at different scales in the Tropical Andes, Earth’s most biodiverse hotspot” http://amnat.org/an/newpapers/DecHutter-A.html Rapid diversification and time explain amphibian richness at different scales in the Tropical Andes Abstract The Tropical Andes make up Earth’s most species-rich biodiversity hotspot for both animals and plants. Nevertheless, the ecological and evolutionary processes underlying this extraordinary richness remain uncertain. Here, we examine the processes that generate high richness in the Tropical Andes relative to other regions in South America, and across different elevations within the Andes, using frogs as a model system. We combine distributional data, a newly generated time-calibrated phylogeny for 2318 frog species, and phylogenetic comparative methods to test the relative importance of diversification rates and colonization times for explaining Andean diversity at different scales. At larger scales (among regions and families), we find that faster diversification rates in Andean clades most likely explain high Andean richness. In contrast, at smaller temporal and spatial scales (within family-level clades, within the Andes), diversification rates rarely explain richness patterns. Instead, we show that colonization times are important for shaping elevational richness patterns within the Andes, with more species found in habitats colonized earlier. We suggest that these scale-dependent patterns might apply to many other richness gradients. Recognition of this scale-dependence may help to reconcile conflicting results among studies of richness patterns across habitats, regions, and organisms. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Rapid diversification and time explain amphibian richness at different scales in the Tropical Andes </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 Tropical Andes make up Earth’s most species-rich biodiversity hotspot for both animals and plants. Nevertheless, the ecological and evolutionary processes underlying this extraordinary richness remain uncertain. Here, we examine the processes that generate high richness in the Tropical Andes relative to other regions in South America, and across different elevations within the Andes, using frogs as a model system. We combine distributional data, a newly generated time-calibrated phylogeny for 2318 frog species, and phylogenetic comparative methods to test the relative importance of diversification rates and colonization times for explaining Andean diversity at different scales. At larger scales (among regions and families), we find that faster diversification rates in Andean clades most likely explain high Andean richness. In contrast, at smaller temporal and spatial scales (within family-level clades, within the Andes), diversification rates rarely explain richness patterns. Instead, we show that colonization times are important for shaping elevational richness patterns within the Andes, with more species found in habitats colonized earlier. We suggest that these scale-dependent patterns might apply to many other richness gradients. Recognition of this scale-dependence may help to reconcile conflicting results among studies of richness patterns across habitats, regions, and organisms. <a href="http://dx.doi.org/10.1086/694319">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 24 Oct 2017 05:00:00 GMT “Thermoregulatory behavior simultaneously promotes and forestalls evolution in a tropical lizard” http://amnat.org/an/newpapers/JanMunoz.html Behavioral drive meets behavioral inertia: One behavior has different evolutionary effects on physiology and morphology Evolution can be both stimulated and halted by an animal’s behavior, according to a groundbreaking study led by a Virginia Tech researcher. It just depends which trait you’re talking about. The study, appearing in The&nbsp;American Naturalist, shows that behavior can be both a brake and a motor for evolution in a manner where slowing evolution in one trait actually requires accelerating evolution in another, according to Martha Muñoz, a new assistant professor at Virginia Tech, and Jonathan B. Losos of Harvard. Understanding this delicate stop-and-go dance can help scientists predict how animals will adapt to global change such as climate change and habitat degradation. In the case of the anole lizard of the Dominican Republic, thermoregulation—or the ability to control one’s own body temperature—is crucial to survival. Although it is located in the tropics, the Dominican Republic has lots of mountainous habitat and high elevations that challenge animals like lizards, which cannot regulate their temperature internally, the way that birds and mammals (including people) do. When the lizards migrated from warm, low elevations to cool, high elevations, body temperature regulation required the lizard to take up a new microhabitat, dwelling on boulders and sheltering in crevices. The lizard also evolved traits important for rock dwelling, such as a flatter skull and shorter legs for skittering into crevices at the first sign of a predator. In other words, the same behavioral switch to boulders that halted physiological evolution also promoted morphological evolution. In the context of global climate change, these findings suggest that the effects of rising temperatures won’t be limited to directly impacting organisms’ physiology—because of their behavior, it could indirectly impact other features, like their morphology, as well. Such predictions, however, would not have been likely without this new understanding of the multidimensional ways in which behavior impacts evolution. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Behavioral drive meets behavioral inertia: One behavior has different evolutionary effects on physiology and morphology </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>volution can be both stimulated and halted by an animal’s behavior, according to a groundbreaking study led by a Virginia Tech researcher. It just depends which trait you’re talking about. </p><p>The study, appearing in <i>The&nbsp;American Naturalist</i>, shows that behavior can be both a brake and a motor for evolution in a manner where slowing evolution in one trait actually requires accelerating evolution in another, according to Martha Muñoz, a new assistant professor at Virginia Tech, and Jonathan B. Losos of Harvard. Understanding this delicate stop-and-go dance can help scientists predict how animals will adapt to global change such as climate change and habitat degradation. </p><p>In the case of the anole lizard of the Dominican Republic, thermoregulation—or the ability to control one’s own body temperature—is crucial to survival. Although it is located in the tropics, the Dominican Republic has lots of mountainous habitat and high elevations that challenge animals like lizards, which cannot regulate their temperature internally, the way that birds and mammals (including people) do. </p><p>When the lizards migrated from warm, low elevations to cool, high elevations, body temperature regulation required the lizard to take up a new microhabitat, dwelling on boulders and sheltering in crevices. The lizard also evolved traits important for rock dwelling, such as a flatter skull and shorter legs for skittering into crevices at the first sign of a predator. In other words, the same behavioral switch to boulders that halted physiological evolution also promoted morphological evolution. </p><p>In the context of global climate change, these findings suggest that the effects of rising temperatures won’t be limited to directly impacting organisms’ physiology—because of their behavior, it could indirectly impact other features, like their morphology, as well. Such predictions, however, would not have been likely without this new understanding of the multidimensional ways in which behavior impacts evolution. <a href="http://dx.doi.org/10.1086/694779">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 20 Oct 2017 05:00:00 GMT “Seasonality rate alters acclimation of performance under climate change” http://amnat.org/an/newpapers/DecNilsOrt.html Acclimation is more beneficial when seasonal changes in temperature are slow Many plants and animals can fine-tune their physiology with the changing seasons. This type of flexibility, known as acclimation, enables individuals to move, feed, and grow better in the cold of winter and in the warmth of summer. Previously, acclimation was believed to be more beneficial in highly seasonal environments near the poles. However, new research performed at Umeå University has revealed that acclimation is especially advantageous in the gently changing seasons at mid-latitudes. In their earlier work, Viktor Nilsson-Örtman and Frank Johansson had noted how high-latitude environments warm up faster in spring and cool down faster in fall compared to lower-latitude environments. Previous research had shown that acclimation is a relatively slow process. This inspired the question: could temperatures change so rapidly over the year at high latitudes that it prevents individuals from acclimating? To answer this question, the researchers reared larval damselflies – small and slender relatives of dragonflies – under the slowly changing seasons typical of central Europe and the rapidly changing seasons typical of northern Sweden. By comparing how different species grew in each climate with predictions from a theoretical model, they found that acclimation was indeed less successful when the seasons changed as rapidly as in northern Sweden. In other words, when temperatures change slowly, it pays off to change with the seasons. But when temperatures change fast, as in northern Sweden, damselflies cannot keep up, so their physiology remain relatively unchanged throughout the year. These results indicate that mid-latitude climates favor species that are physiologically more flexible than tropical and polar climates. They also highlight how climate change can have consequences for biodiversity not only by increasing the earth’s temperature, but by changing the timing of the seasons. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Acclimation is more beneficial when seasonal changes in temperature are slow </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 plants and animals can fine-tune their physiology with the changing seasons. This type of flexibility, known as acclimation, enables individuals to move, feed, and grow better in the cold of winter and in the warmth of summer. Previously, acclimation was believed to be more beneficial in highly seasonal environments near the poles. However, new research performed at Umeå University has revealed that acclimation is especially advantageous in the gently changing seasons at mid-latitudes. </p><p>In their earlier work, Viktor Nilsson-Örtman and Frank Johansson had noted how high-latitude environments warm up faster in spring and cool down faster in fall compared to lower-latitude environments. Previous research had shown that acclimation is a relatively slow process. This inspired the question: could temperatures change so rapidly over the year at high latitudes that it prevents individuals from acclimating? </p><p>To answer this question, the researchers reared larval damselflies – small and slender relatives of dragonflies – under the slowly changing seasons typical of central Europe and the rapidly changing seasons typical of northern Sweden. By comparing how different species grew in each climate with predictions from a theoretical model, they found that acclimation was indeed less successful when the seasons changed as rapidly as in northern Sweden. In other words, when temperatures change slowly, it pays off to change with the seasons. But when temperatures change fast, as in northern Sweden, damselflies cannot keep up, so their physiology remain relatively unchanged throughout the year. </p><p>These results indicate that mid-latitude climates favor species that are physiologically more flexible than tropical and polar climates. They also highlight how climate change can have consequences for biodiversity not only by increasing the earth’s temperature, but by changing the timing of the seasons. <a href="http://dx.doi.org/10.1086/694412">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 18 Oct 2017 05:00:00 GMT “Is plant fitness proportional to seed set? An experiment and a spatial model” http://amnat.org/an/newpapers/Dec17Campbell.html Relative fitness is modified by sib interactions taking place between seed dispersal and juvenile recruitment Ever since Darwin, scientists have studied natural selection on the extraordinary diversity of flower traits seen in nature, often using the number of seeds to estimate fitness, or at least that portion of fitness obtained as a mother. It stands to reason that a plant that makes more seeds would contribute more offspring to the next generation. But is that contribution to the next generation actually proportional to seed production? Little is known about the link between the number of seeds produced by an individual and number of successful offspring, and there are reasons to suspect that seed production might provide a biased estimate of maternal fitness. In a paper in The American Naturalist, Campbell, from University of California, Irvine, and colleagues Brody, Price, Waser, and Aldridge addressed this gap in knowledge. Using a plant species, scarlet gilia, that they have made a “model system” in four decades of work at the Rocky Mountain Biological Laboratory, they asked, “Does a plant that produces twice as many seeds as its neighbor contribute twice the offspring to the next generation?” In field experiments, they used their natural-history knowledge to mimic natural seed dispersal, and genetic markers to follow the fates of seeds from individual parents. Spatial models showed that relative fitness based on seed number is modified, depending on the extent of competition between sibling seeds versus non-sibling seeds, which in turn depends upon the extent of seed dispersal. Plants that produced twice as many seeds as their neighbor produced fewer than twice the number of recruiting juveniles, as expected from the model. Thus, there was a tradeoff between high seed production and offspring survival, making the intensity of selection on a floral trait likely weaker than investigators have previously thought. Competition and other interactions among siblings may have general effects on evolution of plant traits, and may be particularly important for plants with little multiple mating, low adult density, and low seed dispersal. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Relative fitness is modified by sib interactions taking place between seed dispersal and juvenile recruitment </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>ver since Darwin, scientists have studied natural selection on the extraordinary diversity of flower traits seen in nature, often using the number of seeds to estimate fitness, or at least that portion of fitness obtained as a mother. It stands to reason that a plant that makes more seeds would contribute more offspring to the next generation. But is that contribution to the next generation actually proportional to seed production? Little is known about the link between the number of seeds produced by an individual and number of successful offspring, and there are reasons to suspect that seed production might provide a biased estimate of maternal fitness. In a paper in <i>The American Naturalist</i>, Campbell, from University of California, Irvine, and colleagues Brody, Price, Waser, and Aldridge addressed this gap in knowledge. Using a plant species, scarlet gilia, that they have made a “model system” in four decades of work at the Rocky Mountain Biological Laboratory, they asked, “Does a plant that produces twice as many seeds as its neighbor contribute twice the offspring to the next generation?” In field experiments, they used their natural-history knowledge to mimic natural seed dispersal, and genetic markers to follow the fates of seeds from individual parents. Spatial models showed that relative fitness based on seed number is modified, depending on the extent of competition between sibling seeds versus non-sibling seeds, which in turn depends upon the extent of seed dispersal. Plants that produced twice as many seeds as their neighbor produced fewer than twice the number of recruiting juveniles, as expected from the model. Thus, there was a tradeoff between high seed production and offspring survival, making the intensity of selection on a floral trait likely weaker than investigators have previously thought. Competition and other interactions among siblings may have general effects on evolution of plant traits, and may be particularly important for plants with little multiple mating, low adult density, and low seed dispersal. <a href="http://dx.doi.org/10.1086/694116">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 27 Sep 2017 05:00:00 GMT “Stochastic evolutionary demography under a fluctuating optimum phenotype” http://amnat.org/an/newpapers/DecChevin.html Theoretical analysis of population dynamics and extinction risk caused by random fluctuations of an optimum phenotype Most environments in nature fluctuate in a largely random way, beyond directional trends such as global warming. How do these random environmental fluctuations affect the ecology and evolution of populations, and their joint influence on extinction risk? This is the question that Luis-Miguel Chevin, Olivier Cotto (CNRS researchers at the CEFE in Montpellier), and Jaime Ashander (from UCLA), here address. On the ecological side, stochastic (i.e., random) environments cause fluctuations in population size, which can be large since all individuals in the population are affected by the environment. Importantly, even for fluctuation patterns that allow population to persist on average, a sequence of bad years can lead a particular population to extinction. This is more likely to occur if a bad year is most often followed by another bad year, that is, under large temporal autocorrelation of the environment. On the evolutionary side, a population is more likely to track a moving optimum phenotype by adaptive evolution if the movements of this optimum, despite being random, are still somewhat predictable. This occurs when the environment has high temporal autocorrelation. To combine these ecological and evolutionary effects within a common framework, the authors model the situation where fluctuations in population growth rates depend on the mismatch between the population mean phenotype for a trait and the optimum value for this trait, set by the environment. They use this model to find the distribution of population size, that is, the probability that a population is below or above any given number. They show that this distribution can differ markedly from previous theoretical predictions, most notably by an excess of low population sizes, and thus elevated extinction risk. All parameters of this distribution of population size (its mean, variance among replicate populations, etc…) can be related to basic and measurable parameters of the model, such as the temporal variance and autocorrelation of the optimum, or the genetic variance of the trait. This work thus represents a large step forward in our ability to predict demography and extinction risk of an evolving population in a randomly changing environment. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Theoretical analysis of population dynamics and extinction risk caused by random fluctuations of an optimum phenotype </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 environments in nature fluctuate in a largely random way, beyond directional trends such as global warming. How do these random environmental fluctuations affect the ecology and evolution of populations, and their joint influence on extinction risk? This is the question that Luis-Miguel Chevin, Olivier Cotto (CNRS researchers at the CEFE in Montpellier), and Jaime Ashander (from UCLA), here address. </p><p>On the ecological side, stochastic (i.e., random) environments cause fluctuations in population size, which can be large since all individuals in the population are affected by the environment. Importantly, even for fluctuation patterns that allow population to persist on average, a sequence of bad years can lead a particular population to extinction. This is more likely to occur if a bad year is most often followed by another bad year, that is, under large temporal autocorrelation of the environment. </p><p>On the evolutionary side, a population is more likely to track a moving optimum phenotype by adaptive evolution if the movements of this optimum, despite being random, are still somewhat predictable. This occurs when the environment has high temporal autocorrelation. </p><p>To combine these ecological and evolutionary effects within a common framework, the authors model the situation where fluctuations in population growth rates depend on the mismatch between the population mean phenotype for a trait and the optimum value for this trait, set by the environment. They use this model to find the distribution of population size, that is, the probability that a population is below or above any given number. They show that this distribution can differ markedly from previous theoretical predictions, most notably by an excess of low population sizes, and thus elevated extinction risk. All parameters of this distribution of population size (its mean, variance among replicate populations, etc…) can be related to basic and measurable parameters of the model, such as the temporal variance and autocorrelation of the optimum, or the genetic variance of the trait. This work thus represents a large step forward in our ability to predict demography and extinction risk of an evolving population in a randomly changing environment. <a href="http://dx.doi.org/10.1086/694121">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 27 Sep 2017 05:00:00 GMT “Sex-dependent phenological plasticity in an arctic hibernator” http://amnat.org/an/newpapers/DecWilliams.html Hibernation plasticity in response to extreme weather events differs between the sexes in arctic ground squirrels Climate change can increase the frequency, duration, and intensity of extreme weather, but the degree to which hibernating mammals can buffer themselves from these events by prolonging or re-entering seasonal dormancy is unclear. Using a combination of high-resolution body temperature loggers and snow cover observations, the authors show that female arctic ground squirrels will delay their exit from hibernation, and even re-enter hibernation, in response to unseasonable snow storms in late spring. Extended hibernation by females resulted in a two-week delay in the timing of births. However, what is perhaps most interesting about the findings was the sex-specific response: mature males show no flexibility in timing while immature non-reproductive males respond similarly to females. Sex-dependent plasticity results in a mismatch in timing between the sexes, with males ready to mate weeks before receptive females are available on the surface. These types of sex-specific responses to extreme climate events are likely to have significant consequences for population dynamics, though more work is needed to understand whether late spring snowstorms affect the survival of adult males in the spring or the survival of juveniles during their first winter hibernation. Measuring how seasonal timing is affected by climate change is becoming more common, but this study suggests that measuring timing in both sexes may be needed to fully appreciate how climate change can disrupt biological interactions. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Hibernation plasticity in response to extreme weather events differs between the sexes in arctic ground squirrels </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>limate change can increase the frequency, duration, and intensity of extreme weather, but the degree to which hibernating mammals can buffer themselves from these events by prolonging or re-entering seasonal dormancy is unclear. Using a combination of high-resolution body temperature loggers and snow cover observations, the authors show that female arctic ground squirrels will delay their exit from hibernation, and even re-enter hibernation, in response to unseasonable snow storms in late spring. Extended hibernation by females resulted in a two-week delay in the timing of births. However, what is perhaps most interesting about the findings was the sex-specific response: mature males show no flexibility in timing while immature non-reproductive males respond similarly to females. Sex-dependent plasticity results in a mismatch in timing between the sexes, with males ready to mate weeks before receptive females are available on the surface. </p><p> These types of sex-specific responses to extreme climate events are likely to have significant consequences for population dynamics, though more work is needed to understand whether late spring snowstorms affect the survival of adult males in the spring or the survival of juveniles during their first winter hibernation. Measuring how seasonal timing is affected by climate change is becoming more common, but this study suggests that measuring timing in both sexes may be needed to fully appreciate how climate change can disrupt biological interactions. <a href="http://dx.doi.org/10.1086/694320">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 27 Sep 2017 05:00:00 GMT “A physiological signature of ‘cost of reproduction’ associated with parental care” http://amnat.org/an/newpapers/DecFowler.html Birds pay a cost of reproduction when pushed and now we know the physiological basis of this cost Every parent knows that bringing up children can, at times, be really hard work. But is parental care also hard work for other animals? Could parental care even kill you? And if so how? Melinda Fowler and Tony Williams (2017), of Simon Fraser University, address these questions by making female European starlings work harder while feeding their chicks. They clipped some flight feathers to reduce wing area and attached radio-transmitters to increase body mass. Even though the manipulated females must have had higher flight costs they kept working as hard as other birds, making the same number of visits to the nest to feed chicks, and rearing as many offspring. However, wing-clipped females paid a cost for this parental effort: They did less well in their subsequent breeding attempt and had lower survival to the following year. Moreover, there was a clear physiological signature of this cost females paid. Wing-clipped females had lower oxygen-carrying capacity, lower energy reserves, decreased immune function, and elevated levels of oxidative stress – all signs of poor physiological condition. So hard work during parental care can involve a widespread decline in function across multiple physiological systems: rearing kids could lead to cumulative “wear and tear” on the body and perhaps even decrease lifespan! Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><b>Birds pay a cost of reproduction when pushed and now we know the physiological basis of this cost </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>very parent knows that bringing up children can, at times, be <i>really</i> hard work. But is parental care also hard work for other animals? Could parental care even kill you? And if so how? Melinda Fowler and Tony Williams (2017), of Simon Fraser University, address these questions by making female European starlings work harder while feeding their chicks. They clipped some flight feathers to reduce wing area and attached radio-transmitters to increase body mass. Even though the manipulated females must have had higher flight costs they kept working as hard as other birds, making the same number of visits to the nest to feed chicks, and rearing as many offspring. However, wing-clipped females paid a cost for this parental effort: They did less well in their subsequent breeding attempt and had lower survival to the following year. Moreover, there was a clear physiological signature of this cost females paid. Wing-clipped females had lower oxygen-carrying capacity, lower energy reserves, decreased immune function, and elevated levels of oxidative stress – all signs of poor physiological condition. So hard work during parental care can involve a widespread decline in function across multiple physiological systems: rearing kids could lead to cumulative “wear and tear” on the body and perhaps even decrease lifespan! <a href="http://dx.doi.org/10.1086/694123">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 27 Sep 2017 05:00:00 GMT