derstood in terms of a simple sum of the actions of individuals, whereas groups can possess pheno... more derstood in terms of a simple sum of the actions of individuals, whereas groups can possess phenotypes that simply do not exist at the individual level, such as the level of cohesion in a flock or shoal (Farine,
Aposematic (warning) coloration is a highly conspicuous trait that is found throughout the animal... more Aposematic (warning) coloration is a highly conspicuous trait that is found throughout the animal kingdom. In several aposematic species, warning signals have been co-opted for use in conspecific communication systems; for example, in the toxic and bright orange Solarte population of the strawberry poison frog (Oophaga [Dendrobates] pumilio), the brightness of male warning coloration serves as a sexual signal by both attracting females and repelling rivals. Here, we investigate correlations between bright male warning coloration and several physiological characteristics (e.g., circulating testosterone and carotenoids and noxious alkaloids in the skin), to gain insights into the mechanisms underlying the signal variation in this population and to inform hypotheses regarding the evolutionary stability of this trait. We find that although measures of male brightness (viewer-dependent or viewer-independent) do not correlate with two classic Electronic supplementary material The online version of this article (
Understanding the relative importance of sexual and natural selection in shaping morphological tr... more Understanding the relative importance of sexual and natural selection in shaping morphological traits is a long-standing goal of evolutionary ecology. Male-biased sexual size dimorphism (SSD) is typically associated with male-male competition. Similarly, male polymorphisms are considered a consequence of competitive social interactions. This classic paradigm overlooks the fact that environmental factors mediate social interactions and can lead to ecological adaptations. Common side-blotched lizards, Uta stansburiana, are a model system for this paradigm due to well-known rock-paper-scissors social dynamics between male morphs. SSD in this species has been considered primarily a consequence of social interactions, with male size resulting from the number of morphs in each population and female size being constrained through fecundity benefits. We test if the environment explains intraspecific variation in SSD and number of male morphs in U. stansburiana. By compiling data from 49 populations, we show that environmental variables are stronger predictors of SSD than the number of male morphs. Similarly, we show that the environment mediates SSD and potentially contributes to morph loss in colder environments. We propose that the environment favours smaller males in areas of high seasonality. Our results demonstrate the importance of the environment as a mediator of SSD.
Colour is an important component of many different defensive strategies, but signal efficacy and ... more Colour is an important component of many different defensive strategies, but signal efficacy and detectability will also depend on the size of the coloured structures, and how pattern size interacts with the background. Consequently, size‐dependent changes in colouration are common among many different species as juveniles and adults frequently use colour for different purposes in different environmental contexts. A widespread strategy in many species is switching from crypsis to conspicuous aposematic signalling as increasing body size can reduce the efficacy of camouflage, while other antipredator defences may strengthen. Curiously, despite being chemically defended, the gold‐striped frog (Lithodytes lineatus, Leptodactylidae) appears to do the opposite, with bright yellow stripes found in smaller individuals, whereas larger frogs exhibit dull brown stripes. Here, we investigated whether size‐dependent differences in colour support distinct defensive strategies. We first used visual modelling of potential predators to assess how colour contrast varied among frogs of different sizes. We found that contrast peaked in mid‐sized individuals while the largest individuals had the least contrasting patterns. We then used two detection experiments with human participants to evaluate how colour and body size affected overall detectability. These experiments revealed that larger body sizes were easier to detect, but that the colours of smaller frogs were more detectable than those of larger frogs. Taken together our data support the hypothesis that the primary defensive strategy changes from conspicuous aposematism to camouflage with increasing size, implying size‐dependent differences in the efficacy of defensive colouration. We discuss our data in relation to theories of size‐dependent aposematism and evaluate the evidence for and against a possible size‐dependent mimicry complex with sympatric poison frogs (Dendrobatidae).
Biological Journal of The Linnean Society, Nov 19, 2019
Anti-predator strategies can influence trade-offs governing other activities important to fitness... more Anti-predator strategies can influence trade-offs governing other activities important to fitness. Crypsis, for example, might make conspicuous sexual display especially costly, whereas aposematism might reduce or remove such costs. We tested for correlates of anti-predator strategy in Oophaga pumilio, a polytypic poison frog with morphs spanning the crypsis–aposematism continuum. In the wild, males of visually conspicuous morphs display from conspicuous perches and behave as if they perceive predation risk to be low. We thus predicted that, given a choice of ambient light microhabitats, these males would use high ambient light conditions the most and be most likely to perch in high-light conditions. We found no evidence that differently colored male O. pumilio preferentially used bright microhabitats or that ambient light influenced perching in a morph-specific manner. Independent of light conditions, males from the most conspicuous population perched the least, but the most conspicuous individuals from a polymorphic population perched the most. These patterns suggest that preferences do not necessarily underlie among-morph differences observed in the wild. This could be explained, and remain consistent with theory, if risk aversion is shaped, in part, by experience.
Color patterns can serve a variety of antipredator functions (Cuthill et al., 2017). Cryptic colo... more Color patterns can serve a variety of antipredator functions (Cuthill et al., 2017). Cryptic coloration can reduce the likelihood of detection and subsequently lower the risk of predation (Cuthill, 2019; Merilaita et al., 2017). Meanwhile, aposematic coloration reduces predation risk by utilizing memorable phenotypic traits in conjunction with a form of defense which renders prey unpalatable (Caro &
Abstract Threats to biodiversity have necessitated the implementation of timely conservation stra... more Abstract Threats to biodiversity have necessitated the implementation of timely conservation strategies. Negative anthropogenic impacts on species classically include habitat modification, fragmentation or loss. However in addition to these some species face additional risks such as those associated with (illegal) unsustainable harvests related to private collection, trade and commerce. Although commerce in plants and animals has a long history, recent findings suggest that online networking enhances connectivity between wildlife vendors and collectors, and can catalyze demand. In recent years conservation organizations have turned to biocommerce to offer legal and sustainable alternatives to smuggled or wild collected species. Here we provide a compendium of considerations related to the ethics and application of biocommerce in wildlife using case studies of two highly collected groups of tropical organisms; neotropical orchids and poison frogs. While we are in favor of biocommerce due to benefits such as the potential to mitigate unsustainable wildlife trade and provide funding for conservation programs, we also feel it is timely to provide an important overview detailing historical shortcomings in sustainability, and attempt to provide an ethical compass facilitating the future fusion of conservation and exotic hobbies.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Because variation in warning signals slows down the predator education process, aposematic theory... more Because variation in warning signals slows down the predator education process, aposematic theory predicts that animal warning signals should be monomorphic. Yet, warning color polytypisms are not uncommon in aposematic species. In cases where warning signal variants are separated geographically, adaptation to local predators could explain this variation. However, this cannot explain the persistence of sympatric polymorphisms in aposematic taxa. The strawberry poison frog (Oophaga pumilio) exhibits both allopatric and sympatric warning color variation in and around the Bocas del Toro archipelago of Panama. One explanation that has been proposed for the rapid diversification of O. pumilio coloration in this archipelago is low predation; if island populations have few predators, stabilizing selection would be relaxed opening the door for diversification via selection or genetic drift. Using a combination of mark-recapture and clay model studies, we tested for differences in survival and predation among sympatric red and yellow color morphs of O. pumilio from Bastimentos Island. We found no evidence for differential survival or predation in this population, despite the fact that one morph (red) is more common and widely distributed than the other (yellow). Even in an area of the island where the yellow morph is not found, predator attack rates were similar among morphs. Visual modeling suggests that yellow and red morphs are distinguishable and conspicuous against a variety of backgrounds and by viewers with different visual systems. Our results suggest that general avoidance by predators of red and yellow, both of which are typical warning colors used throughout the animal kingdom, may be contributing to the apparent stability of this polymorphism.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Our contemporary understanding of the evolution of bright and conspicuous color patterns is roote... more Our contemporary understanding of the evolution of bright and conspicuous color patterns is rooted in the work of the early pioneers of evolutionary themes such as natural selection. Charles Darwin developed the theory of sexual selection to explain the presence of conspicuous ornamentation, but realized it could not account for the presence of bright colors in nonreproductive Lepidopteran larvae
Warning signals are often characterized by highly contrasting, distinctive and memorable colors. ... more Warning signals are often characterized by highly contrasting, distinctive and memorable colors. Both chromatic (hue) and achromatic (brightness) contrast contribute to signal efficacy, making longwave colored signals (red and yellow) that generate both chromatic and achromatic contrast common. Shortwave colors (blue and ultraviolet) do not contribute to luminance perception, yet are also common in warning signals. The presence of UV aposematic signals is paradoxical as UV perception is not universal, and evidence for its utility is at best mixed. We used visual modeling to quantify how UV affects signal contrast in aposematic butterflies and frogs. We found that UV only appreciably affected visual contrast in the butterflies. As the butterflies, but not the frogs, have UV-sensitive vision these results support the notion that UV reflectance is associated with intraspecific communication, but appears to be non-functional in frogs. Consequently, we should be careful when assigning a selection-based benefit from UV reflectance. Introduction: Our contemporary understanding of the evolution of bright and conspicuous color patterns is rooted in the work of the early pioneers of evolutionary themes such as natural selection. Charles Darwin developed the theory of sexual selection to explain the presence of conspicuous ornamentation, but realised it could not account for the presence of bright colors in non-reproductive Lepidopteran larvae (Darwin 1871). Alfred Russel Wallace, on the other hand, was skeptical of sexual selection and instead built on the work of John Jenner Weir and Henry Walter Bates, to outline a theory of aposematic warning signals, that was later developed further by
Biological Journal of The Linnean Society, Aug 28, 2020
Extended phenotypes are traits that exist outside the physical body of organisms. Despite their r... more Extended phenotypes are traits that exist outside the physical body of organisms. Despite their role in the lives of the organisms that express them and other organisms influenced by extended phenotypes, the consistency and covariance with morphological and behavioural traits of extended phenotypes has rarely been evaluated. We repeatedly measured an extended phenotype involved in prey acquisition (web structure) of wild orb-weaving spiders (Micrathena vigorsii), which rebuild their webs daily. We related web structure to behaviours and spider body length. Web diameter and web density were repeatable among individuals, reaction to a predation threat was very marginally so, and response to a prey stimulus and web evenness were not repeatable. Larger spiders spun wider webs, had webs with increased thread spacing, and the spider possibly tended to react more slowly to a predation threat. When a spider built a relatively larger web it was also a relatively less dense and less even web. The repeatability of web construction and relationship with spider body size we found may be common features of intra-population variation in web structure in spiders. By estimating the consistency and covariances of extended phenotypes we can begin to evaluate what maintains their variation and how they might evolve.
derstood in terms of a simple sum of the actions of individuals, whereas groups can possess pheno... more derstood in terms of a simple sum of the actions of individuals, whereas groups can possess phenotypes that simply do not exist at the individual level, such as the level of cohesion in a flock or shoal (Farine,
Aposematic (warning) coloration is a highly conspicuous trait that is found throughout the animal... more Aposematic (warning) coloration is a highly conspicuous trait that is found throughout the animal kingdom. In several aposematic species, warning signals have been co-opted for use in conspecific communication systems; for example, in the toxic and bright orange Solarte population of the strawberry poison frog (Oophaga [Dendrobates] pumilio), the brightness of male warning coloration serves as a sexual signal by both attracting females and repelling rivals. Here, we investigate correlations between bright male warning coloration and several physiological characteristics (e.g., circulating testosterone and carotenoids and noxious alkaloids in the skin), to gain insights into the mechanisms underlying the signal variation in this population and to inform hypotheses regarding the evolutionary stability of this trait. We find that although measures of male brightness (viewer-dependent or viewer-independent) do not correlate with two classic Electronic supplementary material The online version of this article (
Understanding the relative importance of sexual and natural selection in shaping morphological tr... more Understanding the relative importance of sexual and natural selection in shaping morphological traits is a long-standing goal of evolutionary ecology. Male-biased sexual size dimorphism (SSD) is typically associated with male-male competition. Similarly, male polymorphisms are considered a consequence of competitive social interactions. This classic paradigm overlooks the fact that environmental factors mediate social interactions and can lead to ecological adaptations. Common side-blotched lizards, Uta stansburiana, are a model system for this paradigm due to well-known rock-paper-scissors social dynamics between male morphs. SSD in this species has been considered primarily a consequence of social interactions, with male size resulting from the number of morphs in each population and female size being constrained through fecundity benefits. We test if the environment explains intraspecific variation in SSD and number of male morphs in U. stansburiana. By compiling data from 49 populations, we show that environmental variables are stronger predictors of SSD than the number of male morphs. Similarly, we show that the environment mediates SSD and potentially contributes to morph loss in colder environments. We propose that the environment favours smaller males in areas of high seasonality. Our results demonstrate the importance of the environment as a mediator of SSD.
Colour is an important component of many different defensive strategies, but signal efficacy and ... more Colour is an important component of many different defensive strategies, but signal efficacy and detectability will also depend on the size of the coloured structures, and how pattern size interacts with the background. Consequently, size‐dependent changes in colouration are common among many different species as juveniles and adults frequently use colour for different purposes in different environmental contexts. A widespread strategy in many species is switching from crypsis to conspicuous aposematic signalling as increasing body size can reduce the efficacy of camouflage, while other antipredator defences may strengthen. Curiously, despite being chemically defended, the gold‐striped frog (Lithodytes lineatus, Leptodactylidae) appears to do the opposite, with bright yellow stripes found in smaller individuals, whereas larger frogs exhibit dull brown stripes. Here, we investigated whether size‐dependent differences in colour support distinct defensive strategies. We first used visual modelling of potential predators to assess how colour contrast varied among frogs of different sizes. We found that contrast peaked in mid‐sized individuals while the largest individuals had the least contrasting patterns. We then used two detection experiments with human participants to evaluate how colour and body size affected overall detectability. These experiments revealed that larger body sizes were easier to detect, but that the colours of smaller frogs were more detectable than those of larger frogs. Taken together our data support the hypothesis that the primary defensive strategy changes from conspicuous aposematism to camouflage with increasing size, implying size‐dependent differences in the efficacy of defensive colouration. We discuss our data in relation to theories of size‐dependent aposematism and evaluate the evidence for and against a possible size‐dependent mimicry complex with sympatric poison frogs (Dendrobatidae).
Biological Journal of The Linnean Society, Nov 19, 2019
Anti-predator strategies can influence trade-offs governing other activities important to fitness... more Anti-predator strategies can influence trade-offs governing other activities important to fitness. Crypsis, for example, might make conspicuous sexual display especially costly, whereas aposematism might reduce or remove such costs. We tested for correlates of anti-predator strategy in Oophaga pumilio, a polytypic poison frog with morphs spanning the crypsis–aposematism continuum. In the wild, males of visually conspicuous morphs display from conspicuous perches and behave as if they perceive predation risk to be low. We thus predicted that, given a choice of ambient light microhabitats, these males would use high ambient light conditions the most and be most likely to perch in high-light conditions. We found no evidence that differently colored male O. pumilio preferentially used bright microhabitats or that ambient light influenced perching in a morph-specific manner. Independent of light conditions, males from the most conspicuous population perched the least, but the most conspicuous individuals from a polymorphic population perched the most. These patterns suggest that preferences do not necessarily underlie among-morph differences observed in the wild. This could be explained, and remain consistent with theory, if risk aversion is shaped, in part, by experience.
Color patterns can serve a variety of antipredator functions (Cuthill et al., 2017). Cryptic colo... more Color patterns can serve a variety of antipredator functions (Cuthill et al., 2017). Cryptic coloration can reduce the likelihood of detection and subsequently lower the risk of predation (Cuthill, 2019; Merilaita et al., 2017). Meanwhile, aposematic coloration reduces predation risk by utilizing memorable phenotypic traits in conjunction with a form of defense which renders prey unpalatable (Caro &
Abstract Threats to biodiversity have necessitated the implementation of timely conservation stra... more Abstract Threats to biodiversity have necessitated the implementation of timely conservation strategies. Negative anthropogenic impacts on species classically include habitat modification, fragmentation or loss. However in addition to these some species face additional risks such as those associated with (illegal) unsustainable harvests related to private collection, trade and commerce. Although commerce in plants and animals has a long history, recent findings suggest that online networking enhances connectivity between wildlife vendors and collectors, and can catalyze demand. In recent years conservation organizations have turned to biocommerce to offer legal and sustainable alternatives to smuggled or wild collected species. Here we provide a compendium of considerations related to the ethics and application of biocommerce in wildlife using case studies of two highly collected groups of tropical organisms; neotropical orchids and poison frogs. While we are in favor of biocommerce due to benefits such as the potential to mitigate unsustainable wildlife trade and provide funding for conservation programs, we also feel it is timely to provide an important overview detailing historical shortcomings in sustainability, and attempt to provide an ethical compass facilitating the future fusion of conservation and exotic hobbies.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Because variation in warning signals slows down the predator education process, aposematic theory... more Because variation in warning signals slows down the predator education process, aposematic theory predicts that animal warning signals should be monomorphic. Yet, warning color polytypisms are not uncommon in aposematic species. In cases where warning signal variants are separated geographically, adaptation to local predators could explain this variation. However, this cannot explain the persistence of sympatric polymorphisms in aposematic taxa. The strawberry poison frog (Oophaga pumilio) exhibits both allopatric and sympatric warning color variation in and around the Bocas del Toro archipelago of Panama. One explanation that has been proposed for the rapid diversification of O. pumilio coloration in this archipelago is low predation; if island populations have few predators, stabilizing selection would be relaxed opening the door for diversification via selection or genetic drift. Using a combination of mark-recapture and clay model studies, we tested for differences in survival and predation among sympatric red and yellow color morphs of O. pumilio from Bastimentos Island. We found no evidence for differential survival or predation in this population, despite the fact that one morph (red) is more common and widely distributed than the other (yellow). Even in an area of the island where the yellow morph is not found, predator attack rates were similar among morphs. Visual modeling suggests that yellow and red morphs are distinguishable and conspicuous against a variety of backgrounds and by viewers with different visual systems. Our results suggest that general avoidance by predators of red and yellow, both of which are typical warning colors used throughout the animal kingdom, may be contributing to the apparent stability of this polymorphism.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Our contemporary understanding of the evolution of bright and conspicuous color patterns is roote... more Our contemporary understanding of the evolution of bright and conspicuous color patterns is rooted in the work of the early pioneers of evolutionary themes such as natural selection. Charles Darwin developed the theory of sexual selection to explain the presence of conspicuous ornamentation, but realized it could not account for the presence of bright colors in nonreproductive Lepidopteran larvae
Warning signals are often characterized by highly contrasting, distinctive and memorable colors. ... more Warning signals are often characterized by highly contrasting, distinctive and memorable colors. Both chromatic (hue) and achromatic (brightness) contrast contribute to signal efficacy, making longwave colored signals (red and yellow) that generate both chromatic and achromatic contrast common. Shortwave colors (blue and ultraviolet) do not contribute to luminance perception, yet are also common in warning signals. The presence of UV aposematic signals is paradoxical as UV perception is not universal, and evidence for its utility is at best mixed. We used visual modeling to quantify how UV affects signal contrast in aposematic butterflies and frogs. We found that UV only appreciably affected visual contrast in the butterflies. As the butterflies, but not the frogs, have UV-sensitive vision these results support the notion that UV reflectance is associated with intraspecific communication, but appears to be non-functional in frogs. Consequently, we should be careful when assigning a selection-based benefit from UV reflectance. Introduction: Our contemporary understanding of the evolution of bright and conspicuous color patterns is rooted in the work of the early pioneers of evolutionary themes such as natural selection. Charles Darwin developed the theory of sexual selection to explain the presence of conspicuous ornamentation, but realised it could not account for the presence of bright colors in non-reproductive Lepidopteran larvae (Darwin 1871). Alfred Russel Wallace, on the other hand, was skeptical of sexual selection and instead built on the work of John Jenner Weir and Henry Walter Bates, to outline a theory of aposematic warning signals, that was later developed further by
Biological Journal of The Linnean Society, Aug 28, 2020
Extended phenotypes are traits that exist outside the physical body of organisms. Despite their r... more Extended phenotypes are traits that exist outside the physical body of organisms. Despite their role in the lives of the organisms that express them and other organisms influenced by extended phenotypes, the consistency and covariance with morphological and behavioural traits of extended phenotypes has rarely been evaluated. We repeatedly measured an extended phenotype involved in prey acquisition (web structure) of wild orb-weaving spiders (Micrathena vigorsii), which rebuild their webs daily. We related web structure to behaviours and spider body length. Web diameter and web density were repeatable among individuals, reaction to a predation threat was very marginally so, and response to a prey stimulus and web evenness were not repeatable. Larger spiders spun wider webs, had webs with increased thread spacing, and the spider possibly tended to react more slowly to a predation threat. When a spider built a relatively larger web it was also a relatively less dense and less even web. The repeatability of web construction and relationship with spider body size we found may be common features of intra-population variation in web structure in spiders. By estimating the consistency and covariances of extended phenotypes we can begin to evaluate what maintains their variation and how they might evolve.
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