The importance of reproductive isolation in driving diversification and speciation within Peruvian mimetic poison frogs (Dendrobatidae)

To explain how populations with distinct warning signals coexist in close parapatry, we experimentally assessed intrinsic mechanisms acting as reproductive barriers within three poison-frog species from the Peruvian Amazon belonging to a Müllerian mimetic ring (Ranitomeya variabilis, Ranitomeya imitator and Ranitomeya fantastica). We tested the role of prezygotic and postzygotic isolation barriers between phenotypically different ecotypes of each species, using no-choice mating experiments and offspring survival analysis. Our results show that prezygotic mating preference did not occur except for one specific ecotype of R. imitator, and that all three species were able to produce viable inter-population F1 hybrids. However, while R. variabilis and R. imitator hybrids were able to produce viable F2 generations, we found that for R. fantastica, every F1 hybrid males were sterile while females remained fertile. This unexpected result, echoing with Haldane’s rule of speciation, validated phylogenetic studies which tentatively diagnose these populations of R. fantastica as two different species. Our work suggests that postzygotic genetic barriers likely participate in the extraordinary phenotypic diversity observed within Müllerian mimetic Ranitomeya populations, by maintaining species boundaries

Intraspecific divergence of sexual size dimorphism and reproductive strategies in a polytypic poison frog

Intraspecific variation in body size, both among populations and between sexes, is an important factor influencing life-history strategies. This variation might be the response to different environmental conditions, as well as natural and sexual selection, and can result in differences in behavior and reproductive strategies among populations. Here, we use the dyeing poison frog (Dendrobates tinctorius) as a model to investigate how interpopulation variation in body size and sexual size dimorphism affects reproductive strategies. As body size increased, sexual size dimorphism also increased, i.e., females were larger than males, and more so in populations with overall larger frogs. This indicates that there is a stronger selection for body size in females than in males, likely as a response to divergent reproductive investment between the sexes. Females from larger-bodied populations produced larger clutches, but the overall number of froglets produced per clutch did not differ among populations. We discuss potential causes and mechanisms that might be responsible for the observed divergence in body size, sexual size dimorphism, and reproductive strategies among populations that likely represent local adaptations. Our findings demonstrate the importance of cross-population studies, cautioning against drawing general conclusions about a species’ ecology without accounting for intraspecific variation

Unexpected colour pattern variation in mimetic frogs: implication for the diversification of warning signals in the genus Ranitomeya

Predation is expected to promote uniformity in the warning coloration of defended prey, but also mimicry convergence between aposematic species. Despite selection constraining both colour-pattern and population divergence, many aposematic animals display numerous geographically structured populations with distinct warning signal. Here, we explore the extent of phenotypic variation of sympatric species of Ranitomeya poison frogs and test for theoretical expectations on variation and convergence in mimetic signals. We demonstrate that both warning signal and mimetic convergence are highly variable and are negatively correlated: some localities display high variability and no mimicry while in others the phenotype is fixed and mimicry is perfect. Moreover, variation in warning signals is always present within localities, and in many cases this variation overlaps between populations, such that variation is continuous. Finally, we show that coloration is consistently the least variable element and is likely of greater importance for predator avoidance compared to patterning. We discuss the implications of our results in the context of warning signal diversification and suggest that, like many other locally adapted traits, a combination of standing genetic variation and founding effect might be sufficient to enable divergence in colour pattern

The evolution and ecology of multiple antipredator defences

Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies.ISSN:1010-061XISSN:1420-910

The evolution and ecology of multiple antipredator defences

Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such "defence portfolios" that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies

The evolution and ecology of multiple antipredator defences

Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such "defence portfolios" that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies