Understanding how species form is a central goal for understanding how biodiversity is generated. Speciation may be driven by many causes, for example, by adaptation of a single species to distinct environments, a process known as ecological speciation. A mimetic radiation (when a single species adaptively radiates to resemble distinct model species) represents an ideal scenario for studying ecological speciation. We have identified a mimetic radiation in a species of Peruvian poison frog, Ranitomeya imitator, that has undergone divergence in color pattern to mimic four unrelated model species. The goal of this project is to assess whether mimetic divergence has led to reproductive isolation among different mimetic morphs of R. imitator. To test this, this project will assess reproductive isolation between mimetic morphs using a combination of population genetic analyses, mate choice experiments, and analyses of advertisement calls. This project may help elucidate whether ecological speciation occurs in a predictable way by identifying whether morphological divergence is a predictor of reproductive isolation. The study species, Ranitomeya imitator, has been highly publicized recently for its remarkable parental care strategies, both by the BBC (?Life in Cold Blood? series) and by the NHK (Japanese Broadcasting Corporation, currently in production). However, surprisingly little has been made about this species? fascinating mimicry system, which may be because this aspect of the species has barely been studied. As mimicry provides such a visually powerful example of natural selection, this research may help bring this aspect of this species? biology to the public eye.
A major goal of biology is to understand how species form, and thus get a better understanding of the patterns that shape global biodiversity. One way new species can form is when different populations of a single species adapt to distinct ecological conditions. Under certain circumstances, differential adaptation can lead to reproductive isolation between populations, a process known as "ecological speciation". For this project, we studied a species of poison frog in order to understand how divergence in mimetic color patterns in these frogs can lead to early-stage speciation among different populations. To do this, we studied the poison frog species Ranitomeya imitator, which lives in the rainforest of central Peru. This species is remarkable in that it has four distinct color pattern morphs, all of which resemble an unrelated poison frog species, in what appears to be a case of mimicry. We studied how mimetic adaptations can lead to reproductive isolation, and possibly speciation, between different mimetic morphs. We found that, in one case, two mimetic morphs share a narrow hybrid zone, indicating incomplete reproductive isolation. However, we found that one of the mimetic morphs preferentially mates with members of its own morph, which may be a key early step in the speciation process. Furthermore, it appears that there has been a breakdown of gene flow between the two morphs, something that is expected in the early stages of ecological speciation. These results are interesting in that they relate mimicry, which is a visually compelling example of natural selection, to speciation. Here, we can actually see the traits subject to divergent selection for mimicry, providing a unique demonstration of how differential adaptation can result in speciation. Furthermore, poison frogs themselves are a remarkable group of animals that are, in many ways, emblematic of tropical biodiversity. Here, we are able to see that the bright color patterns themselves may play a role in generating some of this biodiversity.
