Abstract
The evolution of Müllerian mimicry is, paradoxically, associated with high levels of diversity in color and pattern. In a mimetic radiation, different populations of a species evolve to resemble different models, which can lead to speciation. Yet there are circumstances under which initial selection for divergence under mimicry may be reversed. Here we provide evidence for the evolution of extensive phenotypic divergence in a mimetic radiation in Ranitomeya imitator, the mimic poison frog, in Peru. Analyses of color hue (spectral reflectance) and pattern reveal substantial divergence between morphs. However, we also report that there is a “transition-zone” with mixed phenotypes. Analyses of genetic structure using microsatellite variation reveals some differentiation between populations, but this does not strictly correspond to color pattern divergence. Analyses of gene flow between populations suggest that, while historical levels of gene flow were low, recent levels are high in some cases, including substantial gene flow between some color pattern morphs. We discuss possible explanations for these observations.
Highlights
Mimicry between unrelated organisms provides an exceptional example of evolution by natural selection [1]
Recent evidence indicates that divergence between some R. imitator morphs may have occurred concurrently with or prior to that between two putative model morphs in one region [9], but broad phylogenetic analyses [5,10] clearly indicate that the basal divergence between R. imitator morphs was preceded by divergence among distinct model species, and that all the R. imitator color pattern morphs are recently diverged members of a southern clade of poison frogs
This supports the hypothesis that R. imitator has undergone unilateral ‘advergence’ to resemble distinct models in different geographic regions, and in a historical sense can be thought of as the mimic rather than the model, even though the distinction between model and mimic is less clear in Mullerian mimicry than Batesian mimicry
Summary
Mimicry between unrelated organisms provides an exceptional example of evolution by natural selection [1]. Recent evidence indicates that divergence between some R. imitator morphs may have occurred concurrently with or prior to that between two putative model morphs in one region [9], but broad phylogenetic analyses [5,10] clearly indicate that the basal divergence between R. imitator morphs was preceded by divergence among distinct model species, and that all the R. imitator color pattern morphs are recently diverged members of a southern clade of poison frogs This supports the hypothesis that R. imitator has undergone unilateral ‘advergence’ (see [11] for a discussion of advergence vs convergence) to resemble distinct models in different geographic regions, and in a historical sense can be thought of as the mimic rather than the model, even though the distinction between model and mimic is less clear in Mullerian mimicry than Batesian mimicry
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