Non‐gradual variation in colour morphs of the strawberry poison frog Dendrobates pumilio: genetic and geographical isolation suggest a role for selection in maintaining polymorphism

Abstract

The relative roles that geographical isolation and selection play in driving population divergence remain one of the central questions in evolutionary biology. We approached this question by investigating genetic and morphological variation among populations of the strawberry poison frog, Dendrobates pumilio, in the Bocas del Toro archipelago, Panama. We found significant population genetic structure and isolation by distance based on amplified fragment length polymorphism markers. Snout vent length (SVL), coloration and the extent and size of dorsal black spots showed large variation among the studied populations. Differences in SVL correlated with genetic distance, whereas black spot patterns and other coloration parameters did not. Indeed, the latter characters were observed to be dramatically different between contiguous populations located on the same island. These results imply that neutral divergence among populations may account for the genetic patterns based on amplified fragment length polymorphism markers and SVL. However, selective pressures need to be invoked in order to explain the extraordinary variation in spot size and coverage, and coloration. We discuss the possibility that the observed variation in colour morphs is a consequence of a combination of local variation in both natural selection on an aposematic signal towards visual predators and sexual selection generated by colour morph-specific mate preferences.

Not all colors are equal: predation and color polytypism in the aposematic poison frog Oophaga pumilio

“…One counterargument to the hypothesis that decreased predation pressure would permit the observed higher warning signal diversity in O. pumilio is that other dendrobatids present on the islands do not show the same level of diversity in their warning signal (Summers et al 2003;Rudh et al 2007). A genetic pre-disposition toward phenotypic variability (including warning signal diversity) in O. pumilio, though, may be at least one explanation.…”

“…1), O. pumilio displays a high level of warning signal diversity. This diversity manifests itself in color polytypism across the archipelago and polymorphism in some contact zones and on some islands, most notably on Isla Bastimentos (see plates in Myers and Daly 1983;Rudh et al 2007;Saporito et al 2007a). Over 15 color morphs are present in the archipelago and include disparate colors such as yellow, red, blue, lime green, and bronze among others, with different morphs occurring at times on the same island (Siddiqi et al 2004).…”

“…We also compared attack rates on Isla Colón in the Bocas del Toro Archipelago, to data from mainland Costa Rica where previous studies using clay models were completed. Reduced predation pressure may provide an additional explanation for the increased warning signal diversity observed in O. pumilio in the Bocas del Toro region, especially since increased predation pressure is predicted to decrease warning signal diversity (Puurtinen and Kaitala 2006;Rudh et al 2007;Chouteau and Angers 2012).…”

Dissecting comimetic radiations inHeliconiusreveals divergent histories of convergent butterflies

“…Amplified fragment length polymorphisms (AFLPs) have been shown to provide phylogenetic resolution among recently and rapidly radiating groups in which sequence data have failed (17)(18)(19)(20)(21)(22). The increased resolution of AFLPs is associated with their nuclear genome-wide distribution, which overcomes problems associated with locus-specific effects, and the large number of polymorphisms that can be easily characterized.…”

Morphological and genetic variation of the pine shoot tunnel beetle Placusa pinearum (Staphylinidae) in China

“…Host preference may allow insects to feed more effectively on the host plants, which in turn results in restriction of gene flow between populations and promotes host race formation of the feeding insects (Magalhães et al, 2007). Studies have also suggested that morphological divergence between populations is a result of widespread reproductive isolation and local adaptation (Sota et al, 2007) and may be a starting point of a speciation process (Rudh et al, 2007).…”