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Diversity in aposematic coloration in poison frogs

During my Postdoc at the University of Texas at Austin (2006-2008), I started investigating the evolution of diversity in aposematic (warning) coloration, together with Molly Cummings. We study the extremely colour polymorphic species Dendrobates pumilio. This frog is coloured bright red and blue throughout most of its distributional range (from Nicaragua to Panama), but in the Bocas del Toro Archipelago in western Panama, the species shows extreme colour variation among populations, ranging from orange to yellow to blue, sometimes with black spots or stripes. This variation is probably driven by a combination of natural and sexual selection, possibly interacting with drift in isolated populations. In a series of mate choice experiments, we found that male coloration affects female mate choice, generating not only colour-assortative preferences but also directional sexual selection. Phylogenetic analysis, conducted in collaboration with Kyle Summers and Jason Brown (University of East Carolina, USA), confirmed that colour patterns evolution must have been rapid, implying strong divergent selection. Currently, we are working on the natural selection side of the story, by investigating toxicity variation among frog populations.

PhD research: sexual selection and speciation in Lake Victoria cichlids

University of Leiden, 2006

Thesis advisors: Ole Seehausen and Jacques van Alphen

The haplochromine cichlids of Lake Malawi and Lake Victoria are classic examples of explosive speciation: hundreds of species have evolved very rapidly in both lakes. The widespread occurrence of intra- and interspecific variation in male nuptial coloration and corresponding female mating preferences has inspired the hypothesis that sexual selection has played a major role in the origin of these species flocks. In my PhD project, I used two model systems to test some of the predictions that follow from this hypothesis, and I studied the evolutionary mechanisms that underlie mate choice for colour patterns.

Divergent visual adaptation and sexual selection in cichlid fish

In the cichlid fish of Lake Victoria (East Africa), bright male coloration affects both inter- and intraspecific female mate choice, indicating that sexual selection is important for species differentiation. At the same time, the fish show extensive variation in colour vision, apparently as an adaptation to their diverse visual environments. Possibly, visual adaptation to different light conditions changes female perception of male coloration, such that females that inhabit different light environments will develop different colour preferences.

In my current research, I investigate the role of visual adaptation in cichlid speciation. I use a combination of field observations (characterising under water light conditions and haplochromine colour diversity across communities) and laboratory experiments (testing the effects of visual adaptation on visual behaviour in foraging and mate choice contexts).

For this work I collaborate with Ole Seehausen and Oliver Selz (Eawag and University of Bern) and with Ton Groothuis and Ruth Castillo (University of Groningen).

Research

martine maan

My research is focused on the proximate causes and ultimate consequences of diversity in animal visual signals. I am particularly interested in the role of sexual communication in generating and maintaining species boundaries, and the contributions of both natural and sexual selection to these processes. I study two colourful model systems: cichlid fish and poison frogs.

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