Inferring the role of sexual and natural selection in speciation by studying genomics of colouration in strawberry poison frogs

Background

Animal populations that use different adaptive strategies are an ideal study system to uncover processes involved in early stages of speciation. The aim of this study is to understand the interplay of natural and sexual selection in generating biological diversity by using strawberry poison frogs as a study system. Theses amphibians are widely distributed in the Bocas del Toro archipelago in Panama and show a remarkable colour polymorphism, with up to 18 different colour morphs occurring in sympatry and allopatry. To avoid predation, the frogs adapt one of two strategies: aposematism (conspicuous warning colouration) or crypsis (inconspicuous colouration that blends in with surroundings). Because strawberry poison frog morphs mate assortatively, differences in coloration driven by natural selection (the predator avoidance strategy) may interact with sexual selection (preference for morphs of the same colour as oneself) and promote population differentiation. Thus, this study system offers a unique opportunity to investigate evolutionary forces that are at play in the early stages of speciation. 

Key research questions

This project will make use of genomic and transcriptomic data to study demography, population differentiation, and the genomic basis of colouration in multiple cryptic and aposematic strawberry poison frog populations. Research questions include: 

• What is the genomic basis of crypsis and aposematism? Is colouration determined by a few loci or does it require changes in many genes? The genomics of colouration will determine the complexity of switching between predator avoidance strategies, which appear to have happened repeatedly in this species.
• What are the underlying changes in gene expression involved in generating colour polymorphism within the different strategies? How is the colour perceived and processed?
• Does population history/demography play a role in the predator avoidance strategy? Previous studies suggest that the variation in colouration among populations have occurred through repeated loss of aposematism. Could this loss be associated with population bottlenecks? Drift (particularly if colouration is based on few loci) or negative selection in small populations where educating predators to avoid aposematic prey is not successful, could be the driving forces.

Methodology

The project relies on a comprehensive transcriptomic dataset of several frog tissues, including skin, liver, eye and brain and shotgun DNA data generated from muscle. This is primarily a computational project that will use publicly available and newly generated genomic resources to study population differentiation, population history, and gene expression. It will be conducted in collaboration with researchers in the UK, Sweden and Germany. 

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