How organisms adapt to different environments and form new species is a central question in evolutionary biology. Cichlid fish of the East-African Great Lakes are the most diverse species assemblage of vertebrates on our planet. Even though they have become a model for speciation research, how and why they reached this enormous diversity remains difficult to explain based on current insights. One theory is that cichlids evolved through habitat diversification (e.g. adaptation to a substrate type), trophic diversification (evolution of different feeding strategies and adaptation to a specific diet) and communication diversification (e.g. evolution of different social interactions including colour- and odour-based mate recognition). However, different habitats, diets and social interactions might also lead to exposure to different parasite communities. Parasites challenge their host’s immune system, and represent strong agents of natural selection. Moreover, parasites might also contribute to sexual selection through immunity-based mate choice (which in cichlids is reflected in brightness and coloration). The combined effect of natural and sexual selection on a trait (in this case the immune system) has the potential to accelerate speciation. Therefore cichlid diversification might essentially be parasite-driven, but this hypothesis has received little attention. Here we address this hypothesis in the Tropheini, an endemic cichlid tribe of Lake Tanganyika, and in its genus Tropheus, which radiated into more than hundred color morphs. Based on state-of-the-art training in genomics and data integration, we aim to obtain an unprecedented view on the potential of parasites to accelerate adaptive radiations at the macro-evolutionary level (Tropheini) and at the micro-evolutionary level (Tropheus). This project will greatly contribute to a better understanding of the mechanisms underlying biological diversity, and benefit the societal appreciation of biodiversity.
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