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Parasite-driven and immunogenetic diversification in Lake Tanganyika cichlid fishes

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Parasites and the creation of species

One of the central questions of evolutionary biology is how organisms adapt to different environments and form new species. The answer may lie among the cichlid fishes of Lake Tanganyika in east Africa, which represent the most diverse assemblage of vertebrate species on the planet.

Climate Change and Environment

Although the cichlids of the East African Great Lakes are used as a model for research into species, it is still unclear how they have achieved such enormous diversity. The EU-funded CICHLIDWORMS (Parasite-driven and immunogenetic diversification in Lake Tanganyika cichlid fishes) project investigated this conundrum. Researchers studied how different habitats, diets and social interactions might lead to different collections of parasites. Parasites challenge their host's immune system and represent a powerful means of natural selection. Furthermore, parasites may also contribute to sexual selection by affecting their host's immune system, thereby influencing its brightness and colouration. The combined effect of natural and sexual selection on a trait (in this case, the immune system) may have the potential to speed up the process by which new species arise. The CICHLIDWORMS project examined this hypothesis in the Tropheini, a group of cichlids found in Lake Tanganyika. State-of-the-art genomics and data integration techniques were employed to determine whether parasites can accelerate adaptations at the macro-evolutionary and micro-evolutionary levels. At the micro-evolutionary scale, screening of different populations of a single cichlid species (Tropheus moorii) showed there is a seasonal variation with regard to parasite infection. Results indicated that adaption to divergent parasitic communities might help diversification into adaptive radiation, whereby organisms rapidly evolve into a variety of new forms. This new understanding of cichlid evolution will provide important baseline data for future research into this important model system for evolutionary biology. CICHLIDWORMS outcomes will enable scientists to gain a better understanding of the mechanisms driving biological diversity. They will also encourage a greater appreciation of biodiversity by society in general.

Keywords

Lake Tanganyika, evolution, cichlid, natural selection, sexual selection, parasites, trait

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