CICHLIDWORMS

Parasite-driven and immunogenetic diversification in Lake Tanganyika cichlid fishes

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 Obiettivo del progetto (Objective)

'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.'

Introduzione (Teaser)

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.

Descrizione progetto (Article)

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.