Universität Bern
Eawag

African cichlid fish

Ecological Genetics of Speciation and Hybridization

On going projects

Project 1

One of the least understood problems in evolutionary biology and biodiversity research is why some organisms have undergone massive speciation and adaptive diversification within very short time, whereas many others, often closely related and superficially similar, have diversified a lot less. One aspect that is receiving a lot of attention recently is variation among groups of organisms in the propensity to speciate without geographical separation, driven by ecological processes that exert disruptive or diversifying selection. An intensive debate is going on about possible causes of disruptive selection in such speciation scenarios. Diverging mating preferences are assumed in many of the models, and in most speciation scenarios for cichlids in particular. However, it is unclear whether such divergence of mating preferences is recruited by selection resulting from competition for ecological resources or by selection resulting from competition for mating opportunities, followed by ecological character displacement. In this project we aim at developing experimental tests of predictions made by alternative speciation models with regard to the emergence of gene associations comprising alternative sets of genes. We are using hybridizing morphs or incipient species of Lake Victoria cichlids to (i) subject different classes of traits to tests of disruptive selection, and (ii) to identify chromosomal linkage groups containing “speciation traits” by association scans with AFLP markers. 

  • Contact person: Isabel Magalhaes, Ole Seehausen
Project 2

Another unresolved problem associated with the rapid emergence of adaptive diversity is the source of genetic variation that endows some lineages with unusually high rates of phenotypic evolution. One idea is that hybridization between genetically well differentiated lineages endows hybrid populations with large variation in quantitative traits that allows them to radiate in response to diversifying selection when the opportunity is there, such as in novel or perturbed environments. In this project we use experimental ecological genetics to test predictions of this hypothesis. We investigate morphological and ecological diversity generated experimentally by interspecific hybridization, as well as hybrid viability and fertility to experimentally parameterise intrinsic and ecological hybrid fitness and functional hybrid diversity in relation to genomic and ecological distinctiveness of parental species.

  • Contact person: Rike Stelkens, Ole Seehausen