The genetic basis of the repeated evolution of an adaptive character: Hypertrophic lips of cichlid fishes

• Applicant: Professor Dr. Gonzalo Machado-Schiaffino, Ph.D.
• Subject Area: Evolutionary Cell and Developmental Biology (Zoology) ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 243870899

Convergent evolution is a well-known phenomenon where unrelated species that live in similar environments evolved similar phenotypic characteristics. However, it is still unclear if phenotypic convergence is produced by the same or different mutations in the same or different genes. Cichlid fishes are famous for their diversity in morphology, coloration, and behaviour and are a well-known textbook model for the study of speciation and adaptive evolution. The occurrence of convergent evolution in several characteristics such as coloration and body shape has also been documented in cichlids inhabiting independent lakes (e.g. African great lakes). Hypertrophic lips are an ecologically important trait related to feeding behaviour in rocky substrates and have evolved repeatedly in parallel in cichlids both in Africa and Central America. This exciting case of repeated evolution is probably due to similar selective pressures associated with foraging behaviour. Since in this case of convergent evolution hypertrophic lips in cichlids evolved repeatedly not only among relatively closely species from Africa, but also in New World cichlids we will be in a unique position to compare the genetic mechanisms at several levels of evolutionary relationships. To investigate these issues, we plan to construct comparative genetic maps using Next Generation Sequencing (NGS) approaches in order to identify the regions in the genomes that are associated with hypertrophic lips. After the regions have been identified, it will be possible to test whether the same gene(s) in different populations and species are causing these similar phenotypic traits. These results will address one of the most important questions in evolutionary biology in the age of genomics: (1) are adaptations the result of mutations at many loci each with small effects or a few loci of large effect? (2) What is the source of adaptive genetic variation (standing genetic variation or new mutations)? (3) Are similar adaptations to similar environmental pressures - i.e. repeated evolution - caused by the same mutations in the same genes or caused by different mutations even in different genes?

• DFG Programme: Research Grants
• Participating Persons: Dr. Paolo Franchini, Ph.D.; Dr. Frederico Henning; Professor Dr. Axel Meyer