Repro­duc­tive isola­tion, the ceased exchange of genetic mater­ial, is crucial for the diver­gence of popula­tions into distinct species. This is commonly facil­i­tated by an extrin­sic physi­cal barrier, but rarely it can also occur devoid of such barri­ers. Whether speci­a­tion proceeds by the same or differ­ent repro­duc­tive isola­tion mecha­nisms under these two geographic scenar­ios remains a matter of debate. We aim to contribute to this funda­men­tal question in biology by taking advan­tage of a model system of speci­a­tion: the Midas cichlid fishes.

Speci­a­tion is the emergence of repro­duc­tive isola­tion mecha­nisms among groups of individ­u­als, which ultimately leads to diver­gence into distinct species. While this is most commonly the result of a physi­cal barrier that prevents the exchange of genetic mater­ial entirely (allopa­try), it can also occur within the same environ­ment devoid of such barri­ers (sympa­try). However, deter­min­ing if the same repro­duc­tive isola­tion mecha­nisms evolve in allopa­try and sympa­try has been diffi­cult, most likely due to the lack of systems, where species with similar genomic backgrounds have evolved under both geographic scenarios.

The Nicaraguan Midas cichlid fishes provide a great study system to inves­ti­gate the evolu­tion of repro­duc­tive barri­ers because this species complex is comprised of closely related sympatric and allopatric species. To date, 13 species of Midas cichlids have been described that inhabit two ancient great lakes and several younger crater lakes that were recently colonized (~2,000 to 20,000 years ago).

This project, super­vised by Hector Fellow Prof. Dr. Axel Meyer, will study differ­ent aspects of repro­duc­tive isola­tion: premat­ing, postmat­ing-prezy­gotic and postzy­gotic isola­tion. By combin­ing behav­ioural, molec­u­lar and devel­op­men­tal approaches, we aim to provide compre­hen­sive insights into differ­ent mecha­nisms of repro­duc­tive isola­tion and will contribute to the under­stand­ing of speci­a­tion – still a funda­men­tal problem in evolu­tion­ary biology.