Cichlids in Lake Tanganyika, Lake Malawi and Lake Victoria provide a research environment for the emergence of specialised species that is virtually unrivalled. The three large East African lakes were formed successively by geological subsidence. Cichlids that originally lived in rivers adapted to the new habitats – ranging from deep-water zones and coastal areas to marshy reed beds. In the process, many different species developed, with a similar species community emerging three times independently of one another. And this occurred in what is, in evolutionary terms, a very short period of time. How did this happen?
To answer this question, Christian Sturmbauer and his team selected cichlid species from each lake that occupied the same ecological niche and therefore had similar jaw shapes. In predatory fish, these are elongated, whereas in herbivorous fish they are broader. The zoologists bred these species and compared gene activity in the developing jaws during embryonic development. “Our research revealed that, in an early phase of speciation through adaptation, so-called ‘alternative splicing’ plays a decisive role,” says Sturmbauer, summarising a key finding of the study, and explains: “This process brings about decisive developmental genetic changes surprisingly quickly in order to – as in our case – produce jaw shapes that allow the animals to specialise in specific food sources in their new habitat.” Pooja Singh, first author of the latest publication, made a significant contribution to these findings as part of her doctoral thesis.
Until now, it was widely assumed in the scientific community that alternative splicing variants were of little significance in rapid morphological change. “We were able to show, however, that this is a highly effective mechanism of evolutionary innovation in functional proteins, particularly at the onset of specialisation. Quantitative changes in gene activity only come to dominate at a later stage during further morphological adaptations,” says Sturmbauer.
Cichlids are top-notch when it comes to adaptation. For example, in Lake Victoria, around 500 new species have evolved in a maximum of 16,000 years, species that are found only there. Christian Sturmbauer and his research group at the University of Graz have been conducting highly successful research into the genetic mechanisms of evolutionary innovation in these fish for many years. The extent to which the findings of the current publication apply generally to the emergence of specialised species will need to be clarified by further studies.
Publication
Ancestral splice variation is a key substrate for rapid diversification in African cichlids
Singh, P., Ahi, E.P., Duenser, A., Durdevic, M., Gessl, W., Schaeffer, S., Gallaun, J., Seehausen, O., and Christian Sturmbauer
PNAS, 12 May 2026, 123 (20) e2516477123, https://doi.org/10.1073/pnas.251647712