Large inversions in Lake Malawi cichlids are associated with habitat, lineage, and sex determination

Large inversions in Lake Malawi cichlids are linked to habitat, lineage, and sex determination, according to a new study. The research utilized long-read technologies to identify four single and two tandem inversions that collectively span over 10% of the genome. These inversions are fixed in one state within each of the seven major ecogroups, indicating their role in the separation of the lake's major lineages into specific habitats.

However, one exception exists in the benthic sub-radiation, where both inverted and non-inverted alleles still coexist. The origins of three of the six inversions suggest they were transferred from the pelagic Diplotaxodon group to benthic ancestors when the benthic sub-radiation first emerged. The remaining three inversions are present in a subset of benthic species living in deep waters.

The study reveals that some of these inversions are associated with XY sex-determination systems, although they appear to be limited to a subset of total lake species. The findings suggest that inversions have been subject to both sexual and natural selection in Lake Malawi cichlids, and they will play a crucial role in understanding the evolution of this adaptive radiation.