Abstract

Cichlid fishes from Lake Malawi are important food fishes and protein sources for the local population and popular ornamental fish around the world, but they have also been studied by naturalists as a model system for speciation for over a century. While there is genetic evidence for at least three human “species” (Homo sapiens, H. neanderthalensis and H. denisova) originating in the past million years, ongoing explosive speciation in Malawi cichlids has spawned up to a thousand new species. The spectacular speciation rates in Lake Malawi cichlids are among the fastest ever recorded in vertebrates and gave rise to an immense variability in appearance and behaviour, despite very limited genetic differentiation. While some species are eight times larger than others and differ in most aspects of their ecology, the distribution of genetic variation within single species overlaps with the variation between pairs of species – meaning that different taxa share most of their genetic information. In fact, captive crosses between even the most distantly related species yield fertile offspring and there is evidence of extensive hybridization in the wild. In my talk I will give an overview of three years of PhD research, which involved field work in Malawi and genomic analysis of thousands of whole-genome sequenced individuals from hundreds of species. I will focus on the role of chromosomal inversions in species diversification and introduce a spectacular case of repeated evolution across the lake.