The ecological and genetic basis of convergent thick-lipped phenotypes in cichlid fishes

The evolution of convergent phenotypes is one of the most interesting outcomes of replicate adaptive radiations. Remarkable cases of convergence involve the thick-lipped phenotype found across cichlid species flocks in the East African Great Lakes. Unlike most other convergent forms in cichlids, which are restricted to East Africa, the thick-lipped phenotype also occurs elsewhere, e.g. in the Central American Midas Cichlid assemblage. Here we use an ecological genomic approach to study the function, the evolution and the genetic basis of this phenotype in two independent cichlid adaptive radiations on two continents. We applied phylogenetic, demographic, geometric morphometric and stomach-content analyses to an African (Lobochilotes labiatus) and a Central American (Amphilophus labiatus) thick-lipped species. We found that similar morphological adaptations occur in both thick-lipped species and that the ‘fleshy’ lips are associated with hard-shelled prey in the form of mollusks and inve...