Ecological opportunity and sexual selection together predict adaptive radiation

A fundamental challenge to our understanding of biodiversity is to explain why some groups of species undergo adaptive radiations, diversifying extensively into many and varied species, while others do not. Both extrinsic environmental factors (e.g. resource availability, climate) and intrinsic lineage-specific traits (e.g. behavioural or morphological traits, genetic architecture) influence diversification, but few studies have addressed how such factors interact. Radiations of cichlid fish in the African great lakes provide some of the most dramatic cases of species diversification. However, most cichlid lineages in African lakes have not undergone adaptive radiations. To investigate why adaptive radiation occurs and does not, we compiled data on cichlid colonization and diversification in 46 African lakes, along with lake environmental features and information about the traits of colonizing cichlid lineages. We find that extrinsic environmental factors related to ecological opportuni...