African cichlid fishes: Model systems for evolutionary biology

Cichlid fishes (Perciformes: Teleostei) found in the lakes of Africa have served as model systems for the study of evolution. The enormous number of species (1000 in Lake Malawi alone), the great diversity of trophic adaptations and behaviors, and the extreme rapidity of their divergence (<50,000 y for some faunas) single out these organisms as examples of evolution in progress. Because these fishes are confined to discrete lacustrine environments and their origination is bounded by geological features, these groups provide models with which to study evolution. We review theoretical studies and empirical research on the cichlid faunas of Africa to provide a synthetic overview of current knowledge of the evolutionary processes at work in this group. This view provides the critical information needed to formulate and test hypotheses that may permit discrimination among the diverse theories and models that have been advanced to explain the evolution of these fishes.