African cichlid fishes: Model systems for evolutionary biology

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