Using phylogenies to test evolutionary hypotheses about cichlid fishes

Cichlid fishes provide a remarkable example of explosive speciation and adaptive radiation. Consequently, the phylogenetic relationships of these fishes have attracted a great deal of attention from biologists. Over a century of morphological investigation into the evolutionary relationships of cichlids has recently been augmented and refined by a proliferation of new data based on molecular genetic techniques. In this review, we first present the key morphological and molecular studies of cichlid relationships. Second, we explain how such evolutionary frameworks can be incorporated into the study of the behaviour, ecology and evolution of these fishes. Several comparative methods are described that are used to identify independent evolutionary events and make statistically valid comparisons. Three examples show how these techniques have been used to study cichlid evolution. We argue that even if one is not interested in evolutionary relationships themselves, an understanding of such relationships is vital for testing hypotheses about morphology, life histories and behaviour.