Visual communication in East African cichlid fishes : Diversity in a phylogenetic context

The flocks of cichlid fishes in the African Great Lakes are a fascinating system for studies of visual ecology. Separate radiations have produced a diverse flock of several hundred closely related cichlid species in each of the three large lakes (Malawi, Tanganyika and Victoria). Closely related species exhibit a diverse range of color patterns. The three lakes have dramatically different photic environments, from the murky waters of Lake Victoria to the clearer waters of lakes Tanganyika and Malawi. The cichlid species flocks in these lakes therefore offer a unique opportunity to examine the forces driving the evolution of visual sensitivity and communication. In this review, we summarize what is currently known about visual communication in this intriguing system. An especially diverse range of visual sensitivities is found among the species occurring in Lake Malawi. The range of visual sensitivities in Lake Victoria is much narrower, and tends to be at longer wavelengths. These differences suggest an important role for the photic environment in shaping visual sensitivities. There is also evidence for links between color usage and visual sensitivities among the flocks in the different lakes. We discuss the possible relationships between visual sensitivity, ecology, photic environment and color usage, and suggest future work to examine the forces acting on visual communication. There is a special need for studies at finer phylogenetic scales, to quantify the variability of visual sensitivities and color between sister taxa. Such studies will provide insights into the possible role of visual communication in cichlid speciation.