The African cichlid fishes are well-known in the field of evolutionary biology as perhaps the most spectacular example of an adaptive radiation. An adaptive radiation describes a group of species that have rapidly diverged, or speciated, from a single ancestor, each of which occupies and is adapted to a distinct ecological niche. Other well-known adaptive radiations include those of two birds, the honeycreepers of Hawaii and Charles Darwin's finches, which occupy several islands in the Galapagos.

The African cichlids are found in the Great Lakes of the Rift Valley of Africa, including Lakes Victoria, Malawi, Tanganyika, Nabugabo, and others. In these lakes, cichlid fishes have undergone an unparalleled radiation. In all, over 1,500 species have evolved over the course of only ten million years, suggesting a truly remarkable rate of speciation.

Four separate genera and over 200 species occur in Lake Victoria alone. This is particularly...