This research project considers the genetic mechanisms of vertebrate diversification from two perspectives. The first is that of population genetics. How many genes experience divergent selection during the evolution of new species? How are they distributed across the genome? The second perspective is that of the evolution of development. Which genes are modified to produce new phenotypes? The flock of some 800 closely related cichlids fishes in Lake Malawi are an ideal model system for this study. These species differ in the shape of their jaws and teeth, the color of their skin, and their mechanisms of sex determination.