Genetic Basis of Adaptive Morphological Radiation in Lake Malawi Cichlid Fishes

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Kocher 9905127 Cichlid fishes have undergone an extraordinary adaptive radiation into more than one thousand species in the lakes of East Africa. Key to their success has been the diversification of their oral jaws, which allows them to adopt specialized modes of feeding. Little is known about the genetic basis for these differences in jaw morphology. How many genes control the differences in oral jaw shape? Are the same genes involved in different structures of the head? What kinds of genes control the shape of the jaw? The genetic factors controlling differences in jaw morphology will be studied in a hybrid cross between two Lake Malawi species with radically different jaws. The morphology of a large family of F2 animals will be characterized and each animal genotyped for 100 DNA markers distributed across the genome. By analyzing the effects of particular marker alleles on jaw shape it will be possible to estimate the number, mode of action (additive or dominant inheritance) and chromosomal position of genes contributing to each aspect of morphology. This knowledge will contribute to the understanding of morphological diversification and its role in these remarkable vertebrate radiations. In addition, many of the genes involved in jaw development in this model system are likely to be involved in the development of jaws in other vertebrates, including humans.