MEYER, Axel; University of Konstanz, Germany: Integrative Biology and the Diversification of the Cichlid Fish Species Flocks

Cichlid fishes are one of the most species-rich groups of vertebrates. In the three large East-Africa Lakes, Tanganyika, Malawi and Victoria they have formed adaptive radiations that each encompass several hundred endemic species. We have investigated the phylogenetic relationships and phylogeographic patterns among the species of all three species flocks based on molecular phylogenetic markers. The molecular evolutionary relationships reveal that convergence and parallelism in coloration and ecologically pertinent traits such as body and tooth shape are widespread both within and among these species groups. Based on this knowledge we are attempting to characterize genomic and developmental features that might correlate with these repeated patterns of phenotypic diversification. Particular emphasis is placed on the characterization of the genomic architecture of the Hox gene clusters and a set of candidate genes that might be responsible for colorational differences that are observed repeatedly among these three independent radiations of cichlid fishes. The architecture (number of Hox clusters, and presence and absense of orthologous Hox genes) is found to vary among different species of fishes, in contrast to entirely uniform pattern that is found in land-vertebrates. Moreover, the rates of molecular evolution in Hox genes of fishes were found to be significantly faster than those of tetrapods. Differences in copy number and splicing were found in some candidate genes that correlate with colorational differences between different color morphs in polymorphic species.