Replicated evolution of trophic specializations in an endemic cichlid fishlineage from Lake Tanganyika

The current phylogenetic hypothesis for the endemic Lake Tanganyika cichlid fishes of the tribe Eretmodini is based solely on morphology and suggests that more complex trophic morphologies derived only once from a less specia lized ancestral condition. A molecular phylogeny of eretmodine cichlids bas ed on partial mitochondrial DNA cytochrome b and control-region sequences w as used to reconstruct the evolutionary sequence of trophic adaptations and to test alternative models of morphological divergence. The six mitochondr ial lineages found disagree with the current taxonomy and the morphology-ba sed phylogeny. Mitochondrial lineages with similar trophic morphologies are not grouped monophyletically but are typically more closely related to lin eages with different trophic phenotypes currently assigned to other genera. Our results indicate multiple independent origins of similar trophic speci alizations in these cichlids. A pattern of repeated divergent morphological evolution becomes apparent when the phylogeography of the mitochondrial ha plotypes is analyzed in the context of the geological and paleoclimatologic al history of Lake Tanganyika. In more than one instance within Lake Tangan yika, similar morphological divergence of dentitional traits occurred in sy mpatric species pairs. possibly, resource-based divergent selective regimes led to resource partitioning and brought about similar trophic morphologie s independently and repeatedly.