Similar Levels of Diversity and Population Structure in Superflock and Non-superflock Cichlid Fishes from Lake Victoria, Africa

The haplochromine cichlids of the African Great Lakes have evolved into a spectacularly ecologically diverse 1 800 species. However, even within the same lake, not all cichlid lineages have radiated equally and many lineages have remained relatively species depauperate. Multiple biological factors particular to superflock species have been proposed, one of which is extreme environmental sensitivity (stenotopy) resulting in restricted dispersal, which ultimately fosters microallopatric speciation. We use DNA microsatellite loci to estimate neutral genetic diversity and the level of gene flow among populations of two cichlid species from southern Lake Victoria, Africa: the endemic and stenotopic superflock species Pundamilia nyererei and the non-endemic, widespread species Astatoreochromis alluaudi. The two species have similar levels of overall gene diversity (A. alluaudi H = 0.689; P. nyererei H = 0.737). Both species show limited spatialgenetic structure among individuals. Our findings suggest that contemporary gene flow at small spatial scales may not be very different between these two cichlid species with different ecologies. We suggest that the level of contemporary gene flow at fine spatial scales may not be related to the historical rate of speciation.