To test the hypothesis of parallel speciation by sexual selection, we examined length
variation at six microsatellite loci of samples from four sites of four to six putative
species belonging to two subgenera of rocky shore mbuna cichlids from Lake Malawi.
Almost all fixation indices were significantly different from zero, suggesting
that there is presently little or no gene flow among allopatric populations or
sympatric species. Analysis of variance indicated that genetic distances among allopatric
populations of putative conspecifics were significantly lower than among sympatric
populations of heterospecifics. The topology of trees based on distance matrices
was also largely consistent with the hypothesis that the putative species are monophyletic
and have thus not evolved in parallel in their present locations. If parallel
speciation does occur in Malawi cichlids, it may be on a larger spatial scale than
investigated in our study.