Sympatric speciation suggested by monophyly of crater lake cichlids

THE existence of sympatric speciation—that populations diverge into species in the absence of physical or ecological barriers—is controversial1–6. The East African Great Lakes harbour hundreds of cichlid species representing only a few monophyletic lineages7,8, although palaeolimnological evidence9–11 and local restrictions on species distribution12 suggest that speciation in these lakes could have been allopatric13,14. The case for sympatry in...