DISTRIBUTION OF AND REPRODUCTIVE ISOLATION AMONG COLOR-MORPHS OF A ROCK-DWELLING LAKE VICTORIA CICHLID (HAPLOCHROMIS-NYEREREI) (VOL 5, PG 195, 1996)

The geographical and macro- and microhabitat distribution of and mate recognition among color morphs of a complex of Lake Victoria cichlids were studied. The distribution of most morphs was mutually exclusive, but two morphs overlapped extensively and differed only in microhabita t requirements. Coloration differences between them were inherited, an d wild fishes were homozygous in this respect. Positive morph-assortat ive female mate choice was demonstrated. Over the largest part of thei r common geographical range, intermediate phenotypes are absent and th e two morphs are to be considered two biological species. However, in populations at one end of the range, intermediate phenotypes with cont inuously varying male coloration make up the majority of the individua ls. It is suggested that the status of color morphs as phenotypes of o ne species or as separate biological species is a function of environm ental conditions that vary considerably between the localities. The da ta support the hypothesis that polymorphisms can be a step preceding s peciation in cichlid fish.