THE EFFECT OF MALE COLORATION ON FEMALE MATE CHOICE IN CLOSELY-RELATED LAKE-VICTORIA CICHLIDS (HAPLOCHROMIS-NYEREREI COMPLEX)

We studied the effect of male coloration on interspecific female mate choice in two closely related species of haplochromine cichlids from L ake Victoria. The species differ primarily in male coloration, Males o f one species are red, those of the other are blue. We recorded the be havioral responses of females to males of both species in paired male trials under white light and under monochromatic light, under which th e interspecific differences in coloration were masked. Females oi both species exhibited species-assortative mate choice when colour differe nces were visible, but chose non-assortatively when colour differences were masked by light conditions. Neither male behaviour nor overall f emale response frequencies differed between light treatments. That fem ale preferences could be altered by manipulating the perceived colour pattern implies that the colour itself is used in interspecific mate c hoice, rather than other characters. Hence, male coloration in haploch romine cichlids does underlie sexual selection by direct mate choice, involving the capacity for individual assessment of potential mates by the female. Females of both species responded more frequently to blue males under monochromatic light. Blue males were larger and displayed more than red males. This implies a hierarchy of choice criteria. Fem ales may use male display rates, size, or both when colour is unavaila ble. Where available, colour has gained dominance over other criteria. This may explain rapid speciation by sexual selection on male colorat ion, as proposed in a recent mathematical model.