Divergent mating preferences and nuptial coloration in sibling species of cichlid fish

Abstract

Mate choice by female cichlid fish from Lake Victoria plays an important role in speciation and the maintenance of species. Females are expected to select against males that are intermediate in their phenotype during the process of speciation driven by sexual selection. To test this, we hybridized two species of cichlids that differ in male nuptial coloration. Male hybrids were intermediate in nuptial coloration compared to the parental species. Hybrids had a comparable fitness to the parental species and did not suffer from inviability, sterility, skewed sex ratios, reduced survival or reduced growth rates. Females preferred males of their own species over males of the other species. This implies that female mate preference can drive speciation. Females of one species were able to distinguish between males of their own species and hybrid males; females of the other species however, were not able to see this difference. When there is hybridization in nature, for instance when coloration becomes invisible by an increase in turbidity of the water, there would be asymmetrical selection against hybrids. An understanding of these processes is crucial in speciation research and for the maintenance of biodiversity.