Female mosquitofish (Gambusia affinis holbrooki) prefer normally pigmented males to melanistic males

Some mosquitofish (Gambusia affinis holbrooki) populations contain strikingly pigmented melanistic males that are always quite rare (<3% of males). Female mating preferences have been suggested to contribute to the maintenance of the melanistic trait. The investigators studied female preferences for normally pigmented vs. melanistic males using a visual-cue preference apparatus. Stimulus animals varied in population of origin and degree of melanism. Females consistently preferred normally pigmented males. In addition, females that had interacted with melanistic males prior to testing showed an increased avoidance of melanistic males. The authors conclude that female preferences for the melanistic phenotype are unlikely to contribute to the maintenance of the melanistic trait and may in fact help explain its rarity.