Female nuptial coloration and its adaptive significance in a mutual mate choice system

Adaptive female coloration is likely to occur when males largely invest into reproduction or variance of quality between potential mating partners is high. Although recent studies have shown male choosiness of female traits, little is known about the extent to which female ornamentation signals benefits to males. Female ornamentation might signal individual quality information and thus might be sexually selected by males or play a role in female–female competition. Here, we investigate the role of the female ventral coloration in sexual selection of Pelvicachromis taeniatus, a biparental African cichlid with mutual mate choice. We show that the female ornament 1) is sexually selected by males, who preferred females that showed a larger extent of the nuptially colored area. Female purple coloration, which consists of blue and red color components, 2) transmits information about female quality and ripeness. The magnitude of the red area predicted female readiness to spawn, whereas the extent of the blue area female fecundity, maternal quality, and offspring fitness. Ornamentation 3) is important in female–female competition. Dominance tests conducted under different illumination conditions that maintained or abolished the differences in nuptial coloration suggest that female coloration functions as a threat signal. These results support that female ornamentation may evolve as an indicator of quality through male choice, female–female competition, or both, in a species with mutual mate choice.