Female ornamentation and intrasexual competition in the convict cichlid fish (Archocentrus nigrofasciatus)

Female ornamentation is a topic of considerable current interest in evolutionary biology but rigorous empirical studies are still lacking. Until recently, most examples of female ornaments were thought of as nothing more than vestigial male traits. Within the last two decades, many studies have sought to find associations between female ornaments and reproductive success without first testing sexual selection directly. Results showing the use of ornaments during female intrasexual encounters have been reported but are confounded by male-mate choice for those same ornaments. The Convict Cichlid Fish (Archocentrus nigrofasicatus) presents an excellent opportunity to further understand why extravagant female ornaments have evolved in some species. Female convicts have bright orange abdomens and fins during courtship and this trait is lacking entirely in males. Previous experiments suggest that these ornaments are used for female-female agonistic interactions rather than male-mate choice. It was also suggested that females evolved ornaments to compete for males that occupy scarce breeding territories. Laboratory experiments have also shown a strong female preference for large males. Therefore, do females choose males strictly based on size or the territory that they are able to obtain? Wild caught fish were tested in the laboratory for female intrasexual competition and male-mate choice independent of each other using partitioned observation aquaria. Females were size matched and only differed in the amount of natural orange coloration on the abdomen. Female color was found to be highly correlated with dominance behaviors. Female color and male choice was not significant. The operational sex ratio in nature was at unity. Laboratory manipulations to decouple male size and territory quality were performed to measure female preferences. It was found that females preferred large males and high quality breeding territories equally. This suggests that both male size and territory quality are important when choosing a mate. Female ornaments most likely evolved to compete directly with other females for these resources. However, further research is necessary to measure female intrasexual competition in nature. Other species of cichlids provide excellent opportunities for researching female ornamentation and may evidence for natural selection as well as sexual selection for the trait.