Assessing the dual utility of nuptial patterning in the rainbow darter (Etheostoma caeruleum)

Kara M Million, Yseult Héjja-Brichard, Mamoona Nasir, Shreya Tuckley, Tamra C Mendelson

In this study, we assessed the possible dual utility of nuptial color patterns in male rainbow darters (Etheostoma caeruleum) in the context of male-male territorial interactions and female mate choice. Using a cohort of wild-caught male E. caeruleum, we conducted simulated territorial contests between pairs of males in the lab. We scored the “winner” and the “loser” of each contest based on behaviors and color changes at the end of each contest. We then performed dichotomous choice trials using the same pairs of males as stimuli and female E. caeruleum as focal subjects. We scored the choice trials based on the female strength of preference. We assigned each male an Elo rating (a relative skill score used in zero-sum contests between pairs of players) in the male-male contests based on wins and losses, and in the choice trials based on female preference across all trials for each male. We evaluated whether success in male-male contests correlated with success in female choice trials. Finally, we measured body area, mean luminance and luminance contrast for each male, and we evaluated whether either variable correlated with success in male-male contests or in female choice trials. We did not find a statistically significant correlation between Elo ratings in the contests and those in the choice trials, although we observed a positive trend in the relationship. Neither body area nor mean luminance was significantly correlated with success in either set of trials, and luminance contrast was positively correlated with success only in the female choice trials. Our findings indicate that the vivid patterns in breeding male E. caeruleum may play a role in female mate choice. This study highlights the importance of evaluating the role of conspicuous nuptial characteristics in both intrasexual and intersexual selection.