Disentangling Female Mate Choice and Male Competition in the Rainbow Darter, Etheostoma caeruleum

Abstract

Sexual selection via female choice is assumed to be common in darters despite few studies demonstrating the phenomenon. This study examines the breeding behaviors of the rainbow darter, Etheostoma caeruleum, and addresses the following four questions: Do females exhibit mating preferences? Which behavioral variables are good measures of female mating preferences? Which male behaviors are used in the context of mating? How do female choice and male competition affect mating success? In dichotomous choice tests, where females could choose between males from two different populations, females performed a precopulatory behavior (nosedigs) significantly more often in front of males from Prairieville Creek than they did in front of males from Seven Mile Creek. However, no pattern of choice was detected when preference was measured as the amount of time spent associated with each male. When the animals were allowed to interact freely, males competed aggressively over the female by chasing and attacking each other. Group spawns occurred where two males mated simultaneously with the female. Male spawning success was positively correlated with male guarding ability (the ability to prevent a competing male from coming between himself and the female). However, there were no significant correlations between overt aggression (chases and attacks) and male spawning success or between female preference (measured in dichotomous choice tests) and male spawning success. Male interactions, in the form of guarding, appear to play a larger role in determining male mating success than does female choice.