Male competition and female choice interact to determine mating success in the bluefin killifish

Whether male competition and female choice act in concert, independently, or in opposition is a critical issue for understanding sexual selection. In complex social systems, the outcomes of pairwise interactions may not be accurate indicators of how sexual selection emerges. We investigated how female choice and male competition interact in the bluefin killifish, Lucania goodei, in a 3-staged experiment where 1) females could choose between 2 males, 2) those males could interact in the presence of that female, and 3) females and males could freely interact and spawn. In the pairwise stages (1 and 2), females displayed pronounced preferences between males and male competition produced a distinctly dominant individual. None of the morphological traits, including color, measured in males were associated with either female preference or male dominance. When all 3 fish interacted (stage 3), male activity level was the sole predictor of spawning success. Males with elevated activity levels were more aggressive toward males and females, exhibited intensified courtship, and obtained more spawns. Female preference did not predict the number of spawns with a male, but it did predict her latency to spawn; females spawned more quickly with preferred males. Thus, male competition and female choice interact to determine reproductive success, but there is evidence for conflict and a cost to females of associating with dominant males. Reproductive success in this species is not easily predicted from simple measures of morphology or female preference and is influenced by complex social interactions, both between males, and between males and females.