Meeting Abstract
Social living, while adaptive in terms of enhanced access to mates and predator avoidance, also comes at a cost in terms of increased competition for resources and limitation regarding an individual’s opportunity to mate. As such, competition in social groups often leads to the formation of dominance hierarchies, established and maintained by agonistic interactions. These hierarchies often serve to ameliorate within-group conflict and reduce the costs of fighting conspecifics. The most frequently studies dominance hierarchies are those observed among males under conventional sex-role mating systems in which reproductive success is highly variable for males. In such situations, females are generally considered to play a passive role, selecting from dominant available males. However, potential exists for females to also compete with each other in these arenas. The cichlid fish Astatotilapia butroni provides an interesting opportunity to study how female competition and male choice are influenced by the operational sex-ratio. In this maternal mouth-brooding lekking species, the females remove themselves from the available breeding population while brooding young in their buccal cavity. This allows us to manipulate the operational sex-ratio while maintaining consistent encounter rates among females as well as between males and females. We find that as the number of available females per male increases, the rate of female directed aggression by females increases, consistent with an increased competition for male mates. Female directed aggression by males also increases, consistent with male choosiness when the number of available females per male increases. These data support a more nuanced interpretation of conventional sex-role theory.
