The resident's dilemma: a female choice model for the evolution of alternative mating strategies in lekking male ruffs (Philomachus pugnax)

Previous models for the evolution of alternative male mating behavior have virtually ignored the role of female choice. We present a model in which female choice favors the evolution and maintenance of alternative mating strategies in male ruffi, Philomachus pugnax. Resident male ruffe establish and defend courts on leks against other residents, while non-territorial satellite males move between leks and among courts on a lek. Residents appear to actively recruit satellites to their courts, even though satellites may mate with females once there. Resident behavior toward satellites and data on female behavior suggest that residents benefit from a satellite's presence due to some female preference for mating on co-occupied courts. However, if aD residents accept satellites, none gains any relative advantage, yet all pay the costs of having satellites on their court. We present a game theoretical model that shows that the relative nature of female choice places residents in an evolutionary dilemma with respect to satellite acceptance. Although all residents would benefit if satellites could be cooperatively excluded from leks, the only evolutionarily stable strategy for individual residents is to defect and accept satellites. The model also demonstrates that this "resident's dilemma" likely exists only in a local sense, since the failure of residents to cooperatively exclude satellites from leks need not result in globally lower payoffs, due to frequency-dependent selection on the proportion of satellites in the population. Our analysis suggests that the resident-satellite relationship in ruffs, despite its obvious competitive elements, is fundamentally a cooperative association favored by female choice. Female choice has also been proposed as the primary mechanism selecting for male association to form leks in ruffe. In this context, resident-satellite associations may be thought of as transitory "leks within a lek." Key xoords: alternative mating strategies, cooperation, female choice, game theory, leks, Philomachus pugnax, polymorphism, prisoner's dilemma, ruffs, sexual selection. [Bthav Ecol 8:218-225 (1997)]