Abstract:
Male lance-tailed manakins (Chiroxiphia lanceolata) cooperate in complex courtship displays, but the dominant (alpha) partner monopolizes mating opportunities. This raises the question of why subordinates (betas) cooperate. Three nonexclusive hypotheses explain the adaptive basis of helping behavior by subordinate males: cooperation may increase (1) subordinates' immediate reproductive success, (2) the reproductive success of close relatives, or (3) subordinates' chances of future reproduction. I demonstrated that beta males rarely sired chicks and were unrelated to their alpha partners but received delayed direct benefits from cooperation; betas had an increased probability of becoming an alpha when compared to males that had not been betas. To investigate the mechanism by which betas attain these adaptive benefits, I examined betas' success in replacing their alpha partners both in natural turnover events and when alphas were experimentally removed. Beta males did not consistently inherit alpha roles in the same territories where they served their beta tenure, arguing that queuing for status does not fully explain the benefits of cooperation for betas. Instead, betas may be apprenticing to develop effective and appropriate displays that enhance their subsequent success as alphas. Complex social affiliations appear to mediate selective pressure for cooperation in this species.
