Female control of copulations to maximize male help: a comparison of polygynandrous alpine accentors, Prunella collaris, and dunnocks, P. modularis

摘要

Alpine accentors and dunnocks bred in polygynandrous groups in which two or more unrelated males shared two or more females. In both species, a female solicited actively to both alpha and subordinate males whereas an alpha male attempted to guard the female to monopolize paternity. Females combated the restrictions imposed by alpha male guarding by increasing their solicitation rate to males who had gained less mating access. Males increased their copulation rate in response, but alpha males ignored more of the offers. In both species, even when a female mated with both alpha and beta males she often gained just one male's help with chick feeding. Under these conditions, alpha male alpine accentors reduced their amount of help with a decreased mating share, whereas beta males did not. In dunnocks, however, neither alpha nor beta males reduced their help provided a critical share of the matings was exceeded. As predicted if females attempted to maximize male help, female alpine accentors preferred to give more matings to the alpha male while female dunnocks preferred alpha and beta equally. There was no evidence for either species that alpha males sired fitter offspring; within broods of mixed paternity, there was no difference in the weights of chicks sired by alpha versus subordinate males. Female dunnocks competed with other females by territory defence whereas female alpine accentors had overlapping ranges and competed directly for male attention, increasing their solicitation rate to the alpha male if other females in the group were fertile. We suggest that the extraordinarily high rates of solicitation by females, refusal by males and copulation rates (up to a thousand per clutch) in the two species are the outcome of sexual conflict over the control of mating.