Tests of the kin selection model of mate choice and inbreeding avoidance in satin bowerbirds

Abstract

In typically outbreeding species, females can avoid a reduction in offspring fitness by choosing unrelated sires. However, the kin selection model of mate choice suggests that it may be adaptive to mate with relatives to gain inclusive fitness benefits, especially in lekking species. Several studies have shown that females tend to mate with relatives, but the detailed behavioral data necessary to determine whether this reflects an active preference is difficult to acquire. We test the hypotheses that females actively preferred or avoided relatives in mate choice in satin bowerbirds (Ptilonorhynchus violaceus), a lekking species in which comprehensive observations of natural mate choice were obtained using automated video cameras positioned at bowers. We identified specific males that were sampled by individual females and assessed whether relatedness influenced their acceptance or rejection as mates. We found no consistent effect of relatedness on mate choice across years or among multiple stages of mate choice. In 2 of 6 years, females copulated with relatives at or above the half-sibling level significantly more often than expected, but this was attributed to females searching for mates in areas populated by relatives, and not to an active preference for relatives. Furthermore, we found no evidence for inbreeding avoidance through mate choice discrimination or sex-biased dispersal.