Genetic evidence of female philopatry in a socially polyandrous shorebird

Abstract

Sex-biased dispersal plays a key role in shaping population dynamics and genetic structure. Two main hypotheses have been proposed for how territoriality and mating competition impact sex-biased dispersal. Female-biased dispersal is expected in monogamous systems with male resource defense, whereas male-biased dispersal is expected in polygynous systems with male competition over mates. However, patterns of sex-biased dispersal in socially polyandrous species, where females compete for both territories and mates, remain poorly understood. We investigated sex-biased dispersal in 2 polyandrous Jacana species across Central America, the Northern Jacana (Jacana spinosa) and Wattled Jacana (J. jacana), which exhibit intense female-female competition for territories and mates and differ in the strength of sexual selection. We analyzed sex-biased dispersal by assessing genetic differentiation and individual assignment indices to determine the probability of an individual being a recent immigrant or philopatric in relation to its sampling location. Our findings reveal strong male-biased dispersal in Northern Jacanas, indicated by higher genetic structuring and philopatry in females. In contrast, Wattled Jacanas showed no significant dispersal bias between sexes. Furthermore, sexually selected traits in Northern Jacana females, such as larger body mass and wing spur length, were associated with philopatry, suggesting that larger females retain territories, whereas smaller females disperse. To our knowledge, this is the first genetic evidence of male-biased dispersal in a polyandrous species. Our findings reveal that sexually selected traits, in addition to territorial and mate competition, are important for understanding species and sex differences in dispersal evolution.

Keywords: Jacana; breeding dispersal; competitive phenotypes; mating competition; polyandry; population genetics; sex-biased dispersal.