Data from: Ecological and social factors constrain spatial and temporal opportunities for mating in a migratory songbird

Many studies of sexual selection assume that individuals have equal mating opportunities and that differences in mating success result from variation in sexual traits. However, the inability of sexual traits to explain variation in male mating success suggests that other factors moderate the strength of sexual selection. Extrapair paternity is common in vertebrates and can contribute to variation in mating success and thus serves as a model for understanding the operation of sexual selection. We developed a spatially explicit, multifactor model of all possible female-male pairings to test the hypothesis that ecological (food availability) and social (breeding density, breeding distance, and the social mate’s nest stage) factors influence an individual’s opportunity for extrapair paternity in a socially monogamous bird, the black-throated blue warbler, Setophaga caerulescens. A male’s probability of siring extrapair young decreased with increasing distance to females, breeding density, and food availability. Males on food-poor territories were more likely to sire extrapair young, and these offspring were produced farther from the male’s territory relative to males on food-abundant territories. Moreover, males sired extrapair young mostly during their social mates’ incubation stage, especially males on food-abundant territories. This study demonstrates how ecological and social conditions constrain the spatial and temporal opportunities for extrapair paternity that affect variation in mating success and the strength of sexual selection in socially monogamous species.

诸多性选择相关研究均假定，个体拥有均等的交配机会，而交配成功率的差异由性特征的变异所导致。然而，性特征无法解释雄性交配成功率的变异，这表明存在其他因素可调控性选择的强度。额外配对父权（extrapair paternity）在脊椎动物中十分普遍，其可导致交配成功率出现变异，因此成为阐释性选择运作机制的研究模型。本研究构建了涵盖所有可能雌雄配对组合的空间显式多因素模型，以检验下述假说：在社会单配制鸟类黑喉蓝林莺（Setophaga caerulescens）中，生态因子（食物可获得性）与社会因子（繁殖密度、繁殖距离、配偶的巢期阶段）会影响个体获得额外配对父权的机遇。雄性育有额外配对后代的概率随其与雌性的距离、繁殖密度以及食物可获得性的提升而降低。栖息于食物匮乏领地的雄性更易育有额外配对后代，且相较于食物充足领地的雄性，这些后代的出生位置距其领地更远。此外，雄性育有额外配对后代的时段主要集中在其配偶的孵卵期，这一现象在食物充足领地的雄性中尤为显著。本研究阐明了生态与社会条件如何制约额外配对父权的空间与时间机遇，进而影响社会单配制物种的交配成功率变异与性选择强度。