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. Extra-pair 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, multi-factor 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 extra-pair paternity in a socially monogamous bird, the black-throated blue warbler, Setophaga caerulescens. A male's probability of siring extra-pair young decreased with increasing distance to females, breeding density, and food availability. Males on food-poor territories were more likely to sire extra-pair young, and these offspring were produced further from the male's territory, relative to males on food-abundant territories. Moreover, males sired extra-pair 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 extra-pair 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预设，个体拥有均等的交配机会，且交配成功率的差异源于性性状的变异。然而，现有研究发现性性状无法解释雄性交配成功率的变异，这表明存在其他因素调控性选择的强度。额外配对父权（extra-pair paternity）在脊椎动物中极为普遍，可导致交配成功率产生变异，因此可作为阐释性选择运作机制的模型系统。本研究针对所有可能的雌-雄配对组合构建了空间显式多因子模型，以检验如下假说：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、繁殖间距以及配偶的巢期阶段）会影响个体获得额外配对父权的机会。雄性产生额外配对后代的概率，会随其与雌性的间距、繁殖密度及食物可获得性的升高而降低。相较于食物充足领地的雄性，食物匮乏领地的雄性更易产生额外配对后代，且此类后代的产生位置距离雄性领地更远。此外，雄性主要在其配偶的孵化期产生额外配对后代，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。