Data from: Neighbouring-group composition and within-group relatedness drive extra-group paternity rate in the European badger (Meles meles)

Extra-group paternity (EGP) occurs commonly among group-living mammals and plays an important role in mating systems and the dynamics of sexual selection; however, socio-ecological and genetic correlates of EGP have been underexplored. We use 23 years of demographic and genetic data from a high-density European badger (Meles meles) population, to investigate the relationship between the rate of EGP in litters and mate availability, mate incompatibility and mate quality (heterozygosity). Relatedness between within-group assigned mothers and candidate fathers had a negative quadratic effect on EGP, whereas the number of neighbouring-group candidate fathers had a linear positive effect. We detected no effect of mean or maximum heterozygosity of within-group candidate fathers on EGP. Consequently, EGP was associated primarily with mate availability, subject to within-group genetic effects, potentially to mitigate mate incompatibility and inbreeding. In badgers, cryptic female choice, facilitated by superfecundation, superfoetation and delayed implantation, prevents males from monopolizing within-group females. This resonates with a meta-analysis in group-living mammals, which proposed that higher rates of EGP occur when within-group males cannot monopolize within-group females. In contrast to the positive meta-analytic association, however, we found that EGP associated negatively with the number of within-group assigned mothers and the number of within-group candidate fathers; potentially a strategy to counter within-group males committing infanticide. The relationship between the rate of EGP and socio-ecological or genetic factors can therefore be intricate, and the potential for cryptic female choice must be accounted for in comparative studies.群外父权 (Extra-group paternity, EGP) 在群居哺乳动物中普遍存在，对交配系统及性选择动态具有重要作用；然而目前针对EGP的社会生态与遗传关联研究仍有待深入探索。本研究依托高密度欧洲獾（Meles meles）种群长达23年的种群统计与遗传数据，探究了产仔群中EGP发生率与配偶可获得性、配偶不相容性以及配偶质量（即杂合度，heterozygosity）之间的关联。组内已确定母兽与候选父兽之间的亲缘关系对EGP存在负二次效应，而邻近种群候选父兽的数量则呈现线性正效应。未发现组内候选父兽的平均或最大杂合度对EGP存在显著影响。因此，EGP主要与配偶可获得性相关，且受组内遗传效应的调控，这一关联可能用于缓解配偶不相容与近交问题。在欧洲獾中，借助超受精 (superfecundation)、同期复孕 (superfoetation) 与延迟着床 (delayed implantation) 机制实现的隐秘雌性选择 (cryptic female choice)，可阻止雄性独占组内雌性个体。这一结果与群居哺乳动物的一项元分析结论相契合，该分析指出当组内雄性无法独占组内雌性时，EGP发生率会更高。然而与元分析得出的正相关关联不同，本研究发现EGP与组内已确定母兽数量、组内候选父兽数量呈负相关；这可能是一种对抗组内雄性杀婴行为的策略。因此，EGP发生率与社会生态或遗传因素之间的关联可能极为复杂，比较研究中必须纳入隐秘雌性选择的潜在影响。