Data from: Paternal care and litter size coevolution in mammals

Biparental care of offspring occurs in diverse mammalian genera, and is particularly common among species with socially monogamous mating systems. Despite numerous well-documented examples however, the evolutionary causes and consequences of paternal care in mammals are not well understood. Here we investigate the evolution of paternal care in relation to offspring production. Using comparative analyses to test for evidence of evolutionary associations between male care and life history traits, we explore if biparental care is likely to have evolved because of the importance of male care to offspring survival, or if evolutionary increases in offspring production are likely to result from the evolution of biparental care. Overall, we find no evidence that paternal care has evolved in response to benefits of supporting females to rear particularly costly large offspring or litters. Rather, our findings suggest that increases in offspring production are more likely to follow the evolution of paternal care, specifically where males contribute depreciable investment such as provisioning young. Through coevolution with litter size, we conclude that paternal care in mammals is likely to play an important role in stabilising monogamous mating systems and could ultimately promote the evolution of complex social behaviours.

双亲抚育（biparental care）后代的现象广泛存在于多样的哺乳动物类群，在实行社会一夫一妻制婚配体系的物种中尤为常见。尽管已有诸多详实记载的案例，但哺乳动物父育（paternal care）行为的进化成因与演化后果仍未得到充分阐释。本研究围绕后代产出与父育行为的演化展开探究。我们借助比较分析方法，检验雄性抚育与生活史性状间的演化关联，以此探讨双亲抚育的演化究竟是因雄性抚育对后代存活的关键作用而产生，还是后代产出的进化提升更可能由双亲抚育的演化所催生。总体而言，我们未发现证据支持父育行为的演化是为了通过协助雌性抚育代价高昂的大型后代或幼崽窝次以获取收益。反之，我们的研究结果表明，后代产出的提升更可能紧随父育行为的演化而来——尤其当雄性能够提供可折旧的抚育投入（如为幼崽提供食物补给）时。通过与幼崽窝次规模的协同演化分析，我们推断哺乳动物的父育行为可能在稳定一夫一妻制婚配体系中发挥重要作用，并最终可能促进复杂社会行为的演化。