Data from: Male age mediates reproductive investment and response to paternity assurance

Theory predicts that male response to reduced paternity will depend on male state and interactions between the sexes. If there is little chance of reproducing again, then males should invest heavily in current offspring, regardless of their share in paternity. We tested this by manipulating male age and paternity assurance in the burying beetle Nicrophorus vespilloides. We found older males invested more in both mating effort and parental effort than younger males. Furthermore, male age, a component of male state, mediated male response to perceived paternity. Older males provided more prenatal care, whereas younger males provided less prenatal care, when perceived paternity was low. Adjustments in male care, however, did not influence selection acting indirectly on parents, through offspring performance. This is because females adjusted their care in response to the age of their partner, providing less care when paired with older males than younger males. As a result offspring, performance did not differ between treatments. Our study shows, for the first time, that a male state variable is an important modifier of paternity–parental care trade-offs and highlights the importance of social interactions between males and females during care in determining male response to perceived paternity.

理论预测，雄性对父权水平降低的响应将取决于雄性自身状态以及两性间的相互作用。若雄性再次繁殖的概率极低，则无论其当前的父本份额如何，都应加大对当前后代的投入。我们通过操控斑埋葬甲（Nicrophorus vespilloides）的雄性年龄与父权保障程度来验证这一假说。研究发现，相较于年轻雄性，年长雄性在交配投入与亲本投入上均更为丰厚。此外，作为雄性状态的组成部分，雄性年龄会调控雄性对感知到的父权水平的响应：当感知父权水平较低时，年长雄性会提供更多产前抚育，而年轻雄性的产前抚育则相对较少。不过，雄性抚育行为的调整并未通过后代表现对亲本产生间接的选择压力。这是因为雌性会根据配偶的年龄调整抚育投入——与年长雄性配对时，雌性的抚育投入相较于与年轻雄性配对时更少。因此，不同处理组间的后代表现并无显著差异。本研究首次证实，雄性状态变量是调控父本份额-亲本抚育权衡的关键因子，并凸显了抚育过程中两性间的社会互动，在决定雄性对感知父权水平的响应时所发挥的重要作用。