Contribution of males to brood care can compensate for their food consumption from a shared resource

The sharing of the same food source among parents and offspring can be a driver of the evolution of family life and parental care. However, if all family members desire the same meal, competitive situations can arise, especially if resource depletion is likely. When food is shared for reproduction and the raising of offspring, parents have to decide whether they should invest in self-maintenance or in their offspring and it is not entirely clear how these two strategies are balanced. In the burying beetle Nicrophorus vespilloides, parents care for their offspring either bi- or uniparentally at a vertebrate carcass as the sole food source. The question of whether biparental care in this species offers the offspring a better environment for development compared with uniparental care has been the subject of some debate. We tested the hypothesis that male contribution to biparental brood care has a beneficial effect on offspring fitness but that this effect can be masked because the male also feeds from the shared resource. We show that a mouse carcass prepared by two Nicrophorus beetles is lighter compared with a carcass prepared by a single female beetle at the start of larval hatching and provisioning. This difference in carcass mass can influence offspring fitness when food availability is limited, supporting our hypothesis. Our results provide new insights into the possible evolutionary pathway of biparental care in this species of burying beetles.

亲代与子代共享同一食物源，可推动家庭生活与双亲抚育行为的演化。然而，若所有家庭成员的食物需求一致，则可能引发竞争态势，尤其当资源耗竭风险较高时。当为繁殖与抚育后代而共享食物时，亲代需权衡自身维持与子代抚育的能量投入策略，目前学界尚未完全明确这两种策略的平衡机制。在埋葬甲（Nicrophorus vespilloides）中，亲代可通过双亲抚育或单亲抚育的方式，以脊椎动物尸体作为唯一食物源来照料子代。相较于单亲抚育，该物种的双亲抚育能否为子代提供更优的发育环境，这一问题此前已引发诸多学术讨论。本研究验证了如下假说：雄性对双亲育幼抚育的贡献可对子代适合度产生有益影响，但由于雄性同样会取食共享的资源，这一有益效应可能被掩盖。我们发现，在幼虫孵化与育幼投喂初期，由两只埋葬甲共同处置的小鼠尸体重量，要轻于仅由单只雌虫处置的尸体。在食物可获得性受限的情况下，尸体重量的这一差异可影响子代适合度，从而验证了我们的假说。本研究结果为该种埋葬甲双亲抚育行为的潜在演化路径提供了全新的学术视角。