Data from: Asynchronous hatching in the burying beetle, Nicrophorus quadripunctatus, maxmises parental fitness

Life history theory predicts that natural selection favours parents who balance investment across offspring to maximize fitness. Theoretical studies have shown that the optimal level of parental investment from the offspring's perspective exceeds that of its parents, and the disparity between the two generates evolutionary conflict for the allocation of parental investment. In various species, the offspring hatch asynchronously. The age hierarchy of the offspring usually establishes competitive asymmetries within the brood and determines the allocation of parental investment among offspring. However, it is not clear whether the allocation of parental investment determined by hatching pattern is optimal for parent or offspring. Here, we manipulated the hatching pattern of the burying beetle Nicrophorus quadripunctatus to demonstrate the influence of hatching pattern on the allocation of parental investment. We found that the total weight of a brood was largest in the group that mimicked the natural hatching pattern, with the offspring skewed towards early hatchers. This increases parental fitness. However, hatching patterns with more later hatchers had heavier individual offspring weights, which increases offspring fitness, but this hatching pattern is not observed in the wild. Thus, our study suggests that the natural hatching pattern optimizes parental fitness, rather than offspring fitness.

生活史理论（Life history theory）预测，自然选择会青睐那些在子代间均衡分配亲本投资以最大化自身适合度的亲本。已有理论研究表明，从子代视角出发的最优亲本投资水平高于亲本自身的最优投资水平，二者的差异会引发亲本资源分配层面的进化冲突。诸多物种的子代均存在异步孵化现象，子代的年龄层级通常会在一窝幼体间形成竞争不对称性，并决定亲本在子代间的资源分配模式。然而，由孵化模式决定的亲本资源分配，究竟对亲本还是子代更为最优，目前尚无定论。本研究以埋葬甲（Nicrophorus quadripunctatus）为实验对象，通过操控其孵化模式，探究孵化模式对亲本资源分配的影响。我们发现，模拟自然孵化模式（即子代群体偏向早孵化个体）的实验组，其整窝幼体总重量最大，该结果可提升亲本适合度。但在子代更多为晚孵化个体的孵化模式下，单只子代的体重更高，这可提升子代适合度，然而这类孵化模式在野生环境中并未被观测到。综上，本研究表明自然孵化模式优化的是亲本适合度，而非子代适合度。