Data from: Flexible parents: joint effects of handicapping and brood size manipulation on female parental care in Nicrophorus vespilloides

Parental care is highly variable, reflecting that parents make flexible decisions in response to variation in the cost of care to themselves and the benefit to their offspring. Much of the evidence that parents respond to such variation derives from handicapping and brood size manipulations, the separate effects of which are well understood. However, little is known about their joint effects. Here we fill this gap by conducting a joint handicapping and brood size manipulation in the burying beetle Nicrophorus vespilloides. We handicapped half of the females by attaching a lead weight to their pronotum, leaving the remaining females as controls. We also manipulated brood size by providing each female with 5, 20 or 40 larvae. In contrast to what we predicted, handicapped females spent more time provisioning food than controls. We also found that handicapped females spent more time consuming carrion. Furthermore, handicapped females spent a similar amount of time consuming carrion regardless of brood size, while controls spent more time consuming carrion as brood increased. Females spent more time provisioning food towards larger broods, and females were more likely to engage in carrion consumption when caring for larger brood. We conclude that females respond to both handicapping and brood size manipulations, but these responses are largely independent of each other. Overall, our results suggest that handicapping might lead to a higher investment into current reproduction, and that it might be associated with compensatory responses that negate the detrimental impact of higher cost of care in handicapped parents.

亲代抚育（parental care）具有高度的种内变异性，这源于亲代会根据自身抚育成本与子代获益的动态变化，做出灵活的抚育决策。目前支持亲代响应此类变化的大量证据，均来自亲代表重操控（handicapping）与窝仔数（brood size）操控的相关实验，且学界已明确这两种操控各自的独立效应。但目前对二者的联合效应仍知之甚少。本研究以埋葬甲Nicrophorus vespilloides为实验对象，通过联合开展亲代表重操控与窝仔数操控，填补了这一研究空白。我们通过在半数雌性个体的前胸背板（pronotum）上附着铅坠以实施负重操控，剩余雌性个体作为空白对照组。同时，我们通过为每头雌性提供5、20或40头幼虫来调控窝仔数。与实验预期相悖的是，负重操控组雌性的食物投喂时长显著长于对照组。我们还发现，负重组雌性的腐肉（carrion）取食时长同样更长。进一步分析显示，负重组雌性的腐肉取食时长不受窝仔数变化的影响，而对照组雌性的腐肉取食时长则随窝仔数增加而显著延长。雌性个体对更大窝仔的食物投喂时长更长，且在抚育大窝仔群时更倾向于进行腐肉取食。综上，我们认为雌性亲代会同时响应负重操控与窝仔数操控，但这两类响应基本相互独立。总体而言，本研究结果表明，亲代表重操控可能会促使亲代提升当前繁殖投入，且可能伴随补偿性响应，以抵消负重亲代抚育成本升高所带来的不利影响。