Data from: Transgenerational effects of maternal sexual interactions in seed beetles

Mating bears large costs to females, especially in species with high levels of sexual conflict over mating rates. Given the direct costs to females associated with multiple mating, which include reductions in lifespan and lifetime reproductive success, past research focused on identifying potential indirect benefits (through increases in offspring fitness) that females may accrue. Far less attention has been given to understanding how costs of sexual interactions to females may span across generations. Hence, little is known about the transgenerational implications of variation in mating rates, and net consequences of maternal sexual activities across generations. Using the seed beetle, Callosobruchus maculatus, a model system for the study of sexual conflict, we look at the effects of mating with multiple males versus a single male, and tease apart effects due to sexual harassment and those due to mating per se, over three generations. We show that across generations, harassed females suffer a severe decline in fitness compared to non-harassed females, while multiply mated females showed no difference in net fitness compared to singly mated females. Overall, it appears that the transgenerational benefits of multiple mating counteract but do not exceed the direct costs of harassment. Our study highlights the importance of examining transgenerational effects from an inclusive (looking at both indirect benefits but also costs) perspective, and the need to investigate transgenerational effects across several generations if we are to fully understand the consequences of sexual interactions, sexual conflict evolution, and the interplay of sexual conflict and multi-generational costs and benefits.交配行为会给雌性个体带来高昂代价，尤其是在交配率相关性冲突（sexual conflict）程度较高的物种中。鉴于多雄交配会给雌性带来直接代价，包括寿命缩短与终生繁殖成功率下降，过往研究多聚焦于探寻雌性可能获得的潜在间接收益——即通过提升后代适合度（offspring fitness）实现的收益。但针对雌性性互动代价如何跨代传递的研究却极为匮乏。因此，学界对交配率变异的跨代影响，以及雌性性活动的跨代净效应仍知之甚少。本研究以性冲突研究的模式生物（model system）——绿豆象（Callosobruchus maculatus）为实验对象，在三代实验周期内，对比了多雄交配与单雄交配对雌性的影响，并拆解区分了性骚扰（sexual harassment）与交配行为本身各自带来的效应。实验结果显示，跨代尺度下，遭受性骚扰的雌性适合度较未受骚扰雌性出现严重下降；而多雄交配雌性的净适合度与单雄交配雌性并无差异。总体而言，多雄交配的跨代收益能够抵消性骚扰带来的直接代价，但无法超越该代价。本研究强调，需以包容性视角——同时兼顾间接收益与代价——来探究跨代效应；若要全面理解性互动的后果、性冲突的演化规律，以及性冲突与跨代成本收益间的相互作用，则必须开展多世代的跨代效应研究。