Data from: Are females in good condition better able to cope with costly males?

The costs of mating for a female might depend on both her phenotype and that of her mate. Sexually antagonistic male traits that negatively affect females are often condition-dependent, so a male’s rearing environment can affect the costs he imposes on his mate. Likewise, a female’s ability to resist male-imposed costs might be condition-dependent. We experimentally manipulated female and male body condition in the seed beetle Callosobruchus maculatus by rearing larvae on a good or poor quality diet. We then tested whether the cost of mating for a female (measured as copulation behaviors associated with sexual conflict as well as her fecundity and survival) depended on her and/or her mate’s body condition. As expected, females in better condition laid more eggs and lived longer, indicating higher fitness. More interestingly, females that mated with males in better condition had shorter copulations and started to kick sooner. Both results are potentially indicative of greater sexual conflict. We suggest that these changes in mating behavior might be driven by the higher toxicity of ejaculates of males that are in better condition. Crucially, however, the lack of any interaction between male and female condition for the variables measured suggests that any increase in the costs of mating with a male in better condition is not ameliorated by the female’s own condition.

雌性的交配代价可能同时取决于自身的表型（phenotype）及其配偶的表型。对雌性产生负面影响的性拮抗雄性性状（sexually antagonistic male traits）通常具有条件依赖性（condition-dependent），因此雄性的饲养环境会影响其对配偶施加的交配代价。同理，雌性抵御雄性施加的交配代价的能力也可能具有条件依赖性（condition-dependent）。本研究以绿豆象（Callosobruchus maculatus）为实验对象，通过让幼虫取食优质或劣质饲料，人为操控雌雄个体的身体状态（body condition）。随后我们检验了雌性的交配代价——以与性冲突（sexual conflict）相关的交配行为、雌性的繁殖力及存活率作为衡量指标——是否取决于自身及/或配偶的身体状态。如预期一致，身体状态更佳的雌性产卵量更多、寿命更长，这意味着其适合度（fitness）更高。更值得关注的是，与身体状态更佳的雄性交配的雌性，其交配时长更短，且更早开始踢击雄性。这两项结果均有可能预示着更强的性冲突程度。我们推测，交配行为的这类变化可能由身体状态更佳的雄性的射精液（ejaculates）毒性更强所驱动。然而关键的是，所检测的变量均未显示雌雄身体状态间存在交互效应，这表明：与身体状态更佳的雄性交配所带来的交配代价提升，并不会因雌性自身的身体状态而得到缓解。