Data from: Receptive females mitigate costs of sexual conflict

Males typically gain fitness from multiple mating, whereas females often lose fitness from numerous mating, potentially leading to sexual conflict over mating. This conflict is expected to favor the evolution of female resistance to mating. However, females may incur male harassment if they refuse to copulate; thus, greater female resistance may increase costs imposed by males. Here, I show that the evolution of resistance to mating raises fitness disadvantages of interacting with males when mating is harmful in female adzuki bean beetles, Callosobruchus chinensis. Females that were artificially selected for higher and lower remating propensity evolved to accept and resist remating, respectively. Compared with females that evolved to accept remating, females that evolved to resist it suffered higher fitness costs from continuous exposure to males. The costs of a single mating measured by the effect on longevity did not differ among selection line females. This study indicates that receptive rather than resistant females mitigate the fitness loss resulting from sexual conflict, suggesting that even though mating is harmful, females can evolve to accept additional mating.

雄性通常可通过多次交配提升自身适合度（fitness），而雌性往往因频繁交配损失适合度，这一现象可能引发交配层面的性冲突（sexual conflict）。此类冲突理论上会推动雌性演化出交配抵抗能力。然而，若雌性拒绝交配，便可能遭受雄性的骚扰；因此，更强的雌性交配抵抗能力或许会加剧雄性施加的适配成本。本文发现，在交配行为对雌性有害的赤豆象（Callosobruchus chinensis）中，交配抵抗能力的演化会提升雌性与雄性互动时的适合度劣势。研究人员通过人工选育高、低再交配倾向（remating propensity）的雌性个体，分别获得了演化出接受再交配与抵抗再交配表型的品系。相较于演化出接受再交配表型的雌性品系，演化出抵抗再交配表型的雌性在持续接触雄性时，会承受更高的适合度成本。以寿命变化为指标衡量的单次交配成本，在各选育品系的雌性间并无显著差异。本研究表明，相较于具备交配抵抗能力的雌性，接受交配的雌性可缓解性冲突带来的适合度损失，这一结果暗示即便交配对雌性存在危害，雌性仍可演化出接受额外交配的适应性策略。