Data from: Sexual conflict and intrasexual polymorphism promote assortative mating and halts population differentiation

Sexual conflict is thought to be an important evolutionary force in driving phenotypic diversification, population divergence and speciation. However, empirical evidence is inconsistent with the generality of sexual conflict as enhancing population divergence. Here we demonstrate an alternative evolutionary outcome in which sexual conflict plays a conservative role in maintaining male and female polymorphisms locally, rather than promoting population divergence. In diving beetles, female polymorphisms have evolved in response to male mating harassment and sexual conflict. We present the first empirical evidence that this female polymorphism is associated with 1) two distinct and sympatric male morphological mating clusters (morphs) and 2) assortative mating between male and female morphs. Changes in mating traits in one sex led to a predictable change in the other sex which leads to predictable within-population evolutionary dynamics in male and female morph frequencies. Our results reveal that sexual conflict can lead to assortative mating between male offence and female defense traits, if a stable male and mating polymorphisms is maintained. Stable male and female mating polymorphism are an alternative outcome to accelerating coevolutionary arms race driven by sexual conflict. Such stable polymorphisms challenge the common view of sexual conflict as an engine of rapid speciation via exaggerated co-evolution between sexes.性冲突（Sexual conflict）被视为推动表型多样化（phenotypic diversification）、种群分化（population divergence）与物种形成（speciation）的关键进化驱动力。然而，现有实证证据并不支持性冲突普遍促进种群分化这一主流论断。本研究揭示了一类别样的进化结局：性冲突在本地维持雌雄两性多态性（polymorphisms）时发挥保守作用，而非推动种群分化。在潜水甲虫（Diving beetles）中，雌性多态性的演化是对雄性求偶骚扰与性冲突的适应性响应。本研究首次提供相关实证证据，表明这类雌性多态性与两大特征相关：其一为两种同域分布（sympatric）、形态迥异的雄性交配形态集群（即雄虫形态型）；其二为雌雄形态型间的选型交配（assortative mating）。某一性别的交配性状发生改变，可预测地引发另一性别的对应变化，进而使种群内雌雄形态型的频率呈现可预测的进化动态。本研究结果显示，若能维持稳定的雌雄交配多态性，性冲突可催生雄性进攻性状与雌性防御性状之间的选型交配。稳定的雌雄交配多态性，是性冲突驱动的协同进化军备竞赛（coevolutionary arms race）加速升级之外的另一类进化结局。此类稳定多态性，挑战了“性冲突是通过两性间夸张的协同进化推动快速物种形成的核心引擎”这一主流学术观点。