1 Department of Biology, Freshwater Biology, University of Copenhagen , Copenhagen 2100 , Denmark.
2 Center for Biodiversity Outcomes, Arizona State University , Tempe, AZ , USA.
Proc Biol Sci. 2019 Mar 27;286(1899):20190251. doi: 10.1098/rspb.2019.0251.
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 that sexual conflict enhances 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 (i) two distinct and sympatric male morphological mating clusters (morphs) and (ii) 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 defence traits, if a stable male and female mating polymorphisms are maintained. Stable male and female mating polymorphisms are an alternative outcome to an 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 coevolution between sexes.
性冲突被认为是推动表型多样化、种群分化和物种形成的重要进化力量。然而，经验证据并不一致，即性冲突增强了种群分化。在这里，我们展示了一个替代的进化结果，其中性冲突在局部维持雄性和雌性多态性方面发挥保守作用，而不是促进种群分化。在潜水甲虫中，雌性多态性已经进化以应对雄性交配骚扰和性冲突。我们首次提供了经验证据表明，这种雌性多态性与（i）两种截然不同的、同域的雄性形态交配聚类（形态）和（ii）雄性和雌性形态之间的交配选择有关。一性的交配特征的变化导致另一性的可预测变化，从而导致雄性和雌性形态频率的可预测的种群内进化动态。我们的研究结果表明，如果稳定的雄性和雌性交配多态性得以维持，性冲突可能导致雄性攻击和雌性防御特征之间的交配选择。稳定的雄性和雌性交配多态性是由性冲突驱动的加速协同进化军备竞赛的替代结果。这种稳定的多态性挑战了性冲突作为通过两性之间夸张的协同进化快速形成物种的引擎的常见观点。
