Data from: Sexual conflict and antagonistic coevolution across water strider populations

Microevolutionary studies have demonstrated sexually antagonistic selection on sexual traits, and existing evidence supports a macroevolutionary pattern of sexually antagonistic coevolution. Two current questions are how antagonistic selection within populations scales to divergence among populations, and to what extent intraspecific divergence matches species-level patterns. To address these questions, we conducted an intraspecific comparative study of sexual armaments and mating behaviours in a water strider (Gerris incognitus) in which male genitals grasp resistant females and female abdominal structures help ward off males. The degree of exaggeration of these armaments coevolves across species. We found a similar strong pattern of antagonistic coevolution among populations, suggesting that sexual conflict drives population differentiation in morphology. Furthermore, relative exaggeration in armaments was closely related to mating outcomes in a common environment. Interestingly, the effect of armaments on mating was mediated by population sexual size dimorphism. When females had a large size advantage, mating activity was low and independent of armaments, but when males had a relative size advantage, mating activity depended on which sex had relatively exaggerated armaments. Thus, a strong signal of sexually antagonistic coevolution is apparent even among populations. These results open opportunities to understand links between sexual arms races, ecological variation and reproductive isolation.微进化研究（microevolutionary studies）已证实性拮抗选择（sexually antagonistic selection）作用于性征，现有研究证据亦支持性拮抗协同进化（sexually antagonistic coevolution）的宏观演化模式（macroevolutionary pattern）。当前亟待解答的两个核心问题为：种群内部的拮抗选择如何推演至种群间的演化分化，以及种内分化（intraspecific divergence）在多大程度上契合物种水平模式（species-level patterns）。为解答上述问题，我们针对一种水黾——隐黾蝽（Gerris incognitus）——开展了性武器（sexual armaments）与交配行为（mating behaviours）的种内比较研究（intraspecific comparative study）；该物种种群中，雄性生殖器（male genitals）可抓握抗拒交配的雌性个体，雌性腹部结构（female abdominal structures）则用于抵御雄性的求偶行为。跨物种层面，这类性武器的夸张程度呈现协同演化特征。本研究在种群间亦发现了类似的强性拮抗协同演化模式，表明性冲突（sexual conflict）推动了形态学（morphology）层面的种群分化（population differentiation）。此外，性武器的相对夸张程度与共同环境（common environment）下的交配结果（mating outcomes）显著相关。值得注意的是，性武器对交配过程的影响受种群性大小二态性（sexual size dimorphism）介导：当雌性具备体型优势（size advantage）时，交配活动（mating activity）水平较低且与性武器的夸张程度无关；而当雄性具备相对体型优势时，交配活动则取决于哪一性别的性武器更为夸张。综上，即便在种群层面，性拮抗协同演化的显著信号依然清晰可辨。本研究结果为解析性军备竞赛（sexual arms races）、生态变异（ecological variation）与生殖隔离（reproductive isolation）之间的关联提供了新的研究契机。