Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada.
Evolution. 2012 Feb;66(2):544-57. doi: 10.1111/j.1558-5646.2011.01464.x. Epub 2011 Oct 5.
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 behaviors 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.
微观进化研究表明，性特征存在性拮抗选择，现有证据支持性拮抗协同进化的宏观进化模式。目前存在两个问题，即种群内的拮抗选择如何与种群间的分歧相适应，以及种内分歧在多大程度上与物种水平的模式相匹配。为了解决这些问题，我们对一种水生步甲（Gerris incognitus）的性武器和交配行为进行了种内比较研究，在这种水生步甲中，雄性生殖器抓住有抵抗力的雌性，而雌性腹部结构有助于抵御雄性。这些武器的夸张程度在物种间共同进化。我们发现，种群之间存在着类似的强烈的拮抗协同进化模式，这表明性冲突驱动了形态的种群分化。此外，在共同环境中，武器的相对夸张程度与交配结果密切相关。有趣的是，武器对交配的影响受到种群性体型二态性的调节。当雌性具有较大的体型优势时，交配活动较低且不依赖于武器，但当雄性具有相对体型优势时，交配活动取决于哪一性别具有相对夸张的武器。因此，即使在种群之间，也明显存在着强烈的性拮抗协同进化信号。这些结果为理解性军备竞赛、生态变异和生殖隔离之间的联系提供了机会。
