Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
PLoS One. 2014 Feb 25;9(2):e90207. doi: 10.1371/journal.pone.0090207. eCollection 2014.
The prevalence of sexual conflict in nature, as well as the supposedly arbitrary direction of the resulting coevolutionary trajectories, suggests that it may be an important driver of phenotypic divergence even in a constant environment. However, natural selection has long been central to the operation of sexual conflict within populations and may therefore constrain or otherwise direct divergence among populations. Ecological context may therefore matter with respect to the diversification of traits involved in sexual conflict, and if natural selection is sufficiently strong, such traits may evolve in correlation with environment, generating a pattern of ecologically-dependent parallel evolution. In this study we assess among-population divergence both within and between environments for several traits involved in sexual conflict. Using eight replicate populations of Drosophila melanogaster from a long-term evolution experiment, we measured remating rates and subsequent offspring production of females when housed with two separate males in sequence. We found no evidence of any variation in male reproductive traits (offense or defense). However, the propensity of females to remate diverged significantly among the eight populations with no evidence of any environmental effect, consistent with sexual conflict promoting diversification even in the absence of ecological differences. On the other hand, females adapted to one environment (ethanol) tended to produce a higher proportion of offspring sired by their first mate as compared to those adapted to the other (cadmium) environment, suggesting ecologically-based divergence of this conflict phenotype. Because we find evidence for both stochastic population divergence operating outside of an ecological context and environment-dependent divergence of traits under sexual conflict, the interaction of these two processes is an important topic for future work.
性冲突在自然界中的普遍性，以及由此产生的共同进化轨迹的所谓任意方向，表明即使在恒定的环境中，它也可能是表型分歧的重要驱动因素。然而，自然选择长期以来一直是种群内性冲突的核心，因此可能会限制或指导种群之间的分歧。因此，生态背景可能与涉及性冲突的特征的多样化有关，如果自然选择足够强大，这些特征可能会与环境相关进化，产生与生态相关的平行进化模式。在这项研究中，我们评估了涉及性冲突的几个特征的种群内和种群间在不同环境中的分化。使用来自长期进化实验的 8 个重复的黑腹果蝇种群，我们测量了雌性在与两个不同雄性连续交配时的再次交配率和随后的后代产量。我们没有发现任何雄性生殖特征（攻击或防御）的变化证据。然而，雌性再次交配的倾向在八个种群中存在显著差异，没有任何环境影响的证据，这与即使在没有生态差异的情况下，性冲突也能促进多样化的观点一致。另一方面，适应一种环境（乙醇）的雌性与适应另一种环境（镉）的雌性相比，其后代中由第一任配偶所生育的比例更高，这表明这种冲突表型存在基于生态的分歧。因为我们发现了两种过程的证据，一种是在没有生态背景的情况下随机种群分歧，另一种是性冲突下特征的环境依赖性分歧，所以这两个过程的相互作用是未来工作的一个重要课题。
