Sexual selection, conflict and isolation: experimental insight into the population genetic consequences of mate competition and the origin of species

在大多数有性繁殖的物种中，雄性为获得配偶和/或使配子受精而竞争。这种竞争是持久的、广泛的，而且往往是激烈的，它产生了生殖成功的差异，从而导致了性选择。配偶竞争也是男性和女性选择不同的一个关键原因，由此产生的性冲突可能导致对男性有利但对女性有害的特征的进化。奢侈的性展示（如孔雀的尾巴）和夸张的性竞争武器（如雄鹿的鹿角）的进化，都是配偶竞争的结果；这些特征的进化是因为它们增加了雄性相对于其他雄性的性适应性。然而，通过对性选择、性冲突和交配模式的影响，配偶竞争还有其他进化后果，虽然人们对这些后果知之甚少，但却可以说是基本的。我的研究试图更全面地理解这些，集中在配偶竞争的进化后果：1)非性适应性，通过它对适应新环境和清除有害突变的影响；Ii)性别偏倚的基因表达，这是广泛的两性二态性的基础，也是生物多样性的主要组成部分；性隔离，这是种群间基因流动的障碍，对新物种的起源很重要。在实验室和野外对果蝇和其他昆虫进行研究时，我们结合了行为和适合度分析，我们很大程度上依赖于实验进化的力量，使我们能够比较在不同交配竞争制度下复制种群的进化过程如何展开。我们特别关注交配环境的生态学，研究它是如何改变交配竞争的进化结果的，以及果蝇研究中极不寻常的实验室环境——研究这一主题的模型系统——是否会影响我们的观点。我们对生态改变配偶竞争的潜在机制及其对适应和净化的影响提供了可操作的测试。我们还量化了性别偏见基因表达如何在配偶竞争操纵和发生这种情况的环境中进化，以及配偶竞争及其生态如何影响物种形成。160多年前，达尔文提出，由于性选择倾向于最健康、最有活力的雄性，配偶竞争的更广泛进化结果是增强了适应性。事实证明，这过于简单化了；配偶竞争具有复杂的环境依赖效应，具有多种种群遗传后果，包括但不限于适应。这项工作对我们理解基本的进化过程以及生态如何塑造它们具有广泛的意义。

In most sexually reproducing species, males compete for access to mates and/or to fertilize their gametes. Such competition is persistent, widespread, and often intense, and it generates the variation in reproductive success that causes sexual selection. Mate competition is also a key reason why selection differs between males and females, and the resulting sexual conflict can lead to the evolution of traits that benefit males but harm females as a by-product. The evolution of extravagant sexual displays, like the peacock's tail, and exaggerated weapons of sexual rivalry, like a buck's antlers, are well-understood consequences of mate competition; such traits evolve because they increase a male's sexual fitness relative to other males. However, through its effects on sexual selection, sexual conflict, and patterns of mating, mate competition has other evolutionary consequences that are poorly understood, yet arguably fundamental. My research seeks a more comprehensive understanding of these, focussing on the evolutionary consequences of mate competition for: i) nonsexual fitness, via its effects on adaptation to novel environments and the purging of harmful mutations; ii) sex-biased gene expression, which underlies the extensive sexual dimorphism and that constitutes a major component of biological diversity; and iii) sexual isolation, a barrier to gene flow between populations that is important to the origin of new species. Working with fruit flies (Drosophila) and other insects, in both the lab and the field, we use a combination of behavioural and fitness assays, and we rely heavily on the power of experimental evolution, enabling us to compare how the evolutionary process unfolds in replicate populations under different mate competition regimes. We give particular attention to the ecology of the mating environment, studying how it alters the evolutionary consequences of mate competition and whether the highly unusual lab environment of Drosophila studies -a model system for work on this topic- may have biased our perspective. We provide manipulative tests of the underlying mechanisms by which ecology alters mate competition and the effects this has on adaptation and purging. We also quantify how sex-biased gene expression evolves in response to manipulations of mate competition and the environment in which this occurs, and how mate competition and its ecology affect speciation. Over 160 years ago, Darwin suggested that, because sexual selection favours the healthiest and most vigorous males, the broader evolutionary consequence of mate competition is increased adaptation. This, it turns out, was too simplistic; mate competition can have complex and environment-dependent effects with a variety of population genetic consequence that include, but are not limited to, adaptation. This work has broad implications for our understanding of fundamental evolutionary processes and how ecology shapes them.