Sexual conflict coevolution - population size, divergence and the emergence of new variation

选择在生物多样性产生中的作用是一个令人兴奋和有争议的话题。人们早就认识到，适应新环境可以导致新形式的进化，但最近人们对性选择，特别是性冲突推动快速进化的潜力产生了极大的兴趣。该理论认为，雄性在不断的压力下进化出新的方式来操纵他们的配偶，这样他们就可以在特定雄性的后代身上投资更多，而不是他们过去或未来的配偶。反过来，雌性也会受到强有力的选择，以重新控制自己的繁殖，并优化自己的繁殖成功率，而不是配偶的。有一些种内军备竞赛的证据，但性冲突在多大程度上可以驱动快速进化和人口分化的关键问题仍然研究不足，几个关键问题仍然几乎完全被忽视，特别是：1。在性冲突驱动的进化过程中，种群规模对促进或延缓进化有多重要？2.小群体之间的分化更快，是因为通过遗传漂变的等位基因随机丢失很重要，还是在大群体中，因为有更多的突变输入和更多的长期遗传变异？3.突变输入是否会导致种群在适应率上的变化，或者站立变异的水平是否总是更重要？这些问题对于试图理解变异的起源和维持的生物学家来说是非常有趣的。它们还对保护和圈养繁殖方案的设计产生影响，在这些方案中，较大的种群饲养成本更高，但可能保留更多的遗传变异，并经历更高的总体突变输入。研究对抗性共同进化的一个主要问题是，反适应往往掩盖了推动其进化的适应。例如，一种新的雄性精液化学物质可以加速产卵，只有通过观察雄性对其伴侣的影响才能确定。然而，一旦雌性进化出对雄性化学物质缺乏敏感性，就不再可能检测到适应或反适应。在这个建议中，我们使用一种新的方法来揭示这种变化：我们利用一个种群的甲虫Callosobruchus maculatus，自然有大量的性冲突驱动的适应和反适应。我们的研究从我们在强制一夫一妻制（女性和男性只允许一个配偶）条件下保持了7年（90多代）的种群开始。这些一夫一妻制的种群将失去许多冲突适应能力和大部分遗传多样性。我们将通过创造一系列允许自然交配制度的新种群，包括男性和女性之间的利益冲突，重新引入性选择和性冲突。这些实验群体将包括在总体群体大小和初始水平的常设遗传变异方面不同的重复。我们将检查人口在间隔跨越新的冲突人口与基线一夫一妻制人口，以揭示新的适应冲突和重新建立的冲突特征，已减少到低频率的一夫一妻制线的选择性优势的消除。30代后，我们将进行种群之间的杂交，以直接测量在我们的研究期间进化的生殖隔离程度，以及种群规模和遗传多样性对这一过程的影响。我们的研究将揭示性冲突如何快速推动进化，这如何转化为种群之间的分歧（物种形成的燃料）以及种群规模和遗传变异性对对抗性共同进化速率的影响。

The role of selection in the generation of biodiversity is an exciting and controversial topic. It has long been recognised that adaptation to new environments can lead to the evolution of new forms, but recently there has been great interest in the potential for sexual selection and in particular sexual conflict to drive rapid evolution. The theory is that males are under constant pressure to evolve new ways to manipulate their mates so that they invest more in the offspring of that particular male rather than any of their past or future mates. Females in turn are under strong selection to regain control over their reproduction and optimise their own reproductive success rather than that of their mate's. There is some evidence for intraspecific arms-races but the key question of the extent to which sexual conflict can drive rapid evolution and population divergence remains poorly studied and several key issues remain almost completely neglected, particularly: 1. How important is population size in promoting or retarding evolution driven by sexual conflict? 2. Is divergence faster between small populations because random loss of alleles through genetic drift is important, or in large populations because there is greater mutational input and more standing genetic variation? 3. Can mutational input cause populations to vary in the rate of adaptation or is the level of standing variation always more important? These questions are of great interest to biologists attempting to understand the genesis and maintenance of variation. They also have implications for the design of conservation and captive breeding programmes where larger populations are more expensive to rear, but may retain more genetic variation and experience higher overall mutational inputs. A major problem in studying antagonistic coevolution, is that counter-adaptations often mask the adaptations which have driven their evolution. For instance a new male seminal chemical that accelerates egg laying might only be identified by observing the effects of males on their partners. However, once females evolve lack of sensitivity to the male chemical, it no longer becomes possible to detect either the adaptation or the counter-adaptation. In this proposal we use a novel approach to reveal such variation: we utilise a population of beetles Callosobruchus maculatus that naturally have substantial sexual conflict driven adaptations and counter-adaptations. Our study begins with populations that we have been keeping for over 7 years (90+ generations) under conditions of enforced monogamy (females and males only allowed a single mate). These monogamy populations will have lost many of their conflict adaptations and much of their genetic diversity. We will re-introduce sexual selection and sexual conflict to this system by creating a range of new populations where the natural mating regime is allowed, including conflicts of interest between males and females. These experimental populations will include replicates that differ in overall population size, and initial levels of standing genetic variation. We will examine populations at intervals crossing the new conflict populations with the baseline monogamy population to reveal new adaptations to conflict and the re-establishment of conflict traits that have been reduced to low frequencies by the removal of their selective advantages in the monogamy lines. After 30 generations we will conduct crosses between populations to gain direct measures of the degree of reproductive isolation that has evolved during our study and the influence that population size and genetic diversity has had on this process. Our study will reveal how rapidly sexual conflict can drive evolution, how this can translate into divergence between populations (the fuel for speciation) and the influences of population size and genetic variability on the rate of antagonistic coevolution.