Understanding the Causes of Geographic Variation in Sex Ratio of a Gynodioecious Plant

进化生物学家长期以来一直对了解生物种群如何变得彼此不同感兴趣，因为这是物种形成的必要前提。种群性别比的变化（例如雌性对雄性的数量，或雌性对雌雄同体的数量）为研究种群分化机制提供了一个很好的模型。因为种群性别比决定了个体的身份和可用配偶的数量，它影响了种群内部和种群之间基因变异的分布。这个项目将调查为什么在小种群和温暖的地方，开花植物（半边莲）的雌性和雌雄同体的比例更高。我们将测试女性频率的变化是否由于自然选择，或者是否其他进化力量，如遗传漂变和基因流动，正在阻止许多种群达到平衡的性别比例。区分这些不同进化机制的影响是很重要的，因为它们产生了不同的群体遗传结构模式。这项研究将为评估繁殖系统如何影响物种改变其活动范围以应对气候变化，特别是全球变暖的能力提供一个框架。如果由于自然选择，雌性水蛭属植物在年平均气温较高的地区更常见，那么全球变暖应该会使种群更加偏向于雌性，这可能会影响迁移速度和物种持久性。

Evolutionary biologists have long been interested in understanding how populations of organisms become different from one another, because it is a necessary precursor to speciation. Variation in population sex ratio (for example, the number of females vs. males, or females vs. hermaphrodites) provides an excellent model for investigating mechanisms of population differentiation. Because the population sex ratio determines the identity and number of available mates, it affects how genetic variation is distributed within and between populations. This project will investigate why the proportion of females vs. hermaphrodites in a flowering plant (Lobelia siphilitica) are higher in small populations and at warmer sites. We will test whether female frequencies vary because of natural selection, or if other evolutionary forces, such as genetic drift and gene flow, are preventing many populations from reaching an equilibrium sex ratio. Distinguishing the effects of these different evolutionary mechanisms is important because they produce distinct patterns of population genetic structure.This research will provide a framework for evaluating how breeding systems influence the ability of species to modify their range in response to climate change, particularly global warming. If female L. siphilitica plants are more common in areas with higher annual mean temperatures because of natural selection, then populations should become more female-biased in response to global warming, which could affect migration rates and species persistence.