Dissertation Research: Patterns of Past and Present Selection on Mating System Traits in Collinsia verna

随着进化论的教学在美国各地的学校系统中受到挑战，对生物学家来说，记录自然选择在单个种群中随着时间的推移而产生变化的案例是很重要的。同样重要的是，将过去的选择与观察到的物种内部和物种之间的多样性模式联系起来。几项研究表明，自然选择在单个种群中会随着时间的推移而发生变化。例如，我们知道加拉帕戈斯雀按种子大小选择喙大小会导致喙大小随着时间的推移而发生变化。然而，很少有研究人员将过去的选择与现在的多样性联系起来。个体群体之间的多样性可以通过两种方式产生：1)通过在单独的群体中选择有利于不同类型的特征，以及2)通过在单独的群体中随着时间的推移而随机改变。这项研究试图在一个单一的植物物种--蓝眼睛玛丽身上，解开这两个导致多样性的原因。蓝眼睛玛丽的种群通过自花授粉产生种子的能力各不相同，这一功能即使在昆虫传粉者稀少的情况下也能确保种子生产。研究人员将检验这一假设，即不同种群的自交能力不同，是因为种群已经适应了栖息地传粉者丰度的差异，而不是因为种群的随机分化。此外，他们将检验这样一个假设，即最优的自交率目前在不同的种群中是不同的。这项研究将有助于我们理解自然选择如何创造和维持多样性模式，以及过去的选择如何与现在的选择相关。

As the teaching of evolution is being challenged in school systems across the United States, it is important for biologists to document cases where natural selection is producing change over time in a single population. It is also essential to connect selection in the past to observed patterns of diversity within and among species. Several studies have shown that natural selection produces change over time in a single population. For example, we know that selection on the beak size of Galapagos finches by seed size has resulted in changes in beak size over time. However, few researchers have linked past selection to present diversity. Diversity among groups of individuals can arise in two ways: 1) by selection favoring different types of characters in separate populations, and 2) by random change in separated populations over time. This study seeks to disentangle these two causes of diversity within a single plant species, Blue-eyed Mary. Populations of Blue-eyed Mary vary in their ability to produce seeds through self-pollination, a function that insures seed production even when insect pollinators are rare. The researchers will test the hypothesis that selfing ability varies across populations because populations have adapted to differences in pollinator abundance in their habitats, and not because the populations have differentiated randomly. Further, they will test the hypothesis that the optimum selfing rate currently varies across populations. This study will contribute to our understanding of how natural selection creates and maintains patterns of diversity, and how selection in the past can be related to selection in the present.