DISSERTATION RESEARCH: Separating Stochastic Events From Adaptive Evolution During A Biological Invasion

入侵物种是一个世界性的问题，但进化过程对可入侵性的影响程度却知之甚少。一个基本的问题是入侵过程是如何导致影响引进种群适应性的遗传变化的。由于基因变化既可以是偶然事件的结果，也可以是对自然选择的适应，这一事实使解决这个问题变得复杂。对于这两种不同的过程对入侵者成功的相对影响，人们知之甚少。这项拟议的研究研究了一种原产于欧洲的杂草植物，大约200年前被引入北美。分子工具将被用来揭示殖民期间的偶然事件是如何塑造遗传多样性的，并确定入侵者后裔的欧洲来源地区。来自同一祖先来源的欧洲和北美植物将在北美的两个实验花园里一起种植，以分析在控制潜在祖先后，适应性重要性状的差异是如何发生的。入侵物种的影响包括沉重的经济负担，每年给美国造成数十亿美元的损失。因此，这项研究的广泛影响将是促进对物种如何成为成功入侵者的理解，并有助于阐明一个重要应用问题的基础。

Invasive species are a worldwide problem, but the degree to which evolutionary processes influence invasibility is poorly understood. A fundamental question is how the process of invasion results in genetic changes that impact the fitness of introduced populations. Addressing this question is complicated by the fact that genetic changes can occur both as a consequence of chance events and by adaptation in response to natural selection. Little is known about the relative influence of these two distinct processes on the success of invaders. The proposed research studies a weedy plant native to Europe and introduced to North America about 200 years ago. Molecular tools will be employed to reveal how chance events during colonization shaped genetic diversity, and to identify the source areas in Europe from which invaders are descended. European and North American plants descended from the same ancestral sources will then be grown together in two experimental gardens within North America to analyze how divergence in adaptively important traits has occurred after controlling for underlying ancestry. The impact of invasive species includes a heavy economic burden, with yearly losses for the U.S. in the billions of dollars. Thus the broader impact of this study will be to advance the understanding of how species become successful invaders, and help illuminate the basis of an important applied problem.