DISSERTATION RESEARCH: Historical dynamics of American beech at its northern range limit

在气候驱动下，许多树种的分布将向高纬度地区转移。一个物种迁移的能力将主要取决于其范围的两极边缘种群的个体的分散和殖民化，这些迁移过程的细节可能决定未来几千年新种群的遗传结构，从而决定它们适应新环境的能力。本研究试图通过考察冰川消退后过去向北迁移的情况，以及美国东部温带落叶林中一种主要树木美国山毛榉目前的遗传种群结构，来预测这一未来。通过分析保存在上密歇根州湖泊沉积物中数千年的花粉和大型化石的遗传数据，该项目将阐明山毛榉模式殖民的重要模式，并展示这些模式如何导致遗传多样性的模式。通过进一步将这些历史数据与当今山毛榉种群的遗传分析相结合，该项目将有助于了解气候驱动迁移的长期遗传后果。了解气候变化将如何影响森林和生物多样性对社会很重要，因为我们的许多产品都依赖森林，而维持良好运行的环境又依赖森林的多样性。该项目还将有助于森林的保护和管理，帮助指出哪些种群在遗传上有危险，需要立即予以保护。此外，该项目将在科研过程中培养本科生。

Climate-driven shifts in distribution towards higher latitudes are expected to occur for many tree species. The ability of a species to move will depend mostly upon dispersal and colonization by individuals from populations at the poleward edge of its range, and the details of these migration processes are likely to determine the genetic structure of the new populations for millennia to come, and hence their ability to adapt to their new environment. This research seeks to anticipate this future by examining the past northward migration after glacial retreat and the present genetic population structure of a dominant tree of the temperate deciduous forests of the eastern U.S., American beech. By analyzing genetic data from pollen and macrofossils preserved in lake sediments for thousands of years in Upper Michigan, the project will elucidate the important patterns of colonization by beech patterns and show how these led to patterns of genetic diversity. By further integrating these historical data with genetic analyses of beech populations today, the project will help understand the long-term genetic consequences of climate-driven migration. Understanding how climate change will affect forests and biological diversity is important to society, because we depend upon forests for many products and upon diversity for maintaining a well-functioning environment. The project will also contribute to forest conservation and management by helping suggest which populations are genetically at risk and need immediate conservation attention. Moreover, the project will train undergraduate students in the process of scientific research.