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

气候驱动的分布向更高纬度的转变预计将发生在许多树种身上。一个物种的迁徙能力将主要取决于其活动范围向两极边缘的种群的个体的扩散和殖民，这些迁徙过程的细节可能决定未来数千年新种群的遗传结构，从而决定它们适应新环境的能力。这项研究试图通过考察过去冰川消退后向北迁徙的情况，以及美国东部温带落叶林的一种优势树种--美洲山毛榉--的遗传种群结构，来预测这一未来。通过分析保存在密歇根州北部数千年湖泊沉积物中的花粉和大型化石的遗传数据，该项目将阐明通过山毛榉模式进行殖民的重要模式，并展示这些模式是如何导致遗传多样性模式的。通过进一步将这些历史数据与今天对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的迁徙的长期遗传后果。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，因为我们依赖森林提供许多产品，依赖多样性维持良好的环境。该项目还将通过帮助提出哪些种群处于遗传风险并需要立即保护关注，来为森林保护和管理做出贡献。此外，该项目还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.