Dissertation Research: Late Quaternary History of Balsam Poplar in North America

覆盖今天俄罗斯东北部大部分地区和阿拉斯加的广阔地区在末次冰期最大期仍然没有冰。 这个冰河时期的避难所，被称为Beringia，对北方树木和灌木的作用在很大程度上是未知的。 北方木本植物类群的流行假设有利于在遥远的北方灭绝，随后从大陆冰盖南部的避难所灭绝。 这一长期存在的观点最近受到了来自阿拉斯加的化石树花粉的挑战，这些花粉可以追溯到第四纪晚期，这表明香脂杨或白杨是白令岛内冰川事件的幸存者。 本研究的目的是评估这一替代假说的分子植物地理学和植物区系地理学的互补领域的证据，这项研究的影响延伸到理解白令考古学，白令对北极和寒带植物的物种和种群多样性的影响，以及过去的气候变化的影响。 此外，本研究将记录的遗传多样性的地理分布在香脂白杨提供了一个关键的资源知识基础，为未来的发展，具有重要经济意义的白杨杂交种。 预计白杨将在农林复合经营、CO2生物封存计划以及生物燃料和生物柴油生产中发挥关键作用。 最终，这项研究将有助于发展基线假设，了解过去的人口统计学事件对白杨基因组变异的影响。

A vast area covering much of present-day north-eastern Russia and Alaska remained ice-free through the last glacial maximum. The role of this ice age refugium, referred to as Beringia, for boreal trees and shrubs is largely unknown. The prevailing hypothesis for boreal woody plant taxa favors extinction in the far north, with subsequent recolonization from a refugium south of continental ice sheets. This long-standing view was challenged recently by discovery of fossil tree pollen from Alaska dating to the late-Quaternary which indicated balsam poplar, or Populus balsamifera, is a candidate for survival of glaciation events within Beringia. This research aims to assess this alternative hypothesis by drawing upon evidence from the complementary fields of molecular phylogeography and floristic plant geography.The implications of this research extend to understanding Beringian archeology, the impact of Beringia on species and population diversity of arctic and boreal plants, and the influences of past climate change. Moreover, this study will document the geographic distribution of genetic diversity within balsam poplar providing a key resource knowledge-base for future development of economically important poplar hybrids. Poplar is predicted to play a key role in agroforesty, CO2 biosequestration programs and biofuel and biodiesel production. Ultimately, this research will aid in development of baseline hypotheses for understanding the influences of past demographic events on genomic variation in poplar.