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

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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.