Evolutionary Genomics of Populus trichocarpa (Western Poplar)

Forest trees are an important pool of biodiversity at the gene, individual and an ecosystem level. This variation is a result of complex environmental interactions, as well as neutral and selective forces acting on populations. Patterns of standing genetic variation are the result of adaption to past and contemporary climate change, but also historical demographic events, and disentangling the role of these forces is a central problem in population genomics. The overall goal of this study is to characterize the relative effects of demography and selection in the genome of Populus trichocarpa, a riparian deciduous tree species of North America. Specifically, I used a variety of methods to summarize patterns of genetic diversity and population structure in P. trichocarpa, and to reconstruct its demographic history. I subsequently incorporated these demographic insights to guide the application of several methods to identify genome-wide targets of natural selection within and among rangewide populations adapted to heterogeneous selection regimes. Results of this study provide insights into the history of divergence and differentiation in P. trichocarpa populations and help us identify the functional genetic variants contributing to phenotypic divergence and fitness of the individuals in it.