Biology "Life at the Edge: Ecological Genomics of Climate Adaptation in Range-Edge Populations of Balsam Poplar"

Dr. Stephen Keller is assistant professor of plant biology at the University of Vermont.

"In light of past and ongoing climate warming, understanding the genetics of local adaptation to climate has become an important research focus in plant ecological genomics. In long-lived species such as forest trees, populations located along southern range edges may be particularly vulnerable to climate warming if they exist at their current physiological limits of environmental stress, and may also face increased exposure to introgression from co-occurring species where ranges overlap. Additionally, southern range edge populations may harbor unique adaptive variants that have been selected under the earliest-onset and longest growing seasons in the species’ range. To address these issues, my lab has been investigating how landscape-scale climate variability has shaped adaptive genomic diversity across the geographic range of Populus balsamifera (balsam poplar), a widespread forest tree and a model system for studying local adaptation to climate. Our approaches integrate measurement of functional traits in common garden experiments, genome-wide patterns of single nucleotide polymorphisms (SNPs) from high-throughput sequencing, and targeted genotyping of the Populus flowering time network-- genes that function as key regulators of dormancy onset and release in response to seasonality. We use these data to determine the adaptive relationships between phenotype, genotype and climate, and model how climatic variability and the potential for introgressive hybridization in different parts of the range have shaped adaptive diversity. Our results yield novel insights into the landscape patterns of local adaptation in core and southern edge populations, and have implications for plant conservation and forest management under climate change."