What factors govern the rate of spread of an invasive species? Assessing the importance of dispersal and selection in range expansion

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In this project, mathematical modeling and genetic analysis are combined with experiments and field surveys to better predict the spread of the invasive hemlock woolly adelgid, Adelges tsugae (HWA), across the eastern United States. This forest pest kills eastern hemlock trees and has caused both economic and ecological damage. Genetic markers will be used to identify distinct HWA clonal lines that will each have its spread rate, population growth rate, and cold tolerance measured. This information will be used in combination with survey data reporting the genetic structure of the invasive populations to develop a mathematical model examining the role of dispersal and selection for surviving cold winter conditions in driving the range expansion of HWA.This research will substantially increase the understanding of how invasive species spread across landscapes. Hemlocks have both economic and cultural importance, and their loss concerns groups ranging from forestry officials to local citizens. Understanding how and why HWA spreads throughout the landscape will allow the identification of locations most at risk for infestation for targeted control efforts. This work also increases the ability of scientists and resource managers to anticipate the movement of geographic range boundaries in response to the changing climatic regimes likely to occur as a consequence of global warming.