INVESTIGATING THE INFLUENCE OF EXPANSION LOAD AND TRADE-OFFS ON THE RANGE EXPANSION OF A BIOLOGICAL CONTROL AGENT OF A RANGELAND WEED

My long-term goal is to improve our ability to predict and manage range expansions of pests and biological control agents through understanding the roles of genetic load and trade-offs between fecundity and dispersal in the range expansion ofa biological control agent for an invasive weed. Increased frequency of deleterious mutations that reduce fitness (increased genetic load) can slow range expansion, while increased dispersal can speed range expansion. These contrasting processes can be linked through theory on life history trade-offs, which predicts negative correlations between dispersal and reproduction. Understanding factors that drive the range expansions of invasive pests and their biological control agents is key to effective long-term management. I focus onDiorhabda carinulata, a biological control agent of the rangeland and riparian weed, tamarisk. The project objectives are to 1)measure genetic load in the D. carinulata range expansion and evaluate whether environmental gradients or purging have reduced or eliminated expansion load and to 2)Evaluate trade-offs between dispersal and reproduction at the core and edge of the D. carinulata range expansion within the context of expansion load.