The polyphagous shot-hole borer spread rapidly once introduced to California. The movement of the invasion front was more rapid than would be suggested by the dispersal kernel of other better-studied scolytine beetles. We scripted an agent-based model in R to understand the spread of this species and its impact on bird nesting habitat. We modeled the dispersal kernel as a negative exponential with the mean equal to the mean displacement reported in the literature for several scolytine species. The model played out upon a composite map of vegetation for California. The model was validated by matching the emergent spread rate of the modeled invasion front against the empirical spread rate calculated from actual survey results over seven years. Because the spread rate is likely dependent upon both the dispersal kernel and the propagule pressure, we ran parameter sweeps on these interacting parameters. We discuss how these two factors interact to determine the spread of the invasion front of this exotic invasive beetle.
.png)
