Effects of temperature on the development of two ambrosia beetle species frequently moved via international trade

Recent detections of ambrosia beetles (Curculionidae: Scolytinae) at ports of entry around the globe highlight continued risks associated with the movement of wood-packaging materials (WPM) used in international trade. To invade new regions via international shipping, insects need to survive transit, but the climatic conditions experienced along shipping routes can also shape insect development and phenology. Inside WPM in a shipping container, for example, changes in temperature can affect invasion success by determining the timing between developmental events (e.g., adult emergence) and the landfall and/or opening of the shipping container. To that end, we reared two species of frequently-intercepted ambrosia beetles, Xylosandrus crassiusculus (Motschulsky) and Anisandrus maiche Kurentzov, under four temperature conditions to characterize developmental rate, including degree-days required to complete each life stage. We then linked our findings with reconstructed climatic conditions along selected international shipping routes to simulate patterns of arrival. Our results provide a framework for assessing seasonal changes in invasion risk.