1st Place: Think of the children! Female host preference and offspring performance of mountain pine beetle in lodgepole and jack pines

Mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) can attack and reproduce in as many as 17 different pine species with variable success. In mixed species stands, MPB does not attack all species equally and shows a preference for some species over others. Due to climate change mediated range expansion, MPB is encountering the new host species jack pine which is evolutionarily naïve to MPB attack. If more susceptible naïve hosts provide an advantage for offspring, they could be preferred if MPB are given the option to host switch. Host preference could also be based on natal host experience and MPB will prefer the host species that they grew up in and may not host switch despite the potential advantage. As females are the colonizing sex, we tested female MPB preference for lodgepole and jack pines using walking olfactometer bioassays and quantified the time beetles spent in proximity to volatiles from lodgepole and jack pine phloem. In performance experiments we introduced MPB pairs to cut logs of either the same or opposite species as their natal host and measured parental success and offspring performance by measuring body size and lipid content. Parents that developed in and subsequently reproduced in lodgepole pine had offspring with significantly better condition suggesting a cost to switching to jack pine. Understanding how MPB performs during a host switch and which species it prefers will aid in predicting spread potential and the behaviour of MPB at the interface of lodgepole and jack pine.