The risk of mapping risk: Effect of selection on the lower lethal temperature and geographical range predictions of light brown apple moth (Epiphyas postvittana)

Forecasting future distributions of invasive insects is an important component of many management and regulatory decisions.  However, numerous challenges exist in creating accurate, biologically relevant models and maps that are meaningful over time. In particular, no models currently account for the potential of a species to adapt to a new environment.  For much of North America, adaptation to cold temperature is especially important; cold is often a driving factor preventing many insects from surviving year round.  For example, cold is likely to constrain the future distribution of the Light Brown Apple Moth (LBAM; Epiphyas postvittana), a recent insect invader to North America. As a highly polyphagous pest of many agricultural, horticultural, and forest plants, LBAM could have significant economic and ecological impacts.

In this study, we sought to incorporate the cold adaptation potential of LBAM into a simplified ecological niche model to more accurately project where cold temperature may prevent this species from surviving in the future.  We measured the effect of short-term cold exposure on survival of late instar larvae (the overwintering stage) before and after several generations of artificial selection. We then estimated the temperatures before and after selection needed to cause 50% mortality (LT₅₀).  Finally, we identified the proportion of the last 10 years in which temperatures in North America were equal to or colder than these lethal temperatures. Our study showed an increased survival to low temperature following selection, and highlights the importance of considering adaptation potential when predicting the future distributions of invasive insects.