Plasticity drives extreme cold tolerance of emerald ash borer (Agrilus planipennis) during a polar vortex

Invasive species must often survive combinations of environmental conditions that differ considerably from their native range; however, for a given species it is unclear whether improved tolerance is the result of phenotypic plasticity or genetic adaptation (or both). Agrilus planipennis (Coleoptera: Buprestidae; the emerald ash borer) is an invasive pest of Fraxinus trees in North America and Europe. Previous studies in southwestern Ontario, Canada, showed that A. planipennis is freeze avoidant, preventing internal ice formation by accumulating molar concentrations of glycerol in its hemolymph and depressing its supercooling point (SCP, the temperature at which it freezes). The cold tolerance of these southwestern Ontario animals was used to predict potential distribution, revealing that some Canadian cities should be too cold to allow populations to persist. However, a small population of A. planipennis has persisted in Winnipeg, Manitoba, Canada, through several severe ‘polar vortex’...