Meeting Abstract
To conserve energy during winter many insects enter diapause, a dormant state in which metabolic rate is suppressed. Metabolic suppression is gradually reversed during diapause termination. Thermal conditions experienced during winter impact the degree of metabolic suppression through phenotypic plasticity. In winter, snow modifies the thermal environment by acting as an insulator that buffers from cold and variable air temperatures. The stable, constant temperatures experienced under snow may impact the degree of metabolic suppression, and the time course over which suppression is released during diapause termination. Incorporating winter metabolic plasticity in energetic models will allow us to more accurately predict how climate change will impact winter energy stress. Populations of the willow leaf beetle Chrysomela aeneicollis in the Sierra Nevada Mountains overwinter as adults for up to eight months of their one-year life cycle. In these environments there is highly variable interannual snowfall, which can lead to dramatically different thermal environments. Beetles were collected from the wild and overwintered under simulated stable below-snow conditions and variable exposed conditions in the laboratory. We quantified temperature-metabolic rate curves monthly from February to May through the transition of diapause to post-diapause quiescence. We found that beetles had similar thermal sensitivity and metabolic suppression regardless of winter thermal environment. As beetles transitioned out of diapause, there was no shift in thermal sensitivity, but a steady decrease in general suppression. This implies that our current models are underestimating winter energy use and that late winter warm bouts will pose greater energetic challenges for overwintering insects.
