Meeting Abstract
Due to harsh environmental conditions and limited food availability, overwintering organisms are dependent on a store of energy reserves that consists mostly of lipids to sustain them until spring. To compensate for this limitation, metabolic activity of overwintering individuals is characteristically low. Winter warming poses potential threats to overwintering organisms as metabolic activity is expected to increase due to increases in biochemical reaction rates, which may cause organisms to deplete their energy stores more quickly. To better understand the effects of winter warming on metabolic activity, we used stop-flow respirometry to measure resting metabolic rate after winter warming exposures in diapausing Pieris rapae pupae. We report that warmed individuals had a higher respiratory quotient (i.e., the ratio of carbon dioxide produced to oxygen consumed) than did control individuals, indicating that they switched from using lipid reserves to other reserves such as carbohydrates and/or proteins during recovery from heat stress. We also measured metabolic rates in real time during exposure to winter warming conditions to characterize thermal reaction norms across a range of temperatures. As predicted, metabolic activity increased with increasing temperature. Because metabolic rates increased and pupae switched to metabolizing energy resources (i.e., carbohydrates and proteins) that are likely to be more limited and, our results indicate that winter warming may cause diapausing pupae to deplete energy reserves. This research provides insight into the physiological consequences of winter warming on diapausing insect species and how these organisms may respond as environmental temperatures continue to increase during the winter months.
