Flexibility of metabolic rate to temperature coincides with diapause strategy

During dormancy, insects operate on a fixed energy budget and suppress metabolic rate to extend the duration that their energy reserves last. Extending energy stores to last an entire winter can pose a significant challenge, as some habitats have winters that last most of the year. There are cases where insects enter dormancy in mid-summer and remain until the following spring. This multi-season dormancy should pose an even more significant energetic challenge, since these insects must conserve energy during winter, as well as the warmest period of summer. We compared metabolic rate-temperature curves of two related species of pierid butterflies: Pieris napi, which is dormant through winter, and Anthocharis cardamines, which exhibits a multi-season dormancy. This comparison was conducted at several time points under 18°C and 2°C acclimation conditions. We found that A. cardamines can maintain considerable metabolic suppression when acclimated to high temperatures, which is only maintained until they are exposed to low temperatures. Overall P. napi exhibits much lower levels of metabolic plasticity. Metabolic suppression exhibited in A. cardamines is enough to prevent increased rates of mass loss at high temperatures. Together, this provides evidence that both environment and life history timing of dormancy can shape metabolic plasticity.