A mechanistic understanding of the response of metabolic rate to temperature is essential for understanding thermal ecology and metabolic adaptation. Although the Arrhenius equation has been used to describe the effects of temperature on reaction rates and metabolic traits, it does not adequately describe two aspects of the thermal performance curve (TPC) for metabolic rate—that metabolic rate is a unimodal function of temperature often with maximal values in the biologically relevant temperature range and that activation energies are temperature dependent. We show that the temperature dependence of metabolic rate in ectotherms is well described by an enzyme‐assisted Arrhenius (EAAR) model that accounts for the temperature‐dependent contribution of enzymes to decreasing the activation energy required for reactions to occur. The model is mechanistically derived using the thermodynamic rules that govern protein stability. We contrast our model with other unimodal functions that also can be used to describe the temperature dependence of metabolic rate to show how the EAAR model provides an important advance over previous work. We fit the EAAR model to metabolic rate data for a variety of taxa to demonstrate the model's utility in describing metabolic rate TPCs while revealing significant differences in thermodynamic properties across species and acclimation temperatures. Our model advances our ability to understand the metabolic and ecological consequences of increases in the mean and variance of temperature associated with global climate change. In addition, the model suggests avenues by which organisms can acclimate and adapt to changing thermal environments. Furthermore, the parameters in the EAAR model generate links between organismal level performance and underlying molecular processes that can be tested for in future work.

No abstract

Summary 1.Habitat loss is a leading cause of global amphibian declines. Forest removal is a particularly significant threat because an estimated 82% of amphibians rely on forests for part of their lives. 2. Biphasic amphibians rely on suitable terrestrial habitat to support their post-metamorphic growth and survival and also to maintain appropriate habitat and landscape connectivity. 3. We created 4 replicate, 16-ha experimental arrays in the southeastern USA to examine the effects of forest removal on migratory movements of adult biphasic amphibians. Each array contained four forest-harvesting treatments that included an unharvested control, a partially harvested stand, a clearcut with coarse woody debris retained, and a clearcut with coarse woody debris removed. 4. Some amphibian species emigrated from wetlands in significantly greater numbers through forest controls compared with harvested treatments. Also, salamanders were generally more sensitive to forest removal than were frogs, with a significantly greater proportion of salamanders migrating through forested habitat compared to frogs. 5. For several species, individuals were significantly more likely to avoid clearcuts when emigrating compared to immigrating. Individuals that emigrated into clearcut treatments were more likely to reverse direction and return to wetlands in some species. 6. Synthesis and applications . Our study identifies one mechanism by which forest removal shapes the abundance and distribution of amphibians in terrestrial habitat. To promote the persistence of amphibian populations, conservation efforts should focus on preserving forest habitat adjacent to reproduction sites. Such measures are especially important where forest habitat connects local populations or where it links reproduction sites to other habitat features necessary for amphibian growth, survival, or overwintering.