The threat of global climate change makes it critical to understand how changing patterns of temperature variability influence individual organism performance and species interactions. According to the Metabolic Theory of Ecology (MTE), rates of biological processes at varying scales are fundamentally limited by organism metabolic rates. Metabolism has in turn been found to scale predictably with temperature according to the Boltzmann-Arrhenius model for enzyme kinetics, which can be adapted to account for enzyme deactivation at high temperatures using the Sharpe-Schoolfield model. An important outstanding question is how key metabolic parameters are influenced by plastic organism responses such as thermal acclimation. In this study, we investigated how thermal acclimation influences metabolic performance for four species of adult frogs (Pseudacris crucifer, P. triseriata, Lithobates clamitans, and Osteopilus septentrionalis) by using their rate of observable respiratory movements as a proxy for metabolic rate. We held each frog at one of three “acclimation temperatures” for two weeks then transferred each frog to one of a range of “performance temperatures” at which we recorded frog respiratory rates. We then estimated key metabolic parameters to determine whether and how thermal acclimation influenced the temperature dependence of frog respiratory performance.
Results/Conclusions:
All species’ respiration rates increased with temperature; however, thermal acclimation effects on breathing rate varied by species. Thermal acclimation had no effect on respiration rates of P. triseriata or O. septentrionalis. Respiration rate increased with acclimation temperature in L. clamitans; however, this effect was only present immediately after the temperature shift. Respiration rate also evidently increased with acclimation temperature in P. crucifer. However, P. cucifer mass significantly decreased with increasing acclimation temperature, which might have influenced this result.
We also estimated activation energies for respiration rate in each species by fitting a Sharpe-Schoolfield model to each dataset. Activation energy estimates for respiration rate of each frog species ranged from approximately 0.2 to 0.4. Our estimated activation energies are less than 0.65, the estimated average activation energy for metabolism predicted by MTE. This study provides valuable baseline data for generating MTE-based thermal models for these frog species.