COS 133-2 - Effect of temperature acclimation period to high temperatures on upper thermal tolerance in a terrestrial salamander

Abstract: Physiological traits such as the critical thermal maximum (CT_max) can be important for understanding the vulnerability of species to climate and habitat change. According to some studies, CT_max is a somewhat plastic trait that can vary at least in part with thermal conditions, suggesting the possibility of short-term acclimation to changing thermal environments. Thermal acclimation capacity is defined as the physiological adjustment of organisms to temperature variation, which can affect phenotypic traits such as CT_max. Indeed, the relation between acclimation capacity and CT_max has been widely studied in ectotherms like fish, amphibians, and reptiles, and it is generally observed that CT_max increases when the acclimation temperature is higher. However, there is a lack of information about whether amphibians respond differently to long- and short-term acclimation. Understanding thermal acclimation capacity in response to rapid environmental change is of great importance, because it may reduce vulnerability, especially to habitat modification occurring in a short period. Here, we evaluate the thermal acclimation capacity in the Eastern Red-backed salamander, Plethodon cinereus, in response to short- and long-term acclimation. We exposed salamanders to three different treatments: a control group maintained at 15°C for 30 days; a short acclimation period with exposure to 15°C for 28 days and 23°C for 48 hours, and long-term acclimation at 23°C for 30 days. We measured body condition (mass/snout-vent length) to avoid bias before and after the treatments. After treatments, we measured the CT_max, measuring body temperature after individuals experienced the loss of righting response. CT_max was unrelated to body condition across all treatments (F_1,55=2.62, P=0.11). Although CT_max was highest in the group that experienced long-term acclimation to warm temperatures, our results were not statistically significant (F_2,54=2.36, P=0.10). Our results suggest that Plethodon cinereus could show seasonal acclimation, rather than short-term acclimation to sudden warm temperatures. To conclude, our results provide limited evidence that there may be a degree of acclimation capacity (or phenotypic plasticity) in CTmax in Plethodon cinereus, but that different acclimation periods did not affect the degree of plasticity. We encourage the continuation of this line of research on rapid acclimatization effects and their ecological implications in the face of novel temperature patterns arising from human-induced environmental change.