Meeting Abstract
Ectotherms require external heat from their environment to maintain their bodies in optimal temperature ranges. During winter, many terrestrial ectotherms respond physiologically by shifting their temperature tolerance ranges and increasing cold resistance. Most studies investigating plasticity of physiological variables look for the presence and direction of change, but very few investigate the rate of change. To examine the rate of cold responses, we simulated winter conditions for two non-native populations of the Italian Wall Lizard Podarcis siculus. In accordance with the climatic variability hypothesis, we predicted that animals from the more variable environment (Hempstead, New York) would have faster rates of acclimation to a cold environment compared to animals from a relatively stable environment (San Pedro, California). Animals were housed at 29°C for a year before beginning a cold acclimation treatment at 13°C. Whole body physiological variables (standard metabolic rate, evaporative water loss, thermal preference, and thermal tolerance) were measured prior to the acclimation treatment. Histological variables (serum osmolality, hematocrit, and hemoglobin concentration) were also measured before cold acclimation. Cold tolerance was then tested weekly during acclimation until no further change was observed. At this point, post-acclimation whole body physiological and histological variables were measured. This study defines the rate of change in cold tolerance under physiologically relevant conditions. Incorporating rate of change of commonly measured variables in thermal biology will help us better understand physiological responses to climatic shifts and invasion of novel environments.
