Meeting Abstract
Many temperate ectotherms use thermal acclimation to remain functional over a wide range of body temperatures, but few studies have investigated if populations of a single species have evolved differences in thermal plasticity. Therefore, we asked if thermal plasticity has diverged between northern and southern populations of the eastern newt (Notophthalmus viridescens). Eastern newts from Florida and Maine were acclimated to cold (6°C) or warm (28°C) conditions for 12 weeks. Following acclimation, we compared the thermal plasticity of locomotor performance (burst swimming speed) and the activity of metabolic enzymes between populations. The thermal plasticity of locomotor performance differed between populations–the newts from Maine were better able to acclimate to low temperature compared to the Florida newts. The activities of metabolic enzymes in liver and skeletal muscle also responded to thermal acclimation differently between populations. We also compared the thermal plasticity of membrane composition between populations. Cold acclimation resulted in a lower saturated fatty acid (SFA) content in cold compared to warm-acclimated newts from Florida, but acclimation did not affect SFA content in liver membranes of the Maine population. In liver, cold acclimation resulted in a higher monounsaturated fatty acid (MUFA) content in the Florida population and a higher polyunsaturated fatty acid (PUFA) content in the Maine population. These results suggest that the plasticity of membrane composition differs between northern and southern populations. Together, these studies demonstrate that the thermal plasticity of ectotherms is labile and can diverge among different populations of a single species.
