In northern Canada, lake chub (Cyprinidae: Couesius plumbeus) have colonized a variety of thermal springs that differ substantially from the ancestral environment in both mean temperature and thermal variation. To examine whether this environmental change is associated with differences in physiological traits, we compared the thermal breadth, capacity for acclimation of thermal tolerance, and metabolic enzymes in populations of lake chub from three habitats: a warm but variable hot spring, a thermally constant warm spring, and a seasonally variable temperate lake. Thermal breadth was generally lowest in fish from the constant environment, and this difference was statistically significant in fish acclimated at 10° and 25°C. Critical [...]
