Environmental Variability and Thermal Acclimation in Neotropical and Temperate Zone Salamanders

Two neotropical and two temperate zone salamander species were acclimated at 12 or 22 C and their metabolic rates measured at 5, 15, and 25 C. Acclimation temperature altered standard metabolic rates of temperate zone salamanders but not neotropical salamanders. Also, acclimation temperature had a greater effect on several measures of postactivity oxygen consumption in the temperate zone species than in the neotropical species. However, acclimation temperature had little effect on anaerobic activity metabolism (lactate production) in either group. Fifteen species of temperate zone amphibians showed significant thermal acclimation of metabolism; the two neotropical salamanders were the only species that showed no acclimation. Relative stability of habitats may lead to loss of capacity for thermal acclimation in salamanders. Thermal acclimation in temperate zone salamanders and compensation for temperature in neotropical salamanders tend to moderate energetic costs. These mechanisms may allow normally cool salamanders to withstand energetic stresses often associated with high temperatures. However, lack of acclimation ability may restrict neotropical salamanders to smaller climatic ranges.