Thermophysiology in liolaemids from Patagonia: Has evolution written comparative stories in Gondwanian lands?

IBARGÜENGOYTÍA N. R.; MEDINA S. M.; FERNANDEZ, JIMENA BEATRIZ; SCOLARO A.

San Carlos de Bariloche

Simposio; VI Southern Connection Congress; 2010

Natural selection should favor a co-evolution of traits strongly related to fitness, and for ectotherms, of prime importance should be behaviors that influence the effectiveness of thermoregulation (E) and hence, the body temperature (Tb). In cold temperate climates, reptile life histories have adapted to prolonged periods of resource scarcity, producing a variety of similar evolutionary paths resulting in convergence among different lineages. We compare the Tb and operative temperatures in the field, preferred Tb from the laboratory (Tp), and E values of liolaemids from Patagonia, Argentina, to that of reptiles from similar latitudes elsewhere in the Southern Hemisphere. At high latitudes, the liolaemids show significant limitations in thermoregulation; they are poor thermoregulators or constrained thermoconformers and they show the lowest Tb for the genus (23-26ºC). The Tp, a very conservative character in liolaemids, are significantly higher (32-34ºC) than the environmental temperatures in Patagonia; they are not likely to be achieved in nature. The large differences between Tb and Tp in some species suggest that their ancestors lived at lower latitudes and their descendents now face extreme physical challenges and have had insufficient time to evolve appropriate thermoregulatory behaviors or to make adequate physiological adaptations.