CONICET | Buscador de Institutos y Recursos Humanos

Temperature is one of the major factors affecting lizard?s physiology, hence the availability of thermally suitable microhabitats for thermoregulation behaviours becomes fundamental to achieve and maintain body temperatures within a favourable range for vital activities such as reproduction, feeding and escaping from predators. There is a degree of different interactions with the thermal environment which result in different thermal niches among species and populations. Here we compared the thermal biology in three species belonging to the family Liolaemidae, Phymaturus williamsi, P. aguanegra and Liolaemus parvus, the latter in syntopy with each of the other two species of Phymaturus in the highlands of the Andes in San Juan province, Argentina. We determined field body temperatures (Tb), preferred body temperatures in laboratory (Tpref), operative temperatures (Te) and thermoregulatory efficiency (E) using the methodology proposed by Hertz et al. (1993). Phymaturus species exhibited conservatism in Tb independently of the differences in habitat and climatic factors, while L. parvus populations showed a wide intraspecific variation in Tb suggesting higher thermal flexibility than P. williamsi and P. aguanegra. However, the Phymaturus species behaving as moderate thermoregulators (E P. aguanegra: 0.5 and E P. williamsi: 0.56) showing an index of effective thermoregulation higher than Liolaemus parvus (E L. parvus- Agua Negra: 0.48 and E L. parvus Q. Vallecito: 0.33) populations. We concluded that the species studied here occupy similar altitudinal ranges along the Andes highlands and therefore the lizards experience comparable environmental conditions and microhabitats during their activity at different time scales. Nevertheless, microhabitat preferences among species may play a role in thermoregulation. Thus, the fluctuations during day and night and seasonality in environmental temperatures in harsh habitats seem to be the most important source of variation of body temperatures in high altitude Liolaemid lizards rather than other intrinsic factors such as sex, body size or behaviour.