Thermal ecology of two sympatric saxicolous lizards of the genus Phymaturus from the Payunia region (Argentina)

• Preferred temperatures of Phymaturus roigorum and Phymaturus payuniae are around 34–35 °C.
• P. payuniae reach higher field body temperatures than P. roigorum.
• The accuracy and effectiveness of thermoregulation are better in P. payuniae than in P. roigorum.
• P. payuniae avoids occupying sites where dark basalts are predominant.

We evaluated the thermal biology of two sympatric saxicolous species of the genus Phymaturus, endemic from the Argentine Payunia region. Taking into account that the distributional range of Phymaturus roigorum (the largest species) is greater than the range of P. payuniae, we evaluated the habitat (type of rocks) used by these species. We recorded body temperature and operative temperatures in different habitats, and we determined the preferred body temperature in the laboratory. We compared the thermal quality of habitats occupied and not occupied by Phymaturus payuniae, and the accuracy and effectiveness of thermoregulation between species.P. roigorum was found on many different kinds of rocks, but P. payuniae was found mainly on two types or rocks and not found on dark basalts. No differences were found in habitat thermal quality or in preferred temperatures when comparing among populations or between species. Although both species are thermoregulators, P. payuniae demonstrated better accuracy and effectiveness. This is the first study to assess thermal biology in coexisting species of the genus Phymaturus and provides the first data on effectiveness of thermoregulation for the genus. The results obtained have importance from a conservation perspective, since both endemic species are vulnerable and no data on habitat or thermal requirements were available up till now.