The impact of insularity on the thermoregulation of a Mediterranean lizard

• We assessed the impact of insularity on lizard thermoregulation.
• Insular habitats were of higher thermal quality than the mainland ones.
• Mainland lizards showed high Tpref but both populations achieved similar field Tb.
• Island lizards thermoregulated less effectively.
• Predation may be a potential factor that prevent mainland lizards from achieving field Tb within its Tset.

The overall biology of ectotherms is strongly affected by the thermal quality of the environment. The particular conditions prevailing on islands have a strong effect on numerous features of animal life. In this study we compared mainland and island populations of the lizard Lacerta trilineata and hypothesized that insularity would affect the thermoregulatory strategy. Continental habitats were of lower thermal quality, experiencing more intense fluctuations and had higher values of operative temperatures. Nevertheless mainland lizards selected for higher body temperatures in the lab and showed more effective thermoregulation during summer than their island peers. Lizards achieved similar body temperatures in the field in both types of habitat, underlining the importance of predation as a potential factor to mainland lizards that failed to reach their higher thermal preferences. Both island and mainland populations of L. trilineata have been adapted to their thermal environment, supporting the labile view on the evolution of thermal physiology for this species.