Variation in thermal biology of three closely related lizard species across an elevation gradient

The critical thermal limits of organisms and the thermal sensitivity of their performance tends to vary predictably across latitudinal gradients. There has been comparatively less investigation into variation in thermal limits biology with altitude, despite similar gradients in environmental temperatures with elevation. To redress this, we examined species critical thermal limits (CTmin and CTmax); thermal sensitivity of locomotor performance, and shelter site attributes, in three lizard species that replace one another along a contiguous elevation gradient in south eastern Australia. The species examined consisted of a highland specialist, Liopholis guthega, mid elevation species L. montana, and lowland L. whitii. We found similar habitat attributes between the species, but L. guthega predominantly occurred in open habitat which may reflect a strategy for maximising exposure to insolation. We found intraspecific variation in lizard thermal traits, most notably in cold tolerance of L. guthega and in both heat and cold tolerance of L. whitii, suggesting population specific variables acting on thermal physiology rather than a species distribution maintained by distinct thermal tolerances. This study represents one of the few examinations of thermal trait variability within and between species with elevation in a temperate system, and provides evidence for thermal physiology driven by localised adaptation and/or physiological plasticity to local conditions.