Ecophysiology of a small ectotherm tracks environmental variation along an elevational cline

Aim Physiological responses to climate can be used to quantify the environmental limits that a species can tolerate and are, therefore, key to biogeographical studies. Several ecophysiological responses to climatic factors may shape the distribution of species, but our knowledge is mostly centred in thermal ecophysiology. We applied an integrative approach to investigate how ecophysiological responses of a small ectotherm are modulated by climatic variation across an elevational gradient. Location Victoria, Australia. Taxon Lampropholis guichenoti (Scincidae, Squamata). Methods We examined metabolic rate, evaporative water loss, thermal physiology and locomotor performance, of four populations of the skink Lampropholis guichenoti across an elevational gradient in Australia (17-1546 m). We applied biophysical modelling to test how behaviour impacts the survival and activity of these skinks. Results Populations from the lowlands had lower metabolic rates and evaporative water loss, lower thermal preferences, higher optimal temperatures and increased locomotor performance compared populations from high elevations. Biophysical models revealed that behaviour allows skinks from high elevation to maintain their body temperatures above freezing and is key to determining activity patterns. Main conclusions Our holistic study shows that a combination of physiological and behavioural responses allows ectotherms to survive in different climatic environments. The interplay between physiology and behaviour can help to explain how climate sets limits for the geographical range of ectotherms.