Physiology–microhabitat matching may help organisms cope with the thermal and hydric challenges under climate change: a tale of two lizards

Climate change is significantly affecting biodiversity, and organisms that depend on external temperature – such as ectotherms – are particularly vulnerable to these effects. Microhabitats provide refuge for species, thereby reducing exposure to thermal and hydric stress under climate change. Using a mechanistic modelling approach, we assessed how microhabitat variability and physiological traits influence activity behaviour, time spent in preferred temperature, shade selection, and water loss under different climate change scenarios on two green lizard species. We classified study area microhabitats using high-resolution geospatial data and applied biophysical models to simulate organismal responses under current and future climate change scenarios (+2°C and +4°C). We first calibrated microhabitat-specific microclimate models using field data and adjusting key parameters that determine surface energy balance and soil heat transfer, including surface roughness height, substrate longwave emissivity, and soil density. We then performed steady-state ectotherm models and extracted physiological responses such as foraging and basking times, times spent in preferred temperature, selected shade, and water loss under current and projected climate scenarios. Our results revealed differences between species in terms of thermoregulatory and water-loss dynamics: Timon lepidus showed higher foraging and basking activity, particularly in open rocky microhabitats. In contrast, Lacerta schreiberi relied more on shaded vegetated microhabitats and exhibited higher size-corrected evaporative water loss. Foraging activity in T. lepidus increased in low-slope areas, whereas L. schreiberi foraged more in steeper microhabitats, where both species also selected greater shade. Activity increased on south/west slopes, while shade selection was greater on north/west slopes. Activity periods may increase under warming conditions, but this may come at the cost of higher selected shade and water loss. These results go beyond recognizing the buffering role of microhabitats in climate change, by linking fine-scale thermal and hydric variation to physiological strategies of lizard species. By integrating microclimate and ectotherm models, our work illustrates how species-specific traits interact with microhabitat heterogeneity to shape differential vulnerability under warming conditions.