Assessing climate change vulnerability in a broadly ranging lizard: eco-physiological and thermal niche approaches

One of the principal causes of biodiversity loss and the sixth mass extinction is global climate change. Lizards, from tropical lowlands to cold high-mountain sites, are vulnerable to extinction due to their temperature dependence and the increasing environmental temperature. We modelled the projected local extirpation risk of the Mesquite lizard Sceloporus grammicus Wiegmann, 1828, the most widespread lizard species in Mexico. We integrated operative and microclimatic temperatures, eco-physiological traits (locomotor performance, and voluntary thermal range), distribution records and climate projections up to 2050 and 2070 under two climate change scenarios (Representative Concentration Pathways: RCP 4.5 and 8.5). Our eco-physiological model predicted a high risk of the projected local extirpation and thermally suitable area loss in both RCP scenarios and for both projections. We found a probability of projected local extirpation risk ranging from 25.1% to 39.4% and a probability of thermally suitable area loss ranging from 31% to 61% between the RCP 4.5 scenario in 2050 and RCP 8.5 scenario in 2070. Among the 90 terrestrial Protected Areas (PAs) evaluated, S. grammicus has historical occurrence in only 29 PAs for the current scenario (thermally suitable area of 51 250 km²) and only 23 PAs under RCP 8.5 for 2070 (29 505 km²) representing a reduction in thermally suitable area of more than 40% with only 23 historical occurrences within the Mexican PAs. Our results align with prior studies on this species and Sceloporus, showing that S. grammicus, despite a broad latitudinal and altitudinal distribution, is highly susceptible to the negative impacts of climate change. Mechanistic models are a powerful tool for evaluating reptile vulnerability, emphasizing physiological data as key to improving climate-response projections. These findings are directly applicable to conservation proposals.