Inter-population thermal ecology and assessment of climate change vulnerability in the endemic mexican mountain cloud forest stream frog Ptychohyla leonhardschultzei (Anura: Hylidae) using a correlative and mechanistic approach

Amphibians are highly susceptible to abrupt environmental changes. The objectives of this study were to describe the inter-population thermal ecology and to assess the vulnerability of the stream frog Ptychohyla leonhardschultzei an endemic species of high-altitude cloud forests with a limited and fragmented distribution to climate change, using a correlative and mechanistic approach To assess the vulnerability of P. leonhardschultzei , we compared the climatic suitability under current conditions across the species’ known distribution with two contrasting future scenarios (SSP245 and SSP585), using a correlative modelling approach. The results for the worst-case scenario from this model were validated using Sinervo´s mechanistic restriction-hours model, which involved the study of the interpopulational thermal ecology of three populations. Our results indicated significant differences in the habitat conditions among the study sites and in the thermal physiology of the populations. For the species, the most frequent environment temperature remained within the selected temperature range (Tset: 18.5 – 21.6 ° C) and the thermal tolerance range (RTT: 8.94±1.99 -28.78±1.59 ° C). The optimal locomotor performance (Topt) was 25°C, and the broad thermal performance breadth (B80) ranged from 10°C to 25°C. We observed abrupt declines in mean climatic suitability, which fell to ≤ 58.17% across its entire distribution under all scenarios evaluated by the correlative model. Differences between scenarios (SSP245 and SSP585) ranged from 5.42 to 18.95%, with a mean of only 3.10 hours of activity (Ha) for the worst scenario. Our findings suggest that P. leonhardschultzei may face a high risk of extinction by the year 2100 under the worst scenario, SSP585.