Clues on the warming vulnerability of a water frog Telmatobius rubigo (Anura: Telmatobiidae) from the arid Central Andes of Argentina

Warming climate is one of the main threats affecting the fitness and survival of amphibians, the most threatened vertebrate class. Proxies such as the critical thermal maximum (CTmax) and the thermal safety margin, which can change during the ontogeny, have been developed to know the vulnerability to warming. Telmatobius rubigo is a fully aquatic frog of high-altitude lotic freshwater ecosystems and is an endemic species from the Central Andean Puna ecoregion of north-western Argentina. The species lives and reproduces in shallow permanent streams, which could represent a challenge in a warming climate because the water's high heat capacity and thermal diffusivity allow an amphibian to exchange heat with its environment rapidly. Here, we study thermal biology traits—field-body temperature, operative range of environmental temperatures and upper thermal limits—of T. rubigo during the warmer months of the year to estimate the species’ tolerance to a warming climate. Telmatobius rubigo has field-body temperatures positively related to water temperatures. A positive association between the daily means of air and water temperatures was observed for the warmer months in the microhabitat occupied by T. rubigo. A similar association was observed for daily maximum air and water temperatures in warmer months. Despite the wide variability of air temperatures in the highlands where T. rubigo lives, the species' refuges have a narrow water temperature range during the day. An intraspecific variation in upper thermal limits—CTmax and thermal safety margin—due to ontogenetic stages was observed, with tadpoles more tolerant to heating than adults. This study presents the most comprehensive data on the thermal biology of one species of the Telmatobiidae family providing suggestions to guide further studies on high-altitude aquatic amphibians. Keywords: amphibian, climate crisis, high-altitude stream, thermal biology, CTmax