Global warming is seriously threatening amphibians. One of the main causes is the direct effect of the increase in average and extreme temperatures, in addition to the indirect consequences that entail the destruction and fragmentation of their terrestrial and aquatic habitats. On the other hand, we have very little information of the traits associated with thermal physiology, especially in tropical species that constitute more than 85% of amphibian species. A thorough knowledge of the features associated with tolerance and thermal sensitivity, that define the fundamental thermal niche of these species, and the description of the climatic features both micro and macroclimatic of their habitats, are essential to predict the responses of amphibians to address climate change consequences on amphibian communities.
We have analysed the interspecific variation in thermal tolerance limits (CTmax, CTmin and thermal breath) and thermal performance curves (optimum temperature (Top), thermal breadth (B80)) of an amphibian community along an altitudinal gradient in Ecuador. This allowed us to estimate the vulnerability to suffer acute and chronic thermal stress based on the temperatures measured at the micro (dataloggers) and macroenvironmental level (WorldClim) in different species of tadpoles (75) and adults of the genus Pristimantis (20), collected from lowlands either from the Pacific coast and the Amazon basin to the Andean highlands (5m – 4200 m).
We found a decrease in the thermal limits along the altitudinal gradient, being greater the decline in cold tolerance values. This asymmetric reduction of the thermal limits determined that high elevation species have greater thermal ranges. In addition, we found that species of open or deforested biomes, which are exposed to a higher level of climate variability, have greater thermal tolerance ranges. We also tested the hypothesis of climate variability in altitude, which predicts that increased thermal tolerance range in ectotherms correlates with a wider distribution on altitude. Finally, our results suggest that lowland species are more vulnerable to heat stress which could determine in the worse cases an increased risk of extinction due to global warming.