Elevational and microclimatic drivers of thermal tolerance in Andean Pristimantis frogs

Aim: We analysed elevational and microclimatic drivers of thermal tolerance diversity in a tropical mountain frog clade to test three macrophysiological predictions: less spatial variation in upper than lower thermal limits (Bretts’ heat invariant hypothesis); narrower thermal tolerance ranges in habitats with less variation in temperature (Janzen´s climatic variability hypothesis); and higher level of heat impacts at lower altitudes.
Location: Forest and open habitats through a 4230 m elevational gradient across the tropical Andes of Ecuador.
Method: We examined variability in critical thermal limits (CTmax, and CTmin), and thermal breadth (CTmax-CTmin) in 21 species of Pristimantis frogs. Additionally, we monitored maximum and minimum temperatures at the local-scale (tmax, tmin), and estimated vulnerability to acute thermal stress from heat (CTmax-tmax) and cold (tmin – CTmin), by partitioning thermal diversity into elevational and microclimatic variation.
Results: Our results were...