The body temperature of active amphibians along a tropical elevation gradient: patterns of mean and variance and inference from environmental data

Abstract

Summary1. Tropical montane amphibians have been the focus of recent and crucial conservation efforts. These initiatives require understanding on how elevation influences amphibian body temperature beyond the simplistic assumption of a monotonical decrease with elevation. This study addresses patterns and potential for inference in this context. 2. As elevation increases, mean body temperature (BT) of tropical montane amphibians decreases linearly, but intrapopulation variation (VAR) in BT increases exponentially. These relationships are influenced by biome structure, but display both local nuances and speciesspecific remarks. 3. Substrate temperature (ST) and BT hold a close relationship across elevation. The noise around this relationship is lowest in mid-elevation cloud forests and maximum in the paramo, a biome above the tree line. 4. The relationships between BT and ST, and between elevation and either BT or VAR, are valuable to infer general patterns of thermal ecology for amphibians and to highlight speciesspecific exceptional cases. 5. The BT of montane tropical amphibians can be estimated from temperature data collected at a scale compatible with the size and microhabitat of individual frogs. Estimates from elevation are valid as general trends that can be enhanced if natural history is taken into account. Worldclim data allow for rough inference only and have limited predictive power. 6. A framework is proposed to study how the BT and VAR of amphibians change with elevation. This framework encompasses information on biome structure and natural history.

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