Patterns of distribution of anurans in high Andean tropical elevations: Insights from integrating biogeography and evolutionary physiology

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Abstract
Among ectothermic tetrapods, amphibians are by far the most diverse group at high elevations in the tropical Andes. This article asks whether this pattern reflects intrinsic aspects of amphibian natural history. An interdisciplinary analysis suggests that amphibians have a long evolutionary history at moderate Andean elevations and that adaptation for activity at low temperature occurred frequently and independently in different taxa. One conclusion is that temperature is unlikely to be the only or the main factor constraining some unrepresented anuran taxa that do not reach high elevations. Other physical variables (e.g. the effects of ultraviolet radiation on egg development) could better explain anuran diversity along tropical altitudinal gradients. In contrast, heliothermic taxa, such as lizards, might indeed be constrained by the low and variable temperatures that characterize high tropical elevations. Ecological gradients, therefore, might not affect ectothermic tetrapods in a similar manner, and differential susceptibility to biotic and abiotic factors that change with elevation might help to explain current patterns of distribution and diversity.