Does daily climate variation have an effect on species’ elevational range size?

Abstract

In their recent paper published in Science (2016, 351, 1437–1439), Chan et al. analysed 137 montane gradients, concluding that they found a novel pattern—a negative relationship between mean elevational range size of species and daily temperature variation, which was claimed as empirical evidence for a novel macrophysiological principle (Gilchrist's hypothesis). This intriguing possibility was their key conceptual contribution. Unfortunately, as we show, the empirical evidence was flawed because of errors in the analyses and substantial sampling bias in the data. First, we re-ran their analyses using their data, finding that their model should have been rejected. Second, we performed two additional re-analyses of their data, addressing biases and pseudoreplication in different ways, both times again rejecting the evidence claimed to support Gilchrist's hypothesis. These results overturn the key empirical findings of Chan et al.'s study. Therefore, the “macrophysiological principle” should be regarded as currently remaining unsupported by empirical evidence.