Lizards on ice: Comparative thermal tolerances of the world's southernmost gecko

(1) We measured thermal tolerances (critical thermal minimum, CTmin and panting threshold, Tpant) for four populations of Homonota darwinii spanning most of the latitudinal range of the species. (2) CTmin differed across populations, but not latitudinally as predicted, likely because latitude was not as good a proxy for operative temperatures (Te). (3) Some populations had subzero CTmin indicating supercooling or freeze tolerance—the first time either phenomenon has been reported for a gecko. (4) Tpant did not differ significantly among populations. (5) The thermal tolerance breadth appears to be correlated with thermal variability in the environment. (6) Annual Te data indicate gecko retreats play a crucial role in surviving extreme surface temperatures (<0 or >50 °C).

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