Cold tolerance and altitudinal distribution of Takydromus lizards in Taiwan

We investigated whether cold tolerance was an important limiting factor in the current altitudinal distributions of two Takydromus lizards, T. formosanus (< 1500 m in altitude) and the lowland-dwelling T. stejnegeri (< 1000 m in altitude) in Taiwan. We measured their critical thermal minimum (CTMin) and 3 mo survival rates in 4 cold treatments, and compared these with a high-mountainous species, T. hsuehshanensis (> 1800 m in altitude). The results indicated that (1) both the CTMin and prolonged cold tolerance were correlated to their upper limit of altitudinal distributions as predicted and (2) T. formosanus and T. stejnegeri had reasonable survival rates at temperatures that were lower than the underground temperature of high altitudinal areas. We concluded that although cold tolerance was correlated with altitudinal distribution, it is not a crucial factor limiting T. formosanus and T. stejnegeri at higher altitudes.