Thermal tolerance and altitudinal distribution of two Sphenomorphus lizards in Taiwan

1.We compared the thermal tolerances of a high-altitude skink, Sphenomorphus taiwanensis with that of the lowland S. incognitus to test whether their thermal tolerances correspond to their altitudinal distributions.2.We measured the critical body temperatures, the CTMax and the CTMin, of the two species under three different acclimation temperature regimes (low: 10 °C for S. taiwanensis; 15 °C for S. incognitus, medium: 20 °C, and high: 30 °C). We found that: (1) the critical body temperatures of these two skinks increased with an increase in acclimation temperatures, and (2) under the same acclimation temperature regime, the critical body temperature of S. taiwanensis was lower than that of S. incognitus as expected.3.We also recorded the 6-month survival rates of S. taiwanensis under three temperature settings (10, 20, and 30 °C). The survival rate of S. taiwanensis at 30 °C dropped to 0% in 186 days accompanied with significant reduction in body weight over time. S. taiwanensis kept at 10 °C had a survival rate of 100% with no significant change in body weight. Individuals of S. taiwanensis kept at 20 °C had a survival rate of 84.6% and a significant increase in body weight.4.We concluded that the thermal tolerances of S. taiwanensis and S. incognitus corresponded to their altitudinal distributions and that environmental temperature might be a limiting factor for their current altitudinal distributions.