Differences in Thermal Preference and Tolerance among Three Phrynocephalus Lizards (Agamidae) with Different Body Sizes and Habitat Use

We acclimated adults of two viviparous (Phrynocephalus guinanensis and P. vlangalii) and one oviparous (P. versicolor) species of toad-headed lizards (Agamidae) to 28 °C, 33 °C and 38 °C to examine whether thermal preference (preferred body temperature, Tp) and thermal tolerance (critical thermal minimum, CTMin; critical thermal maximum, CTMax) were affected by acclimation temperature, and correlate with body size and habitat use. Both Tp and CTMax were highest in P. versicolor and lowest in P. vlangalii, with P. guinanensis in between. The two viviparous species did not differ in CTMin and thermal tolerance range, and they both were more resistant to low temperatures and had a wider range of thermal tolerance than the oviparous species. Both CTMin and CTMax shifted upward as acclimation temperature increased in all the three species. Tp was higher in the lizards acclimated to 33 °C than in those to 28 °C or 38 °C. The range of thermal tolerance was wider in the lizards acclimated to 28 °C than in those to 33 °C or 38 °C. The data showed that: 1) thermal preference and tolerance were affected by acclimation temperature, and differed among the three species of Phrynocephalus lizards with different body sizes and habitat uses; 2) both Tp and CTMax were higher in the species exchanging heat more rapidly with the environment, and CTMin was higher in the species using warmer habitats during the active season; and 3) thermal preference and tolerance might correlat with body size and habitat use in Phrynocephalus lizards.