Thermal ecology of allopatric lizards (Sphenomorphus) in southeast Australia : II. Physiological aspects of thermoregulation

Abstract

Physiological aspects of thermoregulation are examined in each of four species which constitute the Sphenomorphus quoyi species complex (an allopatric group of lizards, with similar Voluntary temperatures, restricted to southeast Australia).The smallest species (S. kosciuskoi) has a restricted and disjunct distribution at high altitudes. The largest species (S. quoyi) is restricted to lower altitudes. The other two species (S. tympanum - warm temperate, S. tympanum-cool temperate are intermediate in size and their combined allopatric distribution extends from low to high altitudes.Percentage integument reflectance of S. kosciuskoi is slightly lower than for the values of the other species. The species with the highest percentage integument reflectance is S. quoyi.In controlled laboratory conditions, the rate of body temperature increase at 29.5 and 10.5° C is greater than the rate of body temperature decrease in all species. Rate of heating and rate of cooling is similar in all species.It is concluded that interspecific differences in these physiological aspects of thermoregulation are slight and the differential control of heat flux by physiological means cannot account for the maintenance of similar Voluntary temperatures, in these lizards, where different habitats are utilized.