Thermal ecology of allopatric lizards (Sphenomorphus) in Southeast Australia

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Abstract
Behavioural aspects of thermoregulation are examined in each of the four species which constitute the Sphenomorphus quoyi species complex (an allopatric group of lizards, with similar Voluntary temperatures, restricted to southeast Australia). Shade air temperatures during emergence of S. quoyi and S. tympanum (warm temperate) in the field are 15.5°C and 17.5°C respectively when fifty percent of the population have emerged. Those for S. tympanum (cool temperate) and S. kosciuskoi are 10.0°C and 10.5° C respectively. Laboratory studies on emergence rendered similar temperatures to those found in the field. It appears that both ambient temperatures and commencement of the light phase may alter onset of emergence and submergence behaviour. Shuttling behaviour (movement between sunlit and shaded surfaces) is considered to be an important aspect of behavioural thermoregulation in these species. Following a consideration of the vegetation form and density associated with each species it is suggested that shuttling behaviour patterns are functional adaptations. This thermoregulatory behaviour could explain the absence of widespread sympatric populations within this species complex.