Ecological constraints on the evolutionary association between field and preferred temperatures in Tropidurinae lizards

Ectothermic body temperatures affect organismal performances and presumably fitness, and are strongly influenced by the thermal environment. Therefore, the processes of colonization of novel thermal habitats by lizards might involve changes in thermal preferences, performance curves (reaction norms) and field activity temperatures. According to theory based on optimality analysis, diverse aspects of the thermal biology of vertebrate ectotherms should co-evolve as to maximize performance at the temperature range more often experienced by animals in the field. One corollary of this premise is that derived lizard clades that experienced a significant shift in thermal ecology, in comparison with the ancestral condition, should prefer and select temperatures in a thermal gradient similar to those experienced in nature. Here we report an analysis of the premise stated before. Specifically, we verify whether or not Tropidurinae species from three major Brazilian habitats (the Rainforests, the semi-arid Caatingas and the Cerrados, a Savannah-like biome) differ in thermal ecology and thermoregulatory behavior. The Caatinga is believed to be the ancestral habitat of this sub-family, and differences are expected because species from semi-arid habitats usually exhibit high body temperatures for lizards, whereas forest specialists might be thermoconformers and active at low temperatures. We also compared selected temperatures in the laboratory by species from the two open habitats (Caatingas and Cerrados). Data were analyzed using both conventional and phylogenetic analysis tools. Although species from Caatingas exhibited higher activity temperatures in nature than those from Cerrados, mean selected temperatures were similar between ecological groups. Phylogenetic analyses confirmed these findings and evidenced large evolutionary divergence in field activity temperatures between sister species from different open habitats without coupled divergence in selected temperatures. Therefore, thermoregulatory behavior and ecological parameters did not evolve similarly during the colonization of contrasting open habitats by Tropidurinae.