Chasing the Patagonian sun: comparative thermal biology of Liolaemus lizards

Abstract

The importance of the thermal environment for ectotherms and its relationship with thermal physiology and ecology is widely recognized. Several models have been proposed to explain the evolution of the thermal biology of ectotherms, but experimental studies have provided mixed support. Lizards from the Liolaemus goetschi group can be found along a wide latitudinal range across Argentina. The group is monophyletic and widely distributed, and therefore provides excellent opportunities to study the evolution of thermal biology. We studied thermal variables of 13 species of the L. goetschi group, in order to answer three questions. First, are aspects of the thermal biology of the L. goetschi group modelled by the environment or are they evolutionarily conservative? Second, have thermal characteristics of these animals co-evolved? And third, how do the patterns of co-evolution observed within the L. goetschi group compare to those in a taxonomically wider selection of species of Liolaemus? We collected data on 13 focal species and used species information of Liolaemus lizards available in the literature and additional data obtained by the authors. We tackled these questions using both conventional and phylogenetically based analyses. Our results show that lizards from the L. goetschi group and the genus Liolaemus in general vary in critical thermal minimum in relation to mean air temperature, and particularly the L. goetschi group shows that air temperature is associated with critical thermal range, as well as with body temperature. Although the effect of phylogeny cannot be ignored, our results indicate that these thermal biology aspects are modelled by cold environments of Patagonia, while other aspects (preferred body temperature and critical thermal maximum) are more conservative. We found evidence of co-evolutionary patterns between critical thermal minimum and preferred body temperature at both phylogenetic scales (the L. goetschi group and the extended sample of 68 Liolaemus species).