Thermal ecology in island populations of the Aegean wall lizard (Podarcis erhardii)

Background/Question/Methods

Global climate change has been impacting natural ecosystems globally, and is expected to lead to numerous species extinctions. The effects are predicted to be particularly severe for populations that have been reduced and isolated through anthropogenic habitat fragmentation. Despite the worldwide occurrence of both phenomena, we have only a poor understanding of how habitat fragmentation (and the associated loss in genetic diversity) renders species susceptible to climate change. In this study, we investigate how habitat fragmentation and the concomitant loss in genetic diversity affect the thermal preferences of different populations of a model ectothermic organism. We take advantage of a well-characterized, natural fragmentation process, during which land-bridge islands were formed by rising sea levels in the Aegean Sea (Greece). These islands harbor relict populations of Aegean Wall lizards (Podarcis erhardii, Lacertidae) which are very poor over-water dispersers and which have lost different amounts of their original genetic diversity through drift.

Results/Conclusions

We quantified aspects of thermal and physiological ecology in populations from one large, genetically diverse baseline island, as well as two offshore islets. This allowed us to determine whether environmental differences (on the large island) or genetic impoverishment (on the small islets) affect the thermal and physiological ecology of the species. Although populations across the three islands did not differ in mean or variance of field body temperatures, thermal tolerances, or in selected (“preferred”) temperatures, we did find significant differences in water loss rates corresponding to dryness of the habitat. Our results suggest that loss of genetic diversity does not appear to affect thermal ecology, while locally prevailing conditions do.