Skinks not (yet) on the brink : thermal performance of tropical lizards across multiple spatial scales

Abstract

Consequences of climate change in ectotherms, such as extinctions and range shifts, vary in magnitude according to thermal physiology and local environments. Generally, greater thermal heterogeneity in space and time is believed to confer better resilience to these impacts. However, the relationship between environmental variability and physiology can vary depending on the scope of a given spatial scale. Accordingly, the central objective in this thesis is to test this hypothesis in Scincidae lizards at two habitat scales. I employed sprint speed to model thermal performance curves, quantifying thermal physiology for comparisons across habitats. I then estimated their current thermal suitability as potential activity time and applied warming scenarios to determine if the lizards from less thermally heterogeneous habitats might be more vulnerable to climate change. I found support for the hypothesis in the second, broader scaled study presented in this thesis, where I projected forest skinks to be vulnerable to climate change while the ecotone skinks would benefit. In the first study, I found that thermal environments were similar across habitats, concordant with my results showing equal thermal tolerance breadths. However, comparing thermal performance, I also found evidence that the forest skink species is more likely to eventually be at risk relative to the stream species. Therefore, based on these studies alone, thermal heterogeneity could be associated with greater resilience to climate change at the larger spatial scale, yet not necessarily at the smaller scale. Although I did not detect a straightforward and ubiquitous pattern, I applied a fundamental niche approach to climate change impact predictions which focuses on the direct relationship between thermal physiology and the local environment. With this method, I further demonstrated the complexity of the relationship between thermal environments and associated warming implications in ectotherms.