The utility of body size as a functional trait to link the past and present in a diverse reptile clade

Functional traits are important for forecasting biotic response to climate change. However, the fit of traits to environment is often poorly understood across habits and habitats. We test the functional relationship of body size to climate and the role of metabolism in governing size in turtles. Complex relationships between size and environment in modern turtles suggest that temperature-dependent metabolism is not a primary functional driver of maximum size and that human impacts and other biotic interactions have disrupted modern turtle body size distributions. Using modern trait-environment relationships to estimate paleoenvironments in the fossil record can coarsely predict paleoclimate. Further inclusion of fossil data to examine functional traits may improve the ability to assess and forecast future responses.