25.4 Friday, Jan. 4 Global patterns of thermal tolerance and range limits predict climate change responses in ectotherms SUNDAY, JM*; BATES, AE; DULVY, NK; Department of Biological Sciences, Simon Fraser University; Institute for Marine and Antarctic Studies, University of Tasmania,; Department of Biological Sciences, Simon Fraser University email@example.com
How species ranges are shaped by environmental gradients is a central goal of ecology and has come under renewed relevance given the new challenges posed by global climate change. Here we present a comparative analysis of thermal tolerance limits in ecototherms on land in the ocean, and test the hypothesis that species occupy latitudes that correspond to their thermal tolerance windows. We find that marine and terrestrial ectotherms differ in the degree to which they fill their potential thermal ranges. Terrestrial ectotherms are excluded from the warmest regions of their latitudinal range, while marine species more fully occupy the extent of latitudes tolerable within their thermal niche. These findings suggest that terrestrial species may be less sensitive to climate warming at their warm range boundaries. We test this hypothesis by collecting global observations of climate-induced range shifts at poleward and equatorward range boundaries in systematic assemblage surveys. We find that in the ocean, shifts at both range boundaries have been equally responsive, while on land, equatorward range boundaries have lagged in their responses to climate warming, matching predictions. These results indicate that marine species’ ranges conform more closely to their limits of thermal tolerance, while terrestrial species' ranges do not. Understanding the relative contribution of other factors in controlling warm range boundaries on land is necessary for predicting the rate of local extinction at trailing range boundaries.