LYONS, S.K.; University of California, Santa Barbara: The effects of elevation on two aspects of local community structure of late Pleistocene mammals

Previous work examining the effect of elevation on species responses to climate change has shown that elevation has an ameliorating effect on range shifts. Because vegetation zones shift with elevation as climate changes, some mammal species will shift elevation to escape climate change. Here, I examine the relationship between elevation and community structure through time and across space. First, I examine the relationship between species range shifts and topography. Because of topography, a smaller shift in the western U.S. could allow an escape from climate change. Species whose centroid shifts occurred west of 100°W had smaller shifts than those whose centroid shifts were east of 100°W. Second, I examine the relationship between elevation and body size distributions of communities across the late Pleistocene and the globe. In general, the local body size distribution of mammal communities across the last 40 kya is similar to that of modern communities. Nonetheless, the shape of the body size distribution is correlated with elevation both across space and time. Overall, communities at higher elevations are more right skewed. In modern communities, kurtosis is negatively correlated with elevation (e.g., communities were more bimodal with higher elevation), but not in late Pleistocene communities. Quantitative analyses of the late Pleistocene of the U.S. indicate that changes in community composition through time are complex. Some geographic regions contain communities that are consistent with the expectations of individualistic range shifts, while other regions contain communities that are more similar than would be expected. This study extends that complexity to include the effects of elevation as aspects of community structure are affected by elevation across both space and time.