DENSLOW M. W. (Department of Biology, Appalachian State University, Boone, NC 28608), M. W. PALMER (Department of Botany, Oklahoma State University, Stillwater, OK 74078), AND Z. E. MURRELL (Department of Biology, Appalachian State University, Boone, NC 28608). Patterns of native and exotic vascular plant richness along an elevational gradient from sea level to the summit of the Appalachian Mou...