Denslow, M.W. , Murrell, Zack E. .
Is there a general pattern of exotic species richness along elevational gradients?
Species richness generally decreases from low to high elevations. The shape of this response varies from humped to monotonic, and may reflect the length of the sampled gradient, indicating a sampling effect. Previous studies along elevational gradients have focused on total species richness, and relatively few have investigated how patterns of native and exotic species richness differ. We used floristic studies (floras) to test and compare the patterns of native and exotic plant species richness from sea level (Atlantic coast) to the summit of the Appalachian Mountains. The use of floras enabled us to investigate elevational patterns of richness over a large gradient. We modeled the effects of size of study area, year of study, and elevation on species richness using a dataset of 68 floristic studies. Native and exotic species responded similarly along the area gradient (similar slopes of the species area relationship). Both groups were positively related to year of study, though the overall strength of richness by year was weak. After accounting for area and year, native and exotic species had contrasting richness patterns along the elevational gradient. These results suggest that different processes may govern native and exotic plant richness patterns. In addition, these findings could indicate that contemporary factors are important in shaping exotic species assemblages. We compared our findings with a survey of the existing literature and found that a general pattern has not yet been established. Lastly, we propose that human influences should be considered when interpreting diversity patterns at large spatial scales for both native and exotic species.
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1 - Appalachian State University, Department of Biology, Box 32027, Boone, North Carolina, 28608, U.S.A.
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood B/Snowbird Center
Date: Monday, July 27th, 2009
Time: 1:30 PM