Invasion in a diversity hotspot: Exotic cover and native richness in the Californian serpentine flora

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Exotic species have been observed to be more prevalent in sites where the richness of native species is highest, possibly reflecting variation among sites in resources, propagule supply, heterogeneity, or disturbance. However, such a pattern leaves unclear whether natives at species-rich sites are subject to especially severe impacts from exotics as a result. We considered this question using path models in which relationships between exotic cover and native richness were evaluated in the presence of correlated environmental factors. At 109 sites on serpentine soils across California, USA, exotic cover was positively correlated with total native herbaceous richness and was negatively correlated with the richness of both serpentine-endemic and rare native herbs. However, in path models that accounted for the influences of soil chemistry, disturbance, overstory cover, and regional rainfall and elevation, we found no indication that exotic cover reduced any component of native herb richness. Rather, our results indicated similarities and differences in the conditions favoring exotic, native, endemic, and rare species. Our results suggest that, in spite of some localized impacts, exotic species are not exerting a detectable overall effect on the community richness of the unique native flora of Californian serpentine. ?? 2006 by the Ecological Society of America.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Invasion in a diversity hotspot: Exotic cover and native richness in the Californian serpentine flora
Series title Ecology
DOI 10.1890/05-0778
Volume 87
Issue 3
Year Published 2006
Language English
Publisher Wiley
Contributing office(s) National Wetlands Research Center
Description 9 p.
First page 695
Last page 703
Country United States
State California
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