PARENT SESSION
Poster Session # 16: Invasive Species.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Predicting plant invasion in North American ecoregions: A macroecological approach.
Stark, Scott1, Bunker, Daniel1, Carson, Walter1, 1 University of Pittsburgh, Pittsburgh, PA
ABSTRACT- Over three thousand exotic (i.e., non-native) plants currently dwell in the United States and Canada. Biological invasion (i.e., the influx of successful exotics) is implicated in the decline and extinction of native organisms. Ecologists have correlated species' traits with invasion success and ecosystem properties with invasibility. For instance, the diversity-invasibility hypothesis predicts that diverse native ecosystems should resist invasion and thus exotic richness should decline with increasing native richness. However, recent macroecological work has shown that these comparisons can be confounded if the effects of area are not considered. Here we compare species-area curves between exotic and native plants across the major ecological units (e.g., boreal forest, grassland) of the United States and Canada. If the slope of species-area curves differ between native and exotic species, then processes structuring these communities are likely to differ. The dependence of species richness on area (i.e., slope of the species-area curve) differs between ecoregions but is strikingly similar for exotic and native species within individual ecoregions. This suggests that exotic fraction (exotic richness / native richness: a common metric of invasion) is an area-independent metric that may be employed in site comparisons within certain ecosystems. However, some ecosystems may not follow this generalization (e.g., grasslands). After controlling for area dependence we tested the diversity-invasibility hypothesis at large scales. Within U.S. states and Canadian provinces, area-corrected native and exotic richness have a strong positive correlation (r2=0.42). In agreement with the findings of other recent studies, the diversity invasibility hypothesis is not supported at large scales.
Key words: biogeography, invasibility, invasions, diversity