Impacts of Solidago gigantea on other species at home and away

Much attention has been paid to the ecological impacts of invasive plants in their non-native ranges, but few studies have compared these impacts to those in the native ranges of invaders. This is important because biogeographical differences in species interactions suggest that evolutionary history might affect community assembly and thus contribute to our understanding of invasion. We correlated stem densities of Solidago gigantea, native to North America but highly invasive in Europe, with associated plant species richness in plots measured over large areas of the northwestern USA and Hungary. We also compared the effects of Solidago root extracts on the growth of plant species native to Europe and North America and that were common in our field sampling in each region. Increasing stem density of Solidago correlated with significant decreases in total species diversity and native species diversity in Europe, but not in North America. Extracts made from Solidago roots suppressed the root and shoot growth of a suite of species native to Europe and co-occurring with Solidago, more than co-occurring North American species as a group. Our results are consistent with a growing body of literature demonstrating a strong biogeographic context to exotic plant invasions. This body of work indicates that the biogeographic origin of species can affect community organization and that communities with a common evolutionary history might function differently than those that do not share such a history.