Examining native and exotic species diversity in European riparian forests

This study performs a meta-analysis of existing studies of European riparian forests to investigate which exotic species have successfully established in intact riparian forests and which characteristics of these forests correspond with successful establishment. We used analysis of covariance models to investigate the relationship between community species richness, percent exotic species, and several environmental variables. We found a total richness of 1380 species, of which 45 (3.3%) were exotic. Species-rich communities generally had the higher percentage of exotics, but were not significantly related to latitude or environmental variables. Exotics, in contrast, were at generally higher levels at lower latitudes and were more abundant in large river plains and communities with intermediate levels of disturbance. These results suggest that future climate change and human actions that mimic intermediate levels of disturbance may further enhance the spread of exotic species.