Non‐native species drive biotic homogenization, but it depends on the realm, beta diversity facet and study design: a meta‐analytic systematic review

While reducing the species richness of invaded communities is a well-known consequence of biological invasions, non-native species can also reduce variability between communities over time (i.e. beta diversity) in a process known as biotic homogenization. Although biotic homogenization due to non-native species is a common topic of theoretical reviews, we believe no global meta-analysis on the effect of non-native species on beta diversity has been carried out yet. Here, we systematically show that non-native species drive biotic homogenization, but it depends on the realm, beta diversity facet and study design. Biotic homogenization was more intense in marine and freshwater ecosystems than in terrestrial ecosystems. We also found that non-native species reduced both taxonomic and phylogenetic beta diversity, but not the functional beta diversity. Finally, we observed more intense effects using 'before versus after invasion' followed by 'uninvaded versus invaded sites' while the effect size of studies using 'communities associated with native versus non-native species' did not differ from zero. Our findings highlight that non-native species contribute to biotic homogenization as a prevalent pattern in communities worldwide, and that biodiversity conservation strategies should go beyond investigating the reduction in the number of species by also taking into account beta diversity in its multiple facets.