Data and Code for "Naturalized tree species in the Anthropocene: Climate surpasses geography in shaping beta diversity"

Aim: Assessing to what degree the spread of naturalized alien tree species has changed their taxonomic and phylogenetic beta diversities globally, and whether the factors driving those diversity patterns have shifted.

Location: Globe.

Time period: From the 15th century to the present time.

Major taxa studied: Tree.

Methods: For 1,844 naturalized tree species, we compiled data on their native and naturalized ranges and assessed the magnitude of changes in taxonomic and phylogenetic beta diversity resulting from the global spread of these alien species. Additionally, we examined the relative contributions of climatic factors, geographic distance, and trade to their beta diversity before and after human-mediated spread.

Results: The spread of naturalized tree species has reduced their beta diversity of the 50 subcontinental TDWG-2 regions globally, i.e., causing substantial biotic homogenization in naturalized tree floras. Notably, we found that distant regions have become more similar in species composition than regions that are adjacent to or share a boundary with each other. Although a positive relationship between taxonomic and phylogenetic similarities was observed, taxonomic similarity showed a tendency for stronger changes. Geographic distance was the most influential factor in shaping both taxonomic similarity before naturalization, while temperature became dominant after naturalization. Contrary to expectations, trade intensity had only a marginal effect on both taxonomic and phylogenetic similarity after naturalization.

Main conclusions: Our study highlights the widespread expansion of naturalized tree species and their contribution to global biotic homogenization in naturalized tree floras. The results emphasize the diminished role of geographic distance and the growing influence of temperature in shaping species similarities after naturalization. Projections of intensifying human activities and ongoing climate change suggest that the composition of naturalized tree species is likely to undergo further reshuffling in the future, potentially reshaping the fundamental spatial structure of the biosphere.