Soil seed banks as predictors of invasiveness of alien plants

Identifying reliable predictors of plant species’ invasiveness, the ability of a species to become established and spread in its non-native range, represents a pressing research question in invasion ecology. Soil seed banks are a major source of propagules and genetic diversity, thus playing a key role in the recruitment and persistence of many species reproducing by seeds. Yet, only recently the characteristics of the seed bank have started to be included among potential predictors of invasiveness. To assess the role of seed bank traits in plant invasions, (1) we compared the type (transient vs. persistent) and density of the seed bank of invasive congeners and non-invasive congeners, in their non-native range, and (2) in their native range; and (3) we compared seed bank traits of invasive species in their native and non-native range. To address these questions, we used a dataset comprising 15240 records, for 2002 species, including 149 genera for which seed bank data for invasive and non-invasive congeners are available (759 species), and 196 invasive species for which seed bank data are available in their native and non-native range. The results indicate that, in their non-native range, invasive species have a higher probability to form a persistent seed bank than their non-invasive congeners, suggesting that seed bank persistence is an important determinant of plant species’ invasiveness. Moreover, invasive species were more likely to form a persistent seed bank in their non-native rather than native range, suggesting rapid adaptive changes towards more persistent seeds. The final results of models of seed bank type and density accounting for taxonomy and phylogeny will be presented, providing insights into the role of seed bank traits as determinants of invasiveness and the importance of adaptation and pre-adaptation with respect to these traits in the successful establishment of alien species in their non-native range.