Aim The percentage of alien species found in a given habitat depends on the habitat vulnerability to invasion (invasibility) and the number of species introduced (propagule pressure). However, the global pool of alien species suited to a given habitat also varies. Here, we identify donor habitats of invasive alien plant species originating from Europe, examine the match between habitats they occupy in Europe and recipient areas and test whether donor habitats of invasive plants tend to be vulnerable or resistant to invasions.Location Europe (source area), North America and the World (recipient areas).Methods Native European vascular plants invasive in North America and other parts of the World were identified for 35 European natural habitats. Percentages of species invasive outside Europe, of the total number of native species occurring in each European habitat, were used to compare these habitats as donors for invasion. Habitat preferences of European species in their recipient areas were compared with those in Europe.Results European alluvial forests, alder carrs and coastal sand-dunes harbour the highest percentages of native species that are invasive outside Europe. Outside their native range, European species tend to invade habitats that are similar to their donor habitats in Europe, but species of alluvial and coastal habitats also frequently invade other habitats. European habitats that are important donors of invasive species globally experience the highest levels of invasion by alien species from other regions; this relationship was, however, not confirmed for invasions to North America if considered separately.Main conclusions Some European habitats are more important donors of invasive plants than others. Therefore, the level of invasion of different habitats is affected also by the differences in the number of invasive species provided by various donor habitats. At a global scale, more important donor habitats are also likely to be more invaded.

The success of European plant species as aliens worldwide is thought to reflect their association with human-disturbed environments. However, an explicit test including all human-made, seminatural and natural habitat types of Europe, and their contributions as donor habitats of naturalized species to the rest of the globe, has been missing. Here we combine two databases, the European Vegetation Checklist and the Global Naturalized Alien Flora, to assess how human influence in European habitats affects the probability of naturalization of their plant species on other continents. A total of 9,875 native European vascular plant species were assigned to 39 European habitat types; of these, 2,550 species have become naturalized somewhere in the world. Species that occur in both human-made habitats and seminatural or natural habitats in Europe have the highest probability of naturalization (64.7% and 64.5% of them have naturalized). Species associated only with human-made or seminatural habitats still have a significantly higher probability of becoming naturalized (41.7% and 28.6%, respectively) than species confined to natural habitats (19.4%). Species associated with arable land and human settlements were recorded as naturalized in the largest number of regions worldwide. Our findings highlight that plant species' association with native-range habitats disturbed by human activities, combined with broad habitat range, play an important role in shaping global patterns of plant invasions.

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AimWe hypothesize that the level of plant invasion at the scale of vegetation plots is affected by the different sizes of regional species pools of alien plants adapted to particular habitats. We test these species-pool effects in the context of alien species exchange between analogous habitats on two continents.Location North and South Carolina, and the Czech Republic (both as native and invaded range). MethodsWe identified native and alien vascular plant species within 6059 vegetation plots from 27 habitats of eastern North America and Central Europe. We compared the habitats' level of invasion, expressed as the proportion of alien species in a representative sample of vegetation plots from each habitat, with the contribution of each habitat to the alien species pool, calculated as the proportion of species of this habitat that are native to one continent and donated as aliens to the other. ResultsA habitat's level of invasion on one continent increases with the proportion of alien species donated to its regional species pools by analogous habitats on the other continent, i.e. the more of its native species a habitat contributes as aliens, the more of them establish in analogous recipient habitats (direct species-pool effect). The habitat's level of invasion on the same continent also increases with the proportion of native species that those habitats themselves donate to regional species pools on the other continent, i.e. a habitat that gives many aliens also receives many aliens (reciprocal species-pool effect). Main conclusionsWe demonstrate that when a habitat on one continent donates more of its native species to the alien species pool, the analogous habitat on the recipient continent also contains a greater number of aliens. The same donor habitat is itself also the recipient of more alien species invading from the analogous habitats of other continents. KeywordsAlien species pool, exotic species, habitat level of invasion, invaded range, native range, plant invasions.