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Empirical invasion ecology is laden with high context dependency. If general mechanisms underlying invasion success exist, they should be detectable in species that share biological and ecological characteristics. We carried out a growth experiment with Agropyron cristatum, Bromus inermis and Poa pratensis (subsp. angustifolia), to better understand the mechanisms underlying the invasion success of cool‐season grasses in northern prairie grasslands of North America. By using a home–away approach, we tested whether 1) non‐native plants have a higher performance than native plants, and whether invasiveness is 2) mediated by interactions with soils, such as a release from pathogens or enhanced mutualism, or 3) an adaptation to local soils. We compared seed size and weight of populations in Canada (non‐native range) and Eurasia (native range) and carried out an experiment, in which seeds from the non‐native and native ranges were planted into sterilized soil (control) and soil from a population in Canada or Eurasia, or local soils, respectively. We found inconsistent effects across species and response variables. Seed size and weight were not significantly different between native and non‐native populations. The experiment showed a seed origin effect in A. cristatum (root and total biomass) and B. inermis (root biomass), with non‐native populations outperforming native ones. Soil‐mediated effects were supported in A. cristatum (root biomass) and local adaptation in B. inermis (root and total biomass). Germination across all species and biomass in P. pratensis did not respond to treatments. Despite the high similarity of our study group, our results indicate that invasiveness might be driven by idiosyncratic causes at the species level. Mechanisms not considered in our study, such as high propagule pressure and preadaptation could also potentially explain the invasion success across species. [ABSTRACT FROM AUTHOR]

Aim: Plant species continue to be moved outside of their native range by human activities. Here, we aim to determine whether, once introduced, plants assimilate into native communities or whether they aggregate, thus forming mosaics of native‐ and alien‐rich communities. Alien species might aggregate in their non‐native range owing to shared habitat preferences, such as their tendency to establish in high‐biomass, species‐poor areas. Location: Twenty‐two herbaceous grasslands in 14 countries, mainly in the temperate zone. Time period: 2012–2016. Major taxa studied: Plants. Methods: We used a globally coordinated survey. Within this survey, we found 46 plant species, predominantly from Eurasia, for which we had co‐occurrence data in their native and non‐native ranges. We tested for differences in co‐occurrence patterns of 46 species between their native (home) and non‐native (away) range. We also tested whether species had similar habitat preferences, by testing for differences in total biomass and species richness of the patches that species occupy in their native and non‐native ranges. Results: We found the same species to show different patterns of association depending on whether they were in their native or non‐native range. Alien species were negatively associated with native species; instead, they aggregated with other alien species in species‐poor, high‐biomass communities in their non‐native range compared with their native range. Main conclusions: The strong differences between the native (home) and non‐native (away) range in species co‐occurrence patterns are evidence that the way in which species associate with resident communities in their non‐native range is not species dependent, but is instead a property of being away from their native range. These results thus highlight that species might undergo important ecological changes when introduced away from their native range. Overall, we show origin‐dependent associations that result in novel communities, in which alien‐rich patches exist within a mosaic of native‐dominated communities. [ABSTRACT FROM AUTHOR]