Epilobium brachycarpum: a fast-spreading neophyte in Germany.
Only a small proportion of introduced plant species become invasive and may eventually create ecological or economic problems. In many species it is still not clear which traits cause biological invasions. As a case study we focussed on the fast-spreading Epilobium brachycarpum in Central Europe to investigate the potential of this species to become a transformer or agricultural weed. We (1) documented the spread of the species in Central Europe, (2) modelled its range and (3) seed dispersal, (4) described its phytosociological alignment, (5) analysed the traits of invaded vegetation types, (6) described seed production, population densities and life cycle, (7) did competition and germination tests, and (8) drafted a risk assessment. Relevant traits and characteristics of E. brachycarpum are (i) formation of dense stands under ruderal conditions, (ii) high seed production, (iii) effective seed dispersal, (iv) high competitiveness on bare soils against other ruderal plants, and (v) ecological niche shift compared to its native range. We expect E. brachycarpum to settle in the Mediterranean, sub-Mediterranean and many parts of temperate Europe within the next decades in habitats strongly altered by human activities, especially open stands of the alliance Sisymbrion. We predict that E. brachycarpum will become a noxious weed in vineyards, and that it will also colonise vegetation of the alliances Bidention and Carici-Epilobion.