Alien aquatic plant species in European countries

Hussner A (2012). Alien aquatic plant species in European countries. Weed Research52, 297306. Summary Alien aquatic plant species cause serious ecological and economic impacts to European freshwater ecosystems. This study presents a comprehensive overview of all alien aquatic plants in Europe, their places of origin and their distribution within the 46 European countries. In total, 96 aquatic species from 30 families have been reported as aliens from at least one European country. Most alien aquatic plants are native to Northern America, followed by Asia and Southern America. Elodea canadensis is the most widespread alien aquatic plant in Europe, reported from 41 European countries. Azolla filiculoides ranks second (25), followed by Vallisneria spiralis (22) and Elodea nuttallii (20). The highest number of alien aquatic plant species has been found in Italy and France (34 species), followed by Germany (27), Belgium and Hungary (both 26) and the Netherlands (24). Even though the number of alien aquatic plants seems relatively small, the European and Mediterranean Plant Protection Organization (EPPO, ) has listed 18 of these species as invasive or potentially invasive within the EPPO region. As ornamental trade has been regarded as the major pathway for the introduction of alien aquatic plants, trading bans seem to be the most effective option to reduce the risk of further unintended entry of alien aquatic plants into Europe.