Alien species of plants in aquatic and semiaquatic ecosystems of the Vyatka-Kama Cis-Urals

In the territory of the Vyatka-Kama Cis-Urals, 22 species of alien macrophytes are recorded. They compose 6.5% of the number of known macrophyte species known for the region. Most of them do not play an active role in formation of vegetative communities and constitute a part of aquatic communities as accompanying elements (Amaranthus retroflexus, Chenopodium glaucum, C. rubrum, Xanthium strumarium, Epilobium pseudorubescens, Juncus gerardii, Senecio vulgaris, Typha laxmannii, Mimulus guttatus, Butomus junceus, Scirpus tabernaemontani, and Zannichellia repens). They grow in secondary and open natural ecotones and do not pose a serious threat to aquatic ecosystems in the region because of their low activity in aquatic communities. Among alien species of macrophytes, invasive species are encountered. Some of them (Najas major, Vallisneria spiralis, Phragmites altissimus, Juncus tenuis, and Echinochloa crusgalli) have become a constant part of secondary biotope communities but pose a threat to indigenous macrophyte species only in specific biotopes where ecological conditions differ significantly from normal ones. Other species (Elodea canadensis, Epilobium adenocaulon, Impatiens glandulifera, Mentha longifolia, and Lemna gibba) have successfully naturalized in natural ecosystems or have been penetrating into them. The overwhelming majority of alien macrophyte species within the region are plants which do not refer to aquatic plants: hygrophytes (ten species or 45.5%) and hygromesophytes (three species or 13.6%). Only five species (22.7%) belong to hydrophytes and four species are helophytes (18.2%). Six species of alien macrophytes are characterized by transcontinental (North America) drift, 12 species (54.5%) are characterized by transzonal drift, and four species (18.2%) have been introduced from adjacent natural zones.