Assessment of the potential of introduction, establishment and further spread of invasive alien plant species of European Union concern in Lithuania.
The list of invasive alien species of European Union concern currently includes 23 plant species. The aim of this study was to assess the potential and importance of introduction pathways for invasive alien plant species in Lithuania, to estimate probability of their establishment and further spread in the country. Analysis of all available information revealed that three species (Asclepias syriaca, Heracleum sosnowskyi and Impatiens glandulifera) currently occur in Lithuania and the latter two are widespread invasive species in the country. The remaining 20 plant species have not been registered in the wild in Lithuania so far. Four of these, Gunnera tinctoria, Lysichiton americanus, Myriophyllum aquaticum and Pennisetum setaceum, are occasionally cultivated in gardens or other outdoor areas, and six species, e.g. Cabomba caroliniana, Eichhornia crassipes, Lagarosiphon major, are cultivated in aquaria or other indoor spaces. Naturalization of seven species is unlikely in the country, whereas naturalization of 13 species (Lysichiton americanus, Myriophyllum aquaticum, Pennisetum setaceum, etc.) is plausible. Five of the analysed and still not recorded species are recognized as potentially invasive in Lithuania; the invasion of five species is plausible and that of 10 species is unlikely. The most important pathway of introduction of the analysed species is ornamental gardening. Three species that have not been recorded in Lithuania, but occur in the neighbouring regions of Europe (Elodea nuttallii, Heracleum mantegazzianum, Heracleum persicum) can enter the country by natural means. Importance of permanent studies and surveys on alien plants aiming to ensure early detection and eradication of invasive species is discussed.