Invasion history of Elodea canadensis and E. nuttallii in Italy
Elodea canadensis (Hydrocharitaceae) and E. nuttallii (EPPO List of Invasive Alien Plants) are both native to North America and are invasive alien plants within the EPPO region. The invasion history of both species was analysed in Italy, by reviewing all available herbarium, field records and literature, dating between 1850 and 2019. E. canadensis arrived in Italy before 1866 and had two invasion phases, between the 1890s and 1920s and between the 1990s and 2000s. E. nuttallii, probably arrived in the 1970s and started invading in 2000 and the invasion is still ongoing. The current invasion range of both species is centred in Northern Italy, with scattered occurrences of E. canadensis in central and southern regions. The study detects differences in the niches of the two species during the introduction and naturalisation phase and that a habitat switch occurred after 1980 in E. canadensis and after 2000 in E. nuttallii, during their expansion phases. Until 1980, canals were the most frequent habitat for E. canadensis recorded in the herbarium dataset. However, from 1990 onwards the number of E. canadensis occurrence records from rivers and lakes increased considerably, with river records exceeding canal records in 2000–2010. E. nuttallii occurred almost exclusively in lakes until 2000, but in the subsequent decade it was most frequently recorded in canals and rivers. In the last 10 years, E. canadensis was mostly found in canals, whereas E. nuttalli was mostly found in rivers, however differences in the number of occurrences between canals, rivers and lakes became less evident in both species.
Sources
Buldrini F, Pezzi G, Barbero M, Alessandrini, Amadei L, Andreatta S, Ardenghi NMG, Armiraglio S, Bagella S, Bolpagni R, Bonini I, Bouvet D, Brancaleoni L, Brundu G, Buccheri M, Buffa G, Ceschin S, Chiarucci A, Cogoni A, Domina G, Forte L, Guarino R, Gubellini L, Guglielmone L, Hofmann N, Iberite M, Lastrucci L, Lucchese F, Marcucci R, Mei G, Mossetti U, Nascimbene J, Passalacqua NG, Peccenini S, Prosser F, Repetto G, Rinaldi G, Romani E, Rosati L, Santangelo A, Scoppola A, Spampinato G, Stinca A, Tavano M, Caruso FT, Vangelisti F, Venanzoni F, Vidali M, Wilhalm T, Zonca F, Lambertini C (2023) The invasion history of Elodea canadensis and E. nuttallii (Hydrocharitaceae) in Italy from herbarium accessions, field records and historical literature. Biological Invasions 25, 827–846.