First record of Vallisneria australis in France
In 2022, almost simultaneous observations were made of the same undetermined species of submerged plant with long, ribbon-like leaves in two artificial water bodies located far apart in France, Lake Salagou (Hérault) and Lake Vaivre, near Vesoul (Haute-Saône). Both populations consist of dense populations extending over several thousand square metres. Visual examination of the plants made it possible to determine that they were both from the genus Vallisneria but the leaf morphology was different to that of the native species Vallisneria spiralis. When comparing these specimens with Vallisneria australis, it was confirmed that they were the same species and molecular analysis conducted by the Dutch Plant Protection Service also suggests that the species is very probably V. australis. The ‘very probable’ identification highlights the fact that within Europe, V. australis shows genetic variation. V. australis has been observed in Hungary, Germany, Belgium and Italy. It has been known from Hungary since the end of the 19th Century with the first observations in the thermal springs of Budapest in 1891. However, it is quite capable of establishing itself in unheated natural environments as was subsequently seen in other sites in Europe. As for the two cases in France, it has been observed that the plant occupies human modified water bodies by developing monospecific stands capable of eliminating other submerged plants. Further research is needed to confirm the identity of certain populations in France and to assess its behaviour and impacts.
Sources
Dutartre A (2022) Vallisneria australis, une nouvelle espèce aquatique exotique en France. http://especes-exotiques-envahissantes.fr/vallisneria-australis-une-nouvelle-espece-aquatique-exotique-en-france/
Mesterházy A, Somogyi G, Efremov A, Verloove V (2021) Assessing the genuine identity of alien Vallisneria (Hydrocharitaceae) species in Europe. Aquatic Botany 174, 103431, 6 pp.