Native and alien nymphaeids in a Mediterranean island: distribution and status in Sardinia (Italy)

After a long-term monitoring campaign spanning 1999-2025, the populations of Nymphaeids growing in Sardinia were comprehensively investigated. Within the family Nymphaeaceae, Nuphar lutea and Nymphaea alba are native species on the island, while two other taxa are alien: Nymphaea mexicana and N. × marliacea, both currently naturalized in Sardinia. Two additional taxa, one native (Nymphoides peltata) and one alien (Nelumbo nucifera) remain unconfirmed: the former was reported only once in 1827, and the latter was recorded as naturalized twenty years ago, but with no precise location or subsequent observations. Overall, we recorded the occurrence of N. alba at 166 sites (eight of which are now locally extinct) and N. lutea at 38 sites (two of which are now locally extinct). Regarding N. alba, its populations in northern Sardinia have all been described in detail, with numerous metapopulations documented, particularly within the hydrographic basins of the Coghinas, Temo, and Posada rivers, as well as in other smaller basins. Moreover, some stations in South Sardinia have been confirmed after more than a century. In addition, N. candida is definitively excluded from Sardinian flora. As for Nuphar lutea, its localities have been further refined, all concentrated in the Coghinas River basin, whereas the only known sites in the South have now disappeared. Moreover, an updated and verified distribution of exotic waterlily populations in Sardinia is provided. Furthermore, the ecological requirements, the main threats and conservation issues affecting native taxa on the island are identified.

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