Biological invasions of alien aquatic plants are a major threat to conservation of freshwater habi­tats, as well as a socio-economic problem. Introduced primarily by human activities, these alien plants compete with native species, reduce local biodiversity and alter structure and function of the aquatic ecosystems. This review examines the most relevant scientific literature on the major invasive alien aquatic plants (IAAPs) found in Europe (Alternanthera philoxeroides, Azolla filiculoides, Cabomba caroliniana, Egeria densa, Elodea canadensis, E. nuttallii, Gymnocoronis spilanthoides, Hydrilla verticillata, Hydrocotyle ranunculoides, Lagarosiphon major, Lemna minuta, Ludwigia grandiflora, L. hexapetala, L. peploides subsp. montevidensis, Myriophyllum aquaticum, M. heterophyllum, Pistia stratiotes, Pontederia crassipes, Salvinia molesta), with a special focus on impacts exerted by these species on invaded freshwater ecosystems. It includes both qualitative and quantitative analyses and evaluates the temporal trends of the scientific contributions considering the impact and management of these species in Europe and worldwide. Despite a recent increase in contributions on these IAAPs, the knowledge on their impacts in Europe remains mainly concentrated on a few species and rather fragmented and deficient on others. In fact, evident inequalities emerge among these IAAPs in both the number of dedicated contributions and in the treatment of each species, as some of them are currently excluded from the list of IAS of Union Concern. Moreover, the European level research on these IAAPs turned out to be scarcely influenced by the “listing” effect (i.e. inclusion of IAAPs in the Union list), showing little or no increase in the number of studies on impact or management. The studies found on impacts document that the selected IAAPs largely exert environmental impacts on invaded ecosystems by altering both the abiotic (water chemical and physical factors) and biotic (plant and animal communities) components. The impact mechanisms of these species vary (chemical, physical, structural, competitive, toxicity) and were classified according to the EICAT (Environmental Impact Classification for Alien Taxa) protocol. Overall, the review reveals significant gaps in knowledge about the environmental impacts of most of these IAAPs in Europe, despite some being included in the list of IAS of Union concern. To address these gaps and protect European freshwater ecosystems from biological invasions, more field studies supported by laboratory investigations are needed, followed by effective management interventions. In addition, it is considered necessary that impactful alien species with a wide distribution in Europe, but which are currently excluded from the EU list, be included as soon as possible. This would allow for coordinated management practices at the European level, which are essential for their containment.

A comprehensive floristic study on the vascular flora of the 11 Italian volcanic lake calderas is presented. Despite encompassing one of the Mediterranean’s major freshwater systems, floristic research in these areas has proved fragmented and often outdated. By integrating literature data with original data from new floristic surveys, a total of 1182 spontaneous plant taxa were recorded, including 152 alien plants. Six taxa represent regional novelties and 102 are new for the study area, while 48 taxa reported before 1950 were not confirmed locally. From a conservation perspective, 27 taxa of national interest were reported, including two species classified as Critically Endangered (Isoëtes sabatina, Vicia incisa) and four Endangered (Carex vulpina, Baldellia ranunculoides, Hippuris vulgaris, Hydrocotyle vulgaris) according to IUCN criteria, along with 50 taxa listed on regional red lists. Floristic richness varies notably, from 124 taxa in the caldera of Lake Giulianello to 756 in Lake Bracciano, reflecting differences in caldera size, degree of anthropogenic impact and availability of previous botanical data. These results significantly enrich the floristic knowledge of the calderas of Italian volcanic lakes and may represent a solid reference for future naturalistic research in these areas.

Freshwater lakes are fundamental ecosystems that provide essential ecosystem services for humans and support high plant diversity, often including specialized and rare species. Nevertheless, in Italy, botanical knowledge of lake ecosystems remains fragmented, and floristic data are scattered across heterogeneous sources. DataLake is a dataset designed to integrate and standardize existing floristic knowledge on aquatic and riparian vascular plants occurring in 30 natural freshwater lakes of central-southern Italy. Records included in DataLake derive from both literature sources and original field surveys conducted by the authors. Overall, DataLake comprises 5140 georeferenced floristic records referring to 213 taxa, 97 genera and 43 families. The dataset highlights a markedly uneven distribution of taxa and records among lakes, with large tectonic and volcanic basins accounting for the highest floristic richness and number of records. The taxonomic composition is dominated by Cyperaceae, Potamogetonaceae and Juncaceae, while at the species level Myriophyllum spicatum L., Ceratophyllum demersum L., Phragmites australis (Cav.) Trin. ex Steud., Potamogeton perfoliatus L. and Stuckenia pectinata (L.) Börner are the most frequently recorded taxa. A substantial proportion of taxa is included in regional (39% of the dataset) and national (10.8%) conservation risk categories, underlining the role of lacustrine ecosystems as important reservoirs for plant species of conservation concern. Alien species were recorded in 14 lakes, and among these, 12 taxa are classified as invasive, including Paspalum distichum L., Elodea canadensis Michx. and Bidens frondosa L.. Biological and chorological spectra reflect the strong ecological dependence of lacustrine plant species on hydrological conditions, with dominance of hydrophytes and helophytes and multizonal taxa. By integrating heterogeneous floristic data into a single, coherent and openly accessible resource, DataLake provides a solid reference base for future floristic research, as well as for supporting long-term monitoring activities and actions aimed at conserving natural Mediterranean freshwater lake ecosystems.

A multitemporal floristic study was conducted on the aquatic and riparian plant communities of the lower stretch of the Tiber River (central Italy) to identify any floristic changes in response to possible environmental pressures that have occurred locally over time. This investigation was carried out by comparing α- and temporal β-diversity, as well as biological, chorological, and ecological traits of plant assemblages present in permanent plots (n = 24) and sampled at two different time points (2005, 2025). Although both aquatic and riparian plant communities showed an increase in α-diversity over time (+94.1% and +56.5%, respectively), they generally exhibited different temporal patterns. The aquatic community showed a more stable floristic structure compared to the riparian one, with a persistent dominance of eutrophic and pollution-tolerant species, although local disappearance/rarefaction of some species was recorded. On the contrary, the riparian community showed greater species turnover, mainly due to an increase in generalist, ruderal and alien species, which over time have partially replaced those typically associated with riparian habitats. Ecological trait-based analyses indicated an increase over time in the percentage of thermophilous, heliophilous and nitrophilous species in both plant communities; the riparian community also showed an increase in xerophilous ones. Overall, the results indicate that aquatic and riparian communities exhibit distinct temporal dynamics within the same river system and highlight how long-term, permanent plot-based floristic monitoring is a useful tool in environmental studies.