The tradition of floristic studies in Italy has made it possible to obtain a good knowledge of plant diversity both on a national and regional scale. However, the lack of knowledge for some areas, advances in plant systematics and human activities related to globalization, highlight the need for further studies aimed at improving floristic knowledge. In this paper, based on fieldwork and herbaria and literature surveys, we update the knowledge on the Italian vascular flora and analyze the floristic similarities between the administrative regions. Four taxa, all exotic, were recorded for the first time in Italy and Europe. In detail, Elaeodendron croceum, Kalanchoë blossfeldiana, and Sedum spathulifolium var. spathulifolium were found as casual aliens, while Oxalis brasiliensis was reported as historical record based on some herbarium specimens. Furthermore, Kalanchoë laxiflora was confirmed as a casual alien species for Italy and Europe. Status changes for some taxa were proposed at both national and regional levels, as well as many taxa were reported as new or confirmed at the regional level. Currently the Italian vascular flora comprises 9150 taxa of which 7547 are native (of which 1598 are Italian endemics) and 1603 are exotic at the national level. The multivariate analysis of updated floristic data on a regional scale showed a clear distribution along the latitudinal gradient, in accordance with the natural geographical location of the regions in Italy. This pattern of plants distribution was not affected by the introduction of alien species. Despite some taxonomic and methodological issues which are still open, the data obtained confirm the important role of floristic investigations in the field and in herbaria, as well as the collaborative approach among botanists, in order to improve the knowledge of the Italian and European vascular flora.

Knowledge on alien species is needed nowadays to protect natural habitats and prevent ecological damage. The presence of new alien plant species in Italy is increasing every day. Calabria, its southernmost region, is not yet well known with regard to this aspect. Thanks to fieldwork, sampling, and observing many exotic plants in Calabria, here, we report new data on 34 alien taxa. In particular, we found three new taxa for Europe (Cascabela thevetia, Ipomoea setosa subsp. pavonii, and Tecoma stans), three new for Italy (Brugmansia aurea, Narcissus ‘Cotinga’, and Narcissus ‘Erlicheer’), one new one for the Italian Peninsula (Luffa aegyptiaca), and 21 new taxa for Calabria (Allium cepa, Asparagus setaceus, Bassia scoparia, Beta vulgaris subsp. vulgaris, Bidens formosa, Casuarina equisetifolia, Cedrus atlantica, Chlorophytum comosum, Cucurbita maxima subsp. maxima, Dolichandra unguis-cati, Fagopyrum esculentum, Freesia alba, Juglans regia, Kalanchoë delagoënsis, Passiflora caerulea, Portulaca grandiflora, Prunus armeniaca, Prunus dulcis, Solanum tuberosum, Tradescantia sillamontana, and Washingtonia filifera). Furthermore, we provide the first geolocalized record of Araujia sericifera, the confirmation of Oxalis stricta, and propose a change of status for four taxa (Cenchrus setaceus, Salpichroa origanifolia, Sesbania punicea, and Nothoscordum gracile) for Calabria. The updated knowledge on the presence of new alien species in Calabria, in Italy and in Europe could allow for the prevention of other new entries and to eliminate this potential ecological threat to natural habitats.

Despite the importance for scientific and conservation purposes, the knowledge of the Italian territory is far from exhaustive. New chorological data for 87 vascular taxa regarding the central-southern part of Italy and its two main islands (Sicilia and Sardegna) are presented. Among these taxa, Epilobium nummularifolium, Metrosideros excelsa, and Salvinia minima are recorded as casual aliens for the first time in Europe (excluding Azores and Madeira for M. excelsa), while Cyclamen balearicum and Polygala rupestris are reported for the first time and confirmed for Italian native flora, respectively. Furthermore, several taxa are new or confirmed at regional level. Finally, Lathyrus cirrhosus, Urginea fugax, and Linum tenuifolium are excluded from Italy, continental and peninsular Italy, and Sardegna, respectively.

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, exclusions, and status changes for Italy or for Italian administrative regions of taxa in the genera Bunias, Calocedrus, Calycanthus, Celosia, Clerodendrum, Convolvulus, Crassula, Cyclamen, Datura, Dicliptera, Eragrostis, Erigeron, Gamochaeta, Gazania, Impatiens, Kolkwitzia, Leucaena, Ludwigia, Medicago, Muscari, Nigella, Oenothera, Opuntia, Paulownia, Petroselinum, Phyllostachys, Physalis, Pseudosasa, Quercus, Reynoutria, Roldana, Saccharum, Sedum, Semiarundinaria, Senecio, Sisyrinchium, Solanum, Sporobolus, Tulipa, Vachellia, Verbena, and Youngia. Nomenclatural and distribution updates published elsewhere are provided as Suppl. material 1.

Despite the wide amount of scientific contributions published on alien plant species, their diffusion dynamics, and their interactions with native taxa, it is increasingly difficult to slow down their spreading and their negative impact on habitats. Last recent years, in fact, a sharp rise in the number of new alien plant taxa introduced in Italy and Europe has been recorded. The aim of this work is to investigate most of the Italian territory in order to verify whether this alarming trend is still underway. Specimen collections and/or observations of alien plants have been performed in as many as 12 Italian regions. All the collected specimens are stored in public or private herbaria. Taxa have been identified according to the literature from the countries of origin of the investigated taxa, while the nomenclature followed the current international references. Updates on 106 taxa are reported. In particular, among 117 new records, 89 are first records, 27 are changes to status and there is 1 extinction. Seven new taxa for Italian alien flora are reported, two of which are new to Europe. The administrative regions with the highest number of records are Calabria (48), Sardegna (17) and Sicilia (15). Five of the surveyed taxa, for the first time, have been considered invasive aliens to Italian territory. The unfrequent amount of original results provided by this work, over the simple importance of data itself, proves how floristic investigation, still today, represents one of the most effective tools in broadening the current knowledge about alien taxa and their dynamics.

In this contribution, new data concerning the distribution of vascular flora alien to Italy are presented. It includes new records, confirmations, and status changes for Italy or for Italian administrative regions of taxa in the genera Abies, Actinidia, Aloe, Amaryllis, Anredera, Arctotheca, Bidens, Cardiospermum, Celosia, Commelina, Cotoneaster, Cyclamen, Eclipta, Euphorbia, Grevillea, Hedera, Hibiscus, Impatiens, Juglans, Kalanchoe, Koelreuteria, Lindernia, Melinis, Myriophyllum, Nandina, Nicotiana, Oenothera, Oxalis, Parthenocissus, Phoenix, Phyllanthus, Physalis, Plumbago, Pteris, Quercus, Setaria, Symphytum, Tagetes, and Washingtonia. Nomenclatural and distribution updates, published elsewhere are provided as Suppl. material 1.