Notulae to the Italian alien vascular flora: 15

A floristic compilation has expanded the documented alien vascular flora of Italy with new regional and national records, confirmed previously uncertain reports, reassigned misidentified specimens and designated one widespread cactus as an invasive alien species new to Umbria. The study brings together field observations, cultivated specimens, photographs, herbarium material and previous literature rather than reporting a single controlled experiment. Most of the new records were classified as casual aliens, while a smaller number were judged naturalized or invasive. The observations span urban flowerbeds, roadsides, riverbanks, fields, cemeteries, coastal rocks, former olive-growing terraces and other sites across Italy.

Three maples provided the first alien records for Trentino-Alto Adige. Acer buergerianum Miq. subsp. buergerianum was documented in Lavis at the local railway station, where a few young plants, each below 50 centimetres high, grew in an urban flowerbed at an elevation of 212 metres. Acer palmatum Thunb. was found near Tenna, where an individual grew on the bank of the Vignola creek at 480 metres. Acer tataricum L. subsp. ginnala was recorded along the Vena creek near Levico Terme, with several individuals at 436 metres. These observations were dated between 2021 and 2022 and were identified as casual alien taxa new to the regional flora.

Other first regional records came from ornamental escapes in southern and northern Italy. Aesculus hippocastanum was found at Mastrocianni near Vico del Gargano in Puglia, and Aloë perfoliata was observed in flowering condition in arid coastal garrigue near Torre Sibiliana in Petrosino, Sicily. Calocedrus decurrens was recorded in a shaded, ivy-covered corner of the San Cataldo cemetery in Modena. The single tree, estimated to be three to five years old and 23 centimetres tall, stood about 40 metres from four mature ornamental trees. A young Cedrus atlantica was found on dry-stone walls near Pornassio in Liguria, where other plants about 30–40 centimetres high grew near Forte Centrale, with adult cultivated trees in the surrounding area identified as their source.

Catalpa bignonioides was added to the alien flora of Tuscany after young and fruiting individuals were found beside a channelized river near an industrial area in Siena. Its identification was distinguished from Catalpa ovata through leaf morphology: C. ovata has a trilobate leaf blade, whereas C. bignonioides has an entire blade. The authors also separated C. bignonioides from C. speciosa by seed-body dimensions and shape, reporting 4.5–5.5 by 30–42 millimetres for C. bignonioides, with sides drawn out to an acute apex, compared with 5.5–7.5 by 26–31 millimetres and an obtuse apex for C. speciosa. Elsewhere, Jasminum nudiflorum was recorded in soil pockets on rock in the historic centre of Vico del Gargano.

Several new records involved plants growing in heavily disturbed ground. Bidens sulphurea was found in flower beside a road in Potenza, Basilicata. Oenothera speciosa covered about 30 square metres of untended ground with synanthropic vegetation in the Chieti Scalo district of Abruzzo. Physalis philadelphica was represented by one specimen beside a road near a gypsum quarry at Scafa, also in Abruzzo. Petunia axillaris, described in the study as an annual herb native to temperate southern America and characterized by a white hypocraterimorph corolla, was found growing in pavement interstices in Palermo, where mature individuals were present. Perilla frutescens was added to the Campanian alien flora from a roadside plant in Naples.

Alien grasses supplied further regional records. Digitaria violascens was found in several individuals beside a road between Falcinello and Ponzano Superiore in Liguria. Ehrharta erecta was documented on beaches at Santo Stefano al Mare and Arma di Taggia, both in the province of Imperia. Eragrostis mexicana subsp. virescens was recorded beside a road in Viggiano, Basilicata, after collection and identification by F. Santi and confirmation by E. Banfi. Gazania linearis was added to the Campanian flora from a beach south of Torre dei Caprioli. The record dates to 1994, and specimens previously cited from Cilento as Gazania rigens were reassigned to G. linearis using the published identification key of Laguna Lumbreraras and Ferrer Gallego.

The compilation also documented plants judged to be naturalized outside cultivation. Impatiens parviflora was recorded along the Tronto River in the Gran Sasso and Monti della Laga National Park in Marche, where it occurred sporadically in a riparian megaforb community at 660 metres. Solanum nitidibaccatum was found in numerous individuals across three contiguous fields in Acquanegra Cremonese, Lombardy, growing among maize stubble. Ruellia simplex was recorded along Corso Tukory in Palermo and in pots and flowerbeds near a cultivated specimen in the Palermo Botanical Garden. Saxifraga stolonifera colonized a few square metres of uncultivated terracing and dry-stone walls beside a road at Mergozzo in Piedmont.

Taxonomic review of preserved material led to two notable exclusions from regional lists. Records of Datura innoxia in Piedmont were reassigned to Datura wrightii. This included specimens from Alba and Baldissero d’Alba cited in earlier work, material from Pocapaglia, an 1879 specimen collected in Bra, and a specimen from Viverone. A 2002 report from Mondonio in the municipality of Castelnuovo Don Bosco could not be verified because no linked specimens were available, its then-recorded ephemeral population was no longer confirmed, and the available photograph appeared to show D. wrightii. D. innoxia was therefore excluded from the alien flora of Piedmont. In a separate record, D. wrightii was added to the flora of Valle d’Aosta from ruderal ground west of a former railway station in Chambave.

Sardinia provided another correction. A review of the available literature concluded that all naturalized bamboo populations previously attributed to Bambusa vulgaris should instead be assigned to Phyllostachys aurea. The variegated form Bambusa vulgaris ‘Vittata’ continues to be cultivated ornamentally in some gardens, but the literature review did not support its attribution to the naturalized Sardinian populations. The revision therefore excluded B. vulgaris from the alien flora of Sardinia while recognizing P. aurea as the species represented by those previously reported populations. The record was based on reassessment of published evidence rather than a new population survey.

The most extensive new record involved the cactus Opuntia stricta, which was classified as an invasive alien species new to the flora of Umbria. It was recorded at Le Pisciarelle in Terni and at additional localities in the province of Terni, including Casteldilago in Arrone and two sites in Fornole and Sambucetole in Amelia. The plants occupied terraces of former olive groves, clearings with holm oak and Aleppo pine, natural cliffs and artificial escarpments. At a locality upstream of Fornole, about 31 hectares were covered. The authors also stated that O. stricta may have hybridized with Opuntia humifusa at Le Pisciarelle because the two occurred in the same habitat. On an inaccessible rocky slope below Casteldilago, O. microdasys was recorded as a naturalized alien new to Umbria, while O. monacantha was confirmed as a casual alien and was found among numerous individuals of O. humifusa.

One first record for Italy was made by Paspalum denticulatum in Milan, where it was found naturalized in urban turf around a monument in Largo Cairoli and beside a tree-lined road on Via Monte Cimone. The species is native to central and southern America and belongs to a group of four taxa sometimes treated as synonyms, including the better-known Paspalum lividum. Even when the two species are kept separate, the Italian specimens were considered to fit P. denticulatum more closely on morphological grounds, particularly because their leaf blades reached a width of up to 9 millimetres. The article’s broader contribution lies in combining new field observations with specimen-based revisions and literature checks, providing a more precise regional baseline while distinguishing isolated alien plants, naturalized populations and the much more extensive occurrence of O. stricta.

Subject of Research: New records, taxonomic reassessments and distribution updates for alien vascular plants in Italy

Article Title: Notulae to the Italian alien vascular flora: 15

Article References: Galasso, G., Domina, G., Argenti, C., Bajona, E., Banfi, E., Barberis, D., Barone, G., Bartolucci, F., Biscotti, N., Bonali, F., Bonifazio, C., Bonsanto, D., Buldrini, F., Cannucci, S., Cozzolino, A., De Natale, A., Del Guacchio, E., Di Gristina, E., Fiaschi, T., … Lastrucci, L. (2023). Notulae to the Italian alien vascular flora: 15. Italian Botanist, 15, 77-89. https://doi.org/10.3897/italianbotanist.15.105794

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.15.105794

Keywords: Italian flora, alien plants, invasive species, botanical records, Opuntia stricta, Opuntia microdasys, Paspalum denticulatum, herbarium taxonomy, ornamental escapes, Umbria, Notulae, Italian