Among the most striking algal findings is the confirmation of Acetabularia caliculus for Italy, discovered in August 2023 at Porto Pozzo in northern Sardinia. The species, a member of the green algae family Polyphysaceae, was found growing densely on a shoal of no more than thirty square meters near the entrance of a small gulf and lagoon, on very fine sediments at a depth of about three meters. Acetabularia caliculus is distinguished from its better-known relative A. acetabulum by a generally longer axis, a darker green terminal disc with significantly fewer rays — between 22 and 35 compared with 55 to 90 — and an upper crown formed by segments that are not fused together. Although first described from Western Australia, in the Mediterranean it had previously been recorded only from the Balearic Islands and the north-western coast of Spain, making the Sardinian population a remarkable biogeographic extension.

The charophyte green algae, close relatives of the ancestors of land plants, feature prominently in the new survey. Fieldwork in the mountain lakes of Abruzzo revealed three species of Nitella and the monotypic genus Nitellopsis new to the region. Nitella opaca, previously known in Italy from Trentino-Alto Adige, Lombardia, Veneto, Lazio and Sardegna, was found to dominate the submerged vegetation of the Montagna Spaccata reservoir and to cover large areas in the Campotosto reservoir, while remaining less abundant in the natural lake of Scanno. The species is dioecious, distinguishing it from the similar N. flexilis, and typically colonizes high-conductivity, calcium-rich waters at varying depths, requiring relatively cold water with an optimal temperature range of 12 to 15 degrees Celsius.

Nitella gracilis, another addition to the Abruzzese flora, presents a more troubling conservation picture. The species was detected only in small quantities within mats of dominant characeans in three reservoir lakes. It is a rare and endangered species across Europe: extinct in Denmark and endangered in the Balkans, Sweden and Switzerland. Its ecological optimum points to low-calcium waters, which makes its discovery in association with the calciphilous N. opaca an ecological puzzle that the authors say requires further investigation. Meanwhile, Nitellopsis obtusa — the only extant member of its genus — was found to dominate the deepest vegetation belt of Lake Campotosto, between nine and fourteen meters depth. The species is of conservation concern in much of its native European range, yet it is classified as invasive in North America, illustrating how the conservation status of a single organism can diverge sharply between continents.

A particularly satisfying note concerns the rediscovery of Nitellopsis obtusa in Basilicata. The only previous record for the region dated back more than a century, to 1908 in the Monticchio lakes, and recent work had concluded that the species was extinct there. The new find at Lago Pantano, where characeans are very rare and occur interspersed within vegetation dominated by Ceratophyllum demersum, demonstrates how long-absent species can persist undetected in overlooked water bodies. Such rediscoveries underscore the value of sustained floristic monitoring: a species absent from records for over a hundred years may simply have escaped the attention of surveyors rather than vanished from the landscape.

Among the bryophytes, several notable records emerged from the mountains of Trentino-Alto Adige. Drepanocladus turgescens, a moss with a mainly subarctic-alpine distribution in Europe and rare in the Mediterranean, was confirmed for the region after more than a century — the previous signal dated to 1904 for Passo di Resia, where it had not been reconfirmed. New collections from the Sella Group at 2,812 meters, the Brenta Group and the Pale di San Martino plateau, all on wet dolomite, establish that the species persists in the high Dolomites. Hookeria lucens, a moss of shaded and humid sites, was recorded as new to Trentino-Alto Adige from a limited settlement of a few square decimeters along the Chiese stream in a scarcely accessible and partially explored area, highlighting how much remains to be discovered even in well-studied alpine territories.

The aquatic moss Fissidens fontanus was documented as new to Trentino-Alto Adige from the Sarca river between Torbole and Arco, growing on stones at depths of 10 to 30 centimeters. The species is identified by the absence of a central strand in the stem and sheathing laminae that reach only a quarter to a third of the total leaf length. In Italy it is known from scattered records, with older data from northern regions and more recent findings in Friuli-Venezia Giulia, Toscana, Sardegna and Sicilia. Equally significant is the report of Weissia angustifolia as new to Italy, found on sunny flowerbeds in Piombino and in Mediterranean garrigue at Talamone in Toscana. The species was only recently recognized at species level, having previously been treated as a variety of W. longifolia; it differs from other European members of the genus by tightly involute margins along the distal half of the perichaetial leaves, a short seta, and an abscission zone at the junction of the operculum and urn — a combination unique among European species of the subgenus Astomum.

The fungal records concentrate on the Botanical Garden of the University of Calabria, which proved an unexpectedly rich site for rare agarics. Alnicola macrospora, Cortinarius vernus, Inocybe assimilata, Inocybe bresadolae, Leucoagaricus purpureolilacinus and Neohygrocybe ovina were all documented as new to Calabria, most of them previously known only from northern and central Italian regions. Cortinarius vernus, a spring species of the subgenus Telamonia, was identified by its strongly verrucose but broadly ellipsoid spores, longer than those of the closely related C. erythrinus. Leucoagaricus purpureolilacinus, a slender and fragile lepiotaceous fungus, has been reported in only a few Italian regions so far. The lichenicolous fungus Arthonia epiphyscia was recorded as new to Trentino-Alto Adige from Monte Castellazzo in the Dolomites at about 2,100 meters — the first collection of the species in Italy above the treeline — while the related A. phaeophysciae, a parasite on Phaeophyscia lichens that bleaches infected areas of the host thallus, was documented from Val Venosta. The rust fungus Puccinia phragmitis was also added to the Calabrian flora from its bright red stage on leaves of Rumex crispus.

Lichenology contributed some of the most ecologically revealing records. Bacidina adastra, described only in 2003 from the Netherlands and previously reported in Italy just twice from Emilia-Romagna, was found at two Lombard localities: a broadleaved woodland that has developed over the last 25 years on a former industrial site near the center of Milan, and the outskirts of an agricultural village. Both settings confirm the species’ affinity for anthropized habitats under eutrophicated conditions — a striking example of biodiversity adapting to post-industrial landscapes. Chaenotheca gracilenta, a pinhead lichen so rare in Italy that it is listed as “vulnerable” in the national Red List of epiphytic lichens, was discovered on juniper bark and roots at the entrances of prehistoric caves in Umbria, a habitat typical of the niches protected from rain that the species favors. Heterodermia speciosa, listed as “near-threatened,” was confirmed for Lazio from a moist montane beech stand on Monte Terminillo, coherent with its optimum in humid woodlands.

Finally, the survey documents taxonomic progress as well as new geography. The lichen Squamarina subcetrarioides, long treated as a variety of S. gypsacea, was shown in a 2023 molecular study to differ from the typical Mediterranean variety not only in morphology and altitudinal distribution but also genetically, and is now treated as a distinct species of the alpine and Carpathian belts. Records from Friuli-Venezia Giulia, Veneto, Trentino-Alto Adige, Piemonte, Marche and Abruzzo — some drawn from herbarium material collected decades ago — establish its presence across the Italian Alps and Apennines. Together with the rediscovery of century-old charophytes and the colonization of industrial ruins by rare lichens, the sixteenth Notulae installment demonstrates that Italy’s flora of algae, bryophytes, fungi and lichens remains far from fully mapped, and that careful fieldwork, even in familiar landscapes, continues to yield discoveries of both scientific and conservation significance.

Subject of Research: New floristic records of algae, bryophytes, fungi and lichens in Italy

Article Title: Notulae to the Italian flora of algae, bryophtes, fungi and lichens: 16

Article References: Ravera, S., Vizzini, A., Totti, C., Puglisi, M., Azzella, M. M., Battaglini, A., Bernardo, L., Bonini, I., Calvia, G., Cancellieri, L., Cantonati, M., De Giuseppe, A. B., Fačkovcová, Z., Filibeck, G., Galasso, G., Galli, R., Gheza, G., Guttová, A., Hafellner, J., … Trainito, E. (2023). Notulae to the Italian flora of algae, bryophtes, fungi and lichens: 16. Italian Botanist, 16, 105-120. https://doi.org/10.3897/italianbotanist.16.114044

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.16.114044

Keywords: Italian flora, algae, bryophytes, fungi, lichens, charophytes, biodiversity, conservation, floristic records, Acetabularia, Nitella, Squamarina