Research Article |
Corresponding author: Gianniantonio Domina ( gianniantonio.domina@unipa.it ) Academic editor: Gabriele Galasso
© 2021 Emilio Di Gristina, Gianniantonio Domina, Giulio Barone.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Di Gristina E, Domina G, Barone G (2021) The alien vascular flora of Stromboli and Vulcano (Aeolian Islands, Italy). Italian Botanist 12: 63-75. https://doi.org/10.3897/italianbotanist.12.74033
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The updated censuses of the alien flora of the islands of Stromboli and Vulcano, Aeolian Islands in the Central Tyrrhenian Sea, are presented here. They currently consist of 40 and 57 specific and subspecific taxa respectively. As many as 16 and 18 taxa respectively are new in comparison with the last censuses in 2016. Mesembryanthemum × vascosilvae, commonly cultivated in both islands, is reported for the first time as naturalized alien to Italy. Passiflora incarnata from Stromboli and Pelargonium graveolens from Vulcano are reported for the first time as casual aliens to Sicily. The evolution over time of these florulas, as inferred from the main floristic works published on these islands, is commented on. Biology, ecology and possible causes of settlement of these plants are discussed briefly.
New records, Mesembryanthemum × vascosilvae, Passiflora incarnata, Pelargonium graveolens, Xenophytes
The key distinguishing factor between native and alien taxa is whether their presence in a region is due directly or indirectly to human activities (
Alien species, and in particular invasive ones, are arousing particular interest in the scientific community because they are considered one of the greatest dangers to biodiversity and an effective cost to communities (
In this study we wanted to provide an updated account of the alien vascular floras found on the islands of Stromboli and Vulcano in the archipelago of the Aeolian Islands (Italy). These two islands have a clearly visible volcanic activity and attract every year a high tourist flow for their naturalistic and landscape interest.
The floras of the Aeolian islands have been systematically studied since the first half of the 19th century. Giovanni Gussone has visited all the circumsicilian archipelagos and reports in the Prodromus (
Hence the need to prepare this summary that gives a knowledge base for the administrators and managers of these areas who need the most complete and updated data to be able to make informed choices for the conscious management of greenery in the anthropized and semi-natural environments of these territories.
Stromboli is the northernmost island of the Aeolian Islands and the most distant from the mainland (55 km). It covers an area of 12.2 km², with an elevation of 926 m a.s.l. It hosts the homonymous volcano, considered one of the most active in the world. There are two main residential areas, San Vincenzo and Piscità on the north-eastern side, and the village of Ginostra on the western side. The main activities of its inhabitants, until the 70s of the 20th century, were agriculture and fishing. Currently the main source of livelihood is tourism. In 1971, before the tourist boom, there were 400 residents, today there are 639 (
Vulcano is the southernmost island of the Aeolian archipelago and the closest to the mainland (20 km). It has an area of 20.87 Km2 and reaches an altitude of 499 m a.s.l. The last eruption of Vulcano occurred in 1890. The volcano is currently considered quiescent and the activity of fumaroles is the most evident one. At present the island’s economy is based on tourism. The island of the volcano saw intense industrial activity around the port for the extraction of volcanic products, mainly sulphur and alum until the early 20th century. The central part of the island, and the flat surroundings of the port were used for agriculture. Traces of this activity remain in the central part of the island. The surroundings of the port and the Vulcanello peninsula have been affected, since the sixties of the 20th century, by intense tourist construction that has heavily modified the landscape of the island (
Despite the authors have twenty years of knowledge of the islands, the floristic investigation for this contribution was carried out with specific field surveys in various seasons since 2016. The presence and distribution of all alien plant species observed was recorded, assessing the invasive status.
Trivial plants were identified in situ; the problematic specimens were collected or photographed and then identified using the reference flora of the territory (
Alien species were mainly recorded in the altimetric range from sea level to 100 m a.s.l. on Stromboli, on Vulcano from sea level to 50 m a.s.l. around the town of the port and between 300 and 400 m a.s.l. in the centre of the island. More than 80% of the taxa surveyed are neophytes. Inhabited areas are the most prone to host alien species. This is justified by the fact that the large part of these plants was introduced voluntarily as ornamentals. In many cases these aliens have also colonized agricultural areas. In the small islands, where spaces are limited, it is easy to have mixed land uses, finding purely ornamental plants grown alongside vegetable gardens and seeing fruit trees used as ornamental plants.
Overall, 62 alien species and subspecies were found growing wild in the two islands, 40 in Stromboli and 57 in Vulcano. The list includes 6 archaeophytes introduced in Italy before the discovery of Americas, and 56 neophytes. In Stromboli there are 5 casual, 29 naturalized and 6 invasive taxa; in Vulcano 13, 39 and 5 taxa respectively (Table
Characteristics of the alien flora of Stromboli and Vulcano: life forms, chorology, introduction time, invasiveness, habitat, pathways of introduction, reproductive strategy adopted, means of Ellenberg’s indicator values.
Life form | Stromboli | Vulcano | ||
---|---|---|---|---|
no. | % | no. | % | |
T | 12 | 30.00 | 16 | 28.07 |
G | 4 | 10.00 | 5 | 8.77 |
H | 2 | 5.00 | 2 | 3.51 |
Ch | 5 | 12.50 | 6 | 10.53 |
NP | 1 | 2.50 | 3 | 5.26 |
P | 16 | 40.00 | 25 | 43.86 |
TOT | 40 | 100.00 | 57 | 100.00 |
Chorology | Stromboli | Vulcano | ||
no. | % | no. | % | |
Africa | 6 | 15.00 | 9 | 15.79 |
America | 21 | 52.50 | 24 | 42.11 |
Australia | 3 | 7.50 | 5 | 8.77 |
Asia | 2 | 5.00 | 6 | 10.53 |
Europe & Mediterranean | 1 | 2.50 | 3 | 5.26 |
Wide distribution | 4 | 10.00 | 8 | 14.04 |
Cultigen | 3 | 7.50 | 2 | 3.51 |
TOT | 40 | 100.00 | 57 | 100.00 |
Introduction time | Stromboli | Vulcano | ||
no. | % | no. | % | |
Archaeophyte | 2 | 5.00 | 5 | 8.77 |
Neophyte | 38 | 95.00 | 52 | 91.23 |
TOT | 40 | 100.00 | 57 | 100.00 |
Invasiveness | Stromboli | Vulcano | ||
no. | % | no. | % | |
Casual | 5 | 12.50 | 13 | 22.81 |
Naturalized | 29 | 72.50 | 39 | 68.42 |
Invasive | 6 | 15.00 | 5 | 8.77 |
TOT | 40 | 100.00 | 57 | 100.00 |
Habitat | Stromboli | Vulcano | ||
agricultural | 24 | 25 | ||
inhabited | 34 | 47 | ||
reforestation | 3 | 4 | ||
roads | 10 | 15 | ||
rocky outcrops | 2 | 2 | ||
beaches and inland sands | 6 | 5 | ||
Pathway of introduction | Stromboli | Vulcano | ||
unintentional | 10 | 13 | ||
agriculture | 9 | 9 | ||
forestry | 4 | 6 | ||
industry | 3 | 2 | ||
ornament | 24 | 37 | ||
Reproductive strategy | Stromboli | Vulcano | ||
seed | 36 | 51 | ||
vegetative | 15 | 19 | ||
Ellenberg’s Indicator Values Means | Stromboli | Vulcano | ||
L | 8.13 | 8.60 | ||
T | 8.65 | 8.74 | ||
K | 4.76 | 4.69 | ||
F | 3.80 | 3.68 | ||
R | 5.56 | 5.26 | ||
N | 4.56 | 4.07 | ||
S | 0.15 | 0.16 |
a Mesembryanthemum × vascosilvae naturalized in Stromboli b Passiflora incarnata on sands in Stromboli near San Vincenzo c Pelargonium graveolens and Saccharum biflorum in Vulcano along the roads d abaxial leaf surface of Lantana camara subsp. aculeata from Stromboli e Opuntia dillenii on a wall in Stromboli at Piscità f Datura wrightii grown spontaneously in a flower bed in Vulcano and treated as an ornamental.
The species that have proved to be fearsome invasive occupying large surfaces and showing the ability to modify the environment in which they are located are: Ailanthus altissima (Mill.) Swingle, Arundo donax L., Carpobrotus acinaciformis (L.) L.Bolus in Stromboli, Oxalis pes-caprae L., and Saccharum biflorum Forssk. (Fig.
The diachronic comparison of the main floristic checklists of Stromboli and Vulcano allowed us to appreciate the exponential increasing number of alien plants (Fig.
Stromboli and Vulcano, despite having similar biological, environmental and climatic conditions, so that they are classified in the same synthetic cartography subunit (
The data here presented underline the need of integrated policies for a more conscious use of the territory. This approach should promote the use of traditional agriculture, cultivation techniques and traditional cultivars of agricultural and ornamental plants rather than the embellishment of temporary vacation places with species spread throughout the globe. All this to aim at an environmental restoration, characterizing the landscape while making it pleasant and unique in the eyes of the residents and of the visitors.
We are grateful to N.M.G. Ardenghi for assistance in identifying the Iris and Vitis taxa, to G. Galasso in identifying the Lantana and Mesembryanthemum ones.
Table with the species and subspecies of alien vascular plants present in the islands of Stromboli and Vulcano
Data type: occurences and biological data
Explanation note: The following data are included: family; life form (according to