126 ACTA BOT. CROAT. 77 (2), 2018 Acta Bot. Croat. 77 (2), 126–134, 2018 CODEN: ABCRA 25 DOI: 10.2478/botcro-2018-0007 ISSN 0365-0588 eISSN 1847-8476 The flora and vegetation of the NE Mediterranean islet with centuries-long human influences Nenad Jasprica1, Katija Dolina1*, Milenko Milović2 1 Institute for Marine and Coastal Research, University of Dubrovnik, P.O. Box 83, HR-20000 Dubrovnik, Croatia 2 "Antun Vrančić" Grammar School, Put Gimnazije 64, HR-22000 Šibenik, Croatia Abstract – This paper is based on the main results of an analysis of spontaneous flora and vegetation on the small islet of Vrnik (0.281 km2), on which there are some abandoned limestone quarries, on the eastern Adriatic coast. The investigations were carried out from 2014 to 2016. Altogether, 251 vascular plant taxa (species and infraspecific units) were recorded on the islet. A total of 11 plant associations, one subassocation and two stands within 10 vegetation classes were identified. Due to high anthropogenic influences during the last centuries, quarrying in particular, the islet investigated showed a relatively low variety of vascular plant taxa. In addition, clear signs of fragmentation of the forest vegetation were observed. Keywords: Croatia, eastern Adriatic, phytosociology, syntaxonomy, vascular plant diversity * Corresponding author, e-mail: katija.dolina@unidu.hr Introduction The karstic islet of Vrnik on the eastern Adriatic coast (WGS84: 42°56′9″N 17°10′9″E; or according to Croatian Terrestrial Reference System 1996 (HTRS96): X=554623, Y=4755335) is part of the Korčula Archipelago situated in the channel between the Pelješac peninsula and the island of Korčula in southern Croatia (Fig. 1). The islet is the second largest in the whole Archipelago which comprises 19 islets and five rocks. Exploitation of mineral resources (architectural building stone) has a long tradition in the Archipelago, including the islet of Vrnik in particular, dating back to the Roman Em- pire (Krklec et al. 2011). The Senonian limestone was used Fig. 1. Geographical position of the islet of Vrnik in south Croatia, eastern Adriatic (Abbreviations: SLO: Slovenia; HR: Croatia; BIH: Bos- nia and Herzegovina; MNE: Montenegro; I: Italy). FLORA AND VEGETATION OF THE MEDITERRANEAN ISLET ACTA BOT. CROAT. 77 (2), 2018 127 for the construction and decoration of villas and residences in the region of Dalmatia, the city of Dubrovnik in particu- lar, but it was also exported to the Orient (e.g., Constantino- ple) and Italy (Gjivoje 1969, Krklec et al. 2011). The finding of the Lumbarda Psephisma, the most important monument written in Greek in Croatia, carved into a stone pillar which was found near to the village of Lumbarda on the island of Korčula, suggests that the islet was populated at the begin- ning of the 4th or 3rd century BC (Kršinić-Šove 1971, Solarić and Solarić 2009). During the last six centuries or so around six hundred people lived there and worked in thirty quar- ries (Dunda et al. 2003). Quarrying on the island continued until the late 1950s and cessation of it coincides with the de- population of the island (Galić et al. 1999). The population in the middle of the 20th century was almost 200; numbers then gradually diminished and nowadays there are only a few per- manent inhabitants. Nowadays, it is very popular as a tourist destination in the summer time having a population in ex- cess of about 200 people in a very small settlement (the vil- lage of Vrnik). The modern village of Vrnik occupies the land between the quarry-face and the northern coast, an area pre- viously quarried away. Abandoned quarry workers' cottages cluster in the eastern part of the modern village. In the Mediterranean Basin the flora of small and very small islands has long been a subject of interest in relation both to basic floristic knowledge and also in order to assess the impact of land use on the land cover (Jasprica et al. 2015, and references therein). In the northern section of the Medi- terranean Sea, the Adriatic basin forms its most important part. The Adriatic Sea has over 1,300 islands and isles, mostly located along its eastern, Croatian, coast, which are consid- ered among the most diverse in the Mediterranean region. Generally, the Dalmatian coast could be also defined as a hotspot, but the data on its flora are still incomplete (Médail and Quézel 1997). An estimation using the species-area re- lationship analysis (SAR) for 106 Adriatic islands (Nikolić et al. 2008), shows that 1,807 plant taxa grow on the Croatian islands, providing a heritage of biodiversity that must be be- queathed to future generations as a ‘reservoir’ available for the processes of biological evolution and for their ecological value. However, there naturally remain islands and islets that have not yet been floristically and ecologically investigated. Generally, all islets in the Korčula Archipelago re- main completely botanically unknown, and only a few bo- tanical studies have been made of the rest of the islets (e.g. Bogdanović and Brullo 2015, Jasprica and Milović 2016). The aim of this study was to present results of investigations into the flora and vegetation of the islet of Vrnik. Our hypothesis was that vegetation cover on the islet is mostly the result of temporary natural factors. Study area The islet has an area of 0.281 km2 with a maximum length of 900 meters, a width of 450 m, a maximum altitude of 46 m and a distance from the island of Korčula of 100 m (Fig. 1). The predominant soil type is calcocambisol (Korolija et al. 1977). The coast is low and rocky and has a total length of 2.3 km. Sea depths around the islet are between 2 and 15 m. Quarrying activity was focused at the northern part of the islet (Fig. 2). A near continuous quarry face runs across this area for just over 500 m from midway along the north- east side of the islet to midway along its northwest side; a sec- ond quarry-face runs from this point down the western side of the islet for at least 250 m (Russell and Glicksman 2015). The climate of the islet is Mediterranean, with mild win- ters and hot summers. The reference thermo-pluviometric station is Korčula. The average annual air temperature is 16.8 °C, precipitation ranges from 1000 – 1250 mm yr–1 and there are 2,400 hours of sunshine a year (Krklec et al. 2011). Over- all the bioclimate of the area can be defined as lower meso- Mediterranean (sensu Rivas-Martínez et al. 2011, Jasprica and Milović 2016). The islet belongs, as a part of the island of Korčula, to the Important Plant Areas (IPAs) in Croatia (Jasprica 2010). In addition, the islet is part of the NATURA 2000 Europe- an Ecological Network of sites important for birds (site code HR1000036: Middle Dalmatian islands and the Pelješac peninsula; Official Gazette of the Republic of Croatia 2013b, 2015). Unfortunately, there are currently no plans for Natura 2000 network management of the islet. Fig. 2. Quarry-face on the northern side of the islet of Vrnik in the late 1950s. Materials and methods Flora The study was carried out from 2014 to 2016 in different seasons (early and late spring, early summer and autumn). Herbarium specimens are deposited in the herbarium col- lection of the Laboratory for Terrestrial Flora and Fauna of the University of Dubrovnik (www.imp-du.com). Collections were made only if ten or more individuals were present in a plant population. Coordinates were listed according to the Croatian Terrestrial Reference System 1996 (HTRS96) based on the European Terrestrial Reference System 1989 (ETRS89) with Geodetic Reference System 1980 (GRS80) level-ellip- JASPRICA N., DOLINA K., MILOVIĆ M. 128 ACTA BOT. CROAT. 77 (2), 2018 soid as a mathematical and physical approximation of Earth’s shape. Data on the surface area and perimeter of the islands were obtained from the Croatian Programme for the protection and use of small, both inhabited and uninhabited, islands and the surrounding sea (Ministry of the Sea, Transport and In- frastructure 2007). The highest altitude was determined using topographic maps to the scale 1:25000 (TK25, TOPO HR). In the list (On-line Suppl. Tab. 1), species are given in al- phabetical order. For each taxon, life form and chorological element are reported. The life form follows the Raunkiaer system (Raunkiaer 1934) as proposed by Pignatti (1982). Re- garding chorological form, reference was made to Jasprica et al. (2016a), Milović et al. (2016) and references therein. Tax- onomic nomenclature follows the Flora Croatica Database (Nikolić 2017). were separated into associations/stands on the basis of the di- agnostic and/or dominant species, in line with the traditional syntaxonomic system of the communities. The syntaxonom- ical system (the EuroVegChecklist) proposed by Mucina et al. (2016), and followed by Škvorc et al. (2017) was applied. Classification of the vegetation units distinguished into habi- tat types of Annex I of the Habitats Directive 92/43/EEC was made according to the List of NATURA 2000 habitats de- clared by the Croatian Government (European Commission 1992, 2013; Official Gazette of the Republic of Croatia 2014). Priority habitats are denoted by an asterisk (*) as shown in the syntaxonomic scheme. Results Flora Two hundred and fifty-one (251) vascular plant taxa (spe- cies and infraspecific units) were recorded on the islet of Vrnik (On-line Suppl. Tab. 1). Altogether, 70 families and 186 gen- era were noted. Among them, the families most represented were: Poaceae (30 taxa, 12%), Fabaceae (28, 11.2%), Cichoria- ceae (16, 6.4%), Asteraceae (13, 5.2%), Lamiaceae (11, 4.4%), Rubiaceae and Caryophyllaceae (eight taxa in each, 3.2%), and Apiaceae, Brassicaceae, Euphorbiaceae and Ranunculaceae (six taxa in each, 2.4%). Four taxa can be considered as endemic: Anthyllis vulneraria ssp. weldeniana, Limonium dictyophorum, Lolium subulatum and Seseli tomentosum. From the Croatian Red List, Papaver hybridum is con- sidered to be a Critically Endangered (CR) taxon. Endan- gered taxa (EN) were Carex extensa, Delphinium staphisagria and Glaucium flavum, while Ophrys sphegodes, Orchis simia, Parapholis incurva and Salsola soda have been classified as Vulnerable (VU). In addition, nine taxa (Adiantum capillus- veneris, Anacamptis pyramidalis, Cyclamen repandum, Ely- mus pycnanthus, Limonium dictyophorum, Matthiola incana, Seseli tomentosum, Sternbergia lutea and Teucrium fruticans) were classified as Near Threatened (NT). Ruscus aculeatus was found to be of Least Concern (LC). Seven taxa (Brachy- podium phoenicoides, Ecballium elaterium, Echinaria capitata, Lolium subulatum, Raphanus raphanistrum ssp. landra, Trifo- lium echinatum and Posidonia oceanica) have been classified as Data Deficient (DD). In total, 16 taxa were Strictly Protected (SPT) by Cro- atian law: Anacamptis pyramidalis, Anthyllis vulneraria ssp. weldeniana, Carex extensa, Delphinium staphisagria, Echinar- ia capitata, Gladiolus illyricus, Glaucium flavum, Limonium dictyophorum, Lolium subulatum, Ophrys sphegodes, Orchis simia, Papaver hybridum, Parapholis incurva, Posidonia oce- anica, Salsola soda and Seseli tomentosum. Among the recorded taxa, Ailanthus altissima, Carpobro- tus acinaciformis, Conyza canadensis and C. sumatrensis are considered to be invasive (IAS). Carpobrotus acinaciformis covers larger areas on the northern slopes of the islet. The analysis of plant life forms showed that the Vrnik flora is dominated by therophytes (35.4%) and hemicryptophytes (23.9%), respectively (Tab. 1). Tab. 1. Life-form spectra on the islet of Vrnik. Life forms No. (%) Therophytes (T) 89 (35.4) Hemicryptophytes (H) 60 (23.9) Phanerophytes (P) 49 (19.5) Chamaephytes (Ch) 27 (10.8) Geophytes (G) 25 (10.0) Hydrophytes (Hy) 1 (0.4) Total taxa 251 (100.0) Taxa listed in the Red Book of Vascular Flora of Croatia (Nikolić and Topić 2005, Nikolić 2017) are marked with their corresponding IUCN status (IUCN 2016). Taxa considered to be endemic are denoted according to Nikolić et al. (2015). In addition, strictly protected taxa (SPT) as defined by Cro- atian law are also denoted (Official Gazette of the Republic of Croatia 2013a, c). Any invasive alien taxa (IAS) have been defined according to Nikolić et al. (2014) and Nikolić (2017). Taxa were determined using the standard determination keys, books and guides: Bonnier (1911–1935), Fiori (1923– 1929), Hayek (1924–1933), Hegi (1936–1987), Horvatić and Trinajstić (1967–1981), Tutin et al. (1968–1980, 1993), Ja- vorka and Csapody (1975), Trinajstić (1975–1986), Pignatti (1982), Delforge (1995, 2006), etc. Vegetation Vegetation was studied in accordance with the principles of the Braun-Blanquet approach (Braun-Blanquet 1964), adopting the International Code of Phytosociological No- menclature (Weber et al. 2000, see also Dengler et al. 2008). Altogether, 26 phytosociological relevés were collected on the islets. The plot size used to sample vegetation was established so as to represent the full floristic composition, depending on plant density and homogeneity of vegetation cover. Geo- graphical coordinates using the Croatian Terrestrial Refer- ence System 1996 (HTRS96), elevation above sea level, aspect and slope inclination were noted for each relevé. The relevés FLORA AND VEGETATION OF THE MEDITERRANEAN ISLET ACTA BOT. CROAT. 77 (2), 2018 129 Limonietum anfracti Ilijanić and S. Hećimović 1982 he- lichrysetosum italici Jasprica 2015 [habitat code 1240 – Veg- etated sea cliffs of the Mediterranean coasts with endemic Limonium spp.] SAGINETEA MARITIMAE Westhoff et al. 1962 Parapholis incurva community [habitat code 1310 – Sali- cornia and other annuals colonising mud and sand] CYMBALARIO-PARIETARIETEA DIFFUSAE Oberd. 1969 TORTULO-CYMBALARIETALIA Segal 1969 Galio valantiae-Parietarion judaicae Rivas-Mart. ex O. de Bolòs 1967 Oxalido-Parietarietum judaicae (Br.-Bl. 1952) Segal 1969 Cymbalario-Asplenion Segal 1969 Linario cymbalariae-Parietarietum ramiflorae Pignatti 1952 (=Cymbalarietum muralis Görs 1966) [habitat code 8210 – Cal- careous rocky slopes with chasmophyic vegetation] LYGEO SPARTI-STIPETEA TENACISSIMAE Rivas- Mart. 1978 nom. conserv. propos. (=THERO-BRACHYPO- DIETEA RAMOSI Br.-Bl. in Br.-Bl. et al. 1947) CYMBOPOGONO -BRACHYPODIETALIA RAMOSI Horvatić 1963 Cymbopogono-Brachypodion ramosi Horvatić 1963 Piptatheretum miliaceae Horvatić (1956) 1958 [habitat code 6220* – Pseudosteppe with grasses and annuals Thero- Brachypodietea] PAPAVERETEA RHOEADIS S. Brullo et al. 2001 nom. conserv. propos. APERETALIA SPICAE-VENTI J.Tx. et Tx. in Malato-Be- liz et al. 1960 nom. conserv. propos. Cynodon dactylon community CHENOPODIETEA Br.-Bl. in Br.-Bl. et al. 1952 BROMETALIA RUBENTI-TECTORUM (Rivas Goday et Rivas-Mart. 1973) Rivas-Mart. et Izco 1977 nom. conserv. propos. Hordeion murini Br.-Bl. in Br.-Bl. et al. 1936 Hordeetum leporini Br.-Bl. 1936 QUERCETEA ILICIS Br.-Bl. ex A. Bolòs et O. de Bolòs in A. Bolòs y Vayreda 1950 PINETALIA HALEPENSIS Biondi, Blasi, Galdenzi, Pesa- resi et Vagge in Biondi et al. 2014 Pistacio lentisci-Pinion halepensis Biondi, Blasi, Galden- zi, Pesaresi et Vagge in Biondi et al. 2014 Pistacio lentisci-Pinetum halepensis De Marco, Veri et Ca- neva 1984 Querco ilicis-Pinetum halepensis Loisel 1971 [habitat code 9540 – Mediterranean pine forests with endemic Mesogean pines] PISTACIO LENTISCI-RHAMNETALIA ALATERNI Ri- vas-Mart. 1975 The Mediterranean floral element (60.6 %), followed by a considerable proportion of South European plants (15.5%) and Cosmopolitans (13.1%), dominated on the islet (Tab. 2). Tab. 2. Floral elements on the islet of Vrnik. Floral elements No. (%) Mediterranean (MED) 152 (60.6) South European (SEU) 39 (15.5) Cosmopolitan (WISP) 33 (13.1) Eurasian (EUAS) 13 (5.2) European (EURO) 6 (2.4) Cultivated and adventive plants (CUAD) 6 (2.4) Illyrian-Balkanic (ILBA) 1 (0.4) Southeast European (SEEU) 1 (0.4) Total taxa 251 (100.0) Vegetation In all, 11 plant associations, one subassocation and two stands within 10 vegetation classes were identified on the is- let. These communities are described below and discussed in the same order of the syntaxonomical scheme. Their syntaxonomic scheme is as follows (corresponding NATURA 2000 habitat codes are added in square brackets): PHRAGMITO-MAGNOCARICETEA Klika in Klika et Novák 1941 OENANTHETALIA AQUATICAE Hejný ex Balátová- Tuláčková et al. 1993 Eleocharito palustris-Sagittarion sagittifoliae Passarge 1964 Eleocharitetum palustris Savič 1926 ZOSTERETEA Pignatti 1953 POSIDONIETALIA OCEANICAE Den Hartog ex Mu- cina in Mucina et al. 2016 Posidonion oceanicae Br.-Bl. ex Molinier 1960 Posidonietum oceanicae (Funk 1927) Molinier 1958 [habi- tat code 1120* – Posidonia beds (Posidonion oceanicae)] CAKILETEA MARITIMAE Tx. et Preising in Tx. ex Oberd. 1952 THERO-ATRIPLICETALIA Pignatti 1953 Euphorbion peplidis Tx. ex Oberd. 1952 Euphorbio pineae-Glaucietum flavi Horvatić 1934 [habi- tat code 1210 – Annual vegetation of drift lines (Euphorbion peplidis)] CRITHMO-STATICETEA Br.-Bl. in Br.-Bl. et al. 1952 CRITHMO-STATICETALIA Molinier 1934 Limonion anfracti-cancellati (Horvatić 1934) Mucina in Mucina et al. 2016 JASPRICA N., DOLINA K., MILOVIĆ M. 130 ACTA BOT. CROAT. 77 (2), 2018 Oleo-Ceratonion siliquae Br.-Bl. ex Guinochet et Dr- ouineau 1944 Myrto communis-Pistacietum lentisci (Molinier 1954) Ri- vas-Mart. 1975 Erico manipuliflorae-Calicotometum infestae Horvatić 1958 [habitat code 9320 – Olea and Ceratonia forests] Short description of the associations and stands Eleocharitetum palustris Savič 1926. This monospecific or species-poor community develops in small standing water bodies, e.g. shallow depressions with water depths of 10–50 cm, which are fed by rainfall (Fig. 3). These habitats remain slightly wet in summer, but in some years the community can also survive periods of soil desiccation (e.g. Šumberová 2011). In the case of Vrnik, Eleocharis palustris (5) formed stands with the co-occurrence of Chara vulgaris (1) [Rel.: 15.6.2016., HTRS96 X=554620, Y=4755266, plot size 16 m2, altitude 40 m, vegetation cover 100%]. The association has also been reported for the Continental and Mediterranean regions of Croatia (Stančić 2008), other parts of the Balkans (Tzonev et al. 2009, Šilc and Čarni 2012, Laketić et al. 2013), and also in Central and south Europe (Šumberová 2011, Lan- ducci et al. 2013). Posidonietum oceanicae (Funk 1927) Molinier 1958. It oc- curs on various stations around the islet and develops on the moving seabed in depths between 1 and 15 m, and represents the breeding site for many species. Extensive descriptions of the structure and the functioning of Posidonia beds have been produced by Buia et al. (2000) and Den Hartog (2003). Euphorbio pineae-Glaucietum flavi Horvatić 1934 (On- line Suppl. Tab. 2, rels. 1–2). On the islet of Vrnik this is rep- resented by the therophytic halo-nitrophilous vegetation that has colonised the sandy pebbled beach, rich in organic mat- ter. The association is very common along the whole eastern Adriatic in the mid-littoral zone on sandy and gravel sub- strates (Horvatić 1963, Jasprica et al. 2016b). Limonietum anfracti Ilijanić and S. Hećimović 1982 he- lichrysetosum italici Jasprica 2015 (On-line Suppl. Tab. 2, rels. 3–7). The rocky shores are home to the Limonietum anfracti plant association, characterised by Limonium dictyophorum, a species endemic to the southern coast of the eastern Adri- atic (Nikolić et al. 2015), which forms dense low-spreading formations that colonise the cracks in the rocks. Parapholis incurva community. [Rel.: 15.6.2016., HTRS96 X=554795, Y=4755453, plot size 6 m2, altitude 1 m, vegeta- tion cover 70%]. This therophytic community is rare on the islet and it occurs within the village at sunny sites at the edge of paths. Soils are very dry, usually with a sand admixture. In the case of Vrnik, the floristic composition was as follows: Parapholis incurva (4), Dorycnium hirsutum (+), Cakile ma- ritima (+), Silene vulgaris ssp. angustifolia (1), Helichrysum italicum (+), Pinus halepensis (r), Anagalis arvensis (+), Ai- lanthus altissima (r). On the islet wall vegetation was only found at a few sites within the village. The association Oxalido-Parietarietum ju- daicae (On-line Suppl. Tab. 3, rels. 1–3) is a sciaphilous and nitrophilous association mainly occurring on N-facing or shady walls (Brullo and Guarino 1998). In its typical aspect it forms a belt in the lower part of the wall. The presence of Scaligeria cretica (=S. napiformis), a rare taxon of Croatian flora, expands our knowledge of its chorology on the east- ern Adriatic (Skelin et al. 2014). In the Linario cymbalariae- Parietarietum ramiflorae (On-line Suppl. Tab. 3, rel. 4), Cym- balaria muralis contributed significantly. Additionally, quarry faces are covered with Inula verbascifolia, Adianthum capillus- veneris, Pinus halepensis, Cupressus horizontalis, Calamintha nepetoides and Hedera helix (On-line Suppl. 3, rels. 5–6). The thermophilic chasmophytic vegetation of the Asplenietea tri- chomanis class, at least in part, is not developed on the islet. Piptatheretum miliaceae Horvatić (1956) 1958. [Rel.: 15.6.2016., HTRS96 X=554334, 4755425, plot size 8 m2, alti- tude 1 m, vegetation cover 100%]. This association is rare and mostly localized on sites within the village, and sporadically on deep and wet soil within Aleppo pine wood. The floristic composition on the islet was as follows: Pipatherum miliace- um (5), Verbascum sinuatum (1), Calamintha nepetoides (+), Conyza sumatrensis (+), Lagurus ovatus (+), Lavatera arborea (+), Asphodelus fistulosus (+), Parietaria judaica (+), Euphor- bia peplus (+), Rubia peregrina (+), Ailanthus altissima (+), Hedera helix (+), Bituminaria bituminosa (+), Sonchus asper ssp. glaucescens (+), Geranium sp. (+). Cynodon dactylon community. [Rel.: 15.6.2016., HTRS96 X=554367, 4755533, plot size 12 m2, altitude 1 m, vegetation cover 90%]. It occurs at trampled sites with sandy dry soils in the village. The floristic composition on the islet was as fol- lows: Cynodon dactylon (5), Hordeum murinum ssp. lepori- num (1), Silene vulgaris ssp. angustifolia (1), Melilotus officina- lis (1), Trifolium scabrum (+), Galium lucidum (+), Medicago truncatula (+), Anthemis arvensis (+), Arenaria leptoclados (+), Desmazeria rigida (+), Lophochloa cristata (+), Lagurus ovatus (+), Lolium perenne (+), Malva sylvestris (+), Spergu- laria salina (+). Hordeetum leporini Br.-Bl. 1936. This nitrophilous veg- etation occurs in sunny sites at the edge of paths or on aban-Fig. 3. Eleocharitetum palustris Savič 1926. FLORA AND VEGETATION OF THE MEDITERRANEAN ISLET ACTA BOT. CROAT. 77 (2), 2018 131 doned land where the soil formation is embryonic and hu- man disturbance is a significant factor. It is characterized by species of predominantly annual spring development. The floristic composition on the islet [Rel.: 26.4.2014., HTRS96 X=554369, Y=4755536, plot size 25 m2, altitude 1 m, veg- etation cover 90%] was as follows: Hordeum murinum ssp. leporinum (2), Malva sylvestris (+), Plantago coronopus (1), Anthemis arvensis (1), Bromus madritensis (+), Bromus rac- emosus (+), Carduus pycnocephalus (+), Crepis rubra (+), Eu- phorbia helioscopia (+), Galium aparine (+), Geranium molle (+), Lagurus ovatus (+), Medicago polymorpha (+), Melilo- tus officinalis (3), Mercurialis annua (+), Rhagadiolus stella- tus (+), Setaria viridis (+), Sonchus oleraceus (+), Trifolium tomentosum (+). The association has already been noted for ruderal sites of the eastern and western Adriatic coasts and also reported for the W. Mediterranean (Jasprica et al. 2016b, and references therein). Among the wood vegetation, Querco-Pinetum halepen- sis occupies the majority of the area of the islet of Vrnik with a vegetation cover of 90–100%. It occurs exclusively on the southern slopes. It has value from an aesthetic and ecologi- cal point of view (On-line Suppl. Tab. 4, rels. 9–13). Quercus ilex is developed in the brush layer and Pinus halepensis is the dominant taxon. By contrast, Pistacio-Pinetum halepen- sis develops on the eastern and south-eastern part of the is- let, where Pistacia lentiscus contributes significantly (On-line Suppl. Tab. 4, rels. 5–8). Among macchia, the Myrto-Pista- cietum association has developed as low (mostly between 1 and 1.5 m) and dense shrub formations, and forms a strip be- tween halophytic vegetation and the islet’s central area (On- line Suppl. Tab. 4, rels. 1–3). The Erico-Calicotometum, with a height of 3–4 m, occupies a very limited surface area on the southern side of the islet, and has the greatest number of taxa (On-line Suppl. Tab. 4, rel. 4). In general most of the com- panions of these associations were treated as characteristic species of the Festuco-Brometea and Lygeo-Stipetea classes. Among companions, Brachypodium retusum has the high- est frequency. Discussion The predominance of the Poaceae, Cichoriaceae, Asterace- ae and Fabaceae families, a clear dominance of therophytes in the life-form spectrum and the Mediterraneans in the choro- logical spectrum include the islet in the Mediterranean con- text. The presence of the endemic taxa and those occurring in the national Red List, including strictly protected flora, confirm the peculiarity of the surveyed area from the phyto- geographic point of view (Nikolić et al. 2008). The islet investigated showed a relatively low variety of vascular plant taxa. This is, at least partly, in accordance with the findings of Pandža and Milović (2015) for some uninhab- ited eastern Adriatic islets with surface areas of less than one km2. However, the differences in the floristic diversity among the islets are very difficult to evaluate due to variations in the topography and the degree of human presence on the islets (Pasta et al. 2014, Jasprica et al. 2016b, and references there- in). In general, this is not a rare pattern on such islets, which often represent ‘unbalanced biota’ (Jasprica et al. 2015). The currently low number of alien species to be found in the islet may be related to the low level of human activity. However, habitat modification or space occupation by Carpo- brotus acinaciformis might represent a threat (Brundu 2013, Celesti-Grapow et al. 2016). The risk of invasion may increase if more species are directly introduced to the islet, and if an- thropogenic disturbance and a changing climate make con- ditions more favourable for alien species (Lloret et al. 2005, Pretto et al. 2012, Cardona Pons et al. 2013, Valaoras 2014). Nevertheless, quarrying operations caused ecosystem disturbance and profound modifications of the substratum and the topographical profile of the islet (Khater and Arn- aud 2007). In our case, fragmentation of the forest vegeta- tion was observed. Parts of the open quarry-faces have be- come overgrown during the last few decades (Fig. 4), and, in general, on such heavily disturbed areas, spontaneous colo- nization is slow (Whisenant et al. 1995). This survey revealed the presence on quarry cliffs of ‘true’ rupicolous species (e.g. Campanula pyramidalis, etc.), which have been recorded for Fig. 4. Vegetation cover on the islet during the Second World War (A) and in 2016 (B). JASPRICA N., DOLINA K., MILOVIĆ M. 132 ACTA BOT. CROAT. 77 (2), 2018 the neighbouring islet (Jasprica and Milović 2016). Generally, the scientific literature lacks suitable references highlighting the ecological value of abandoned quarries. Arnal (1993) and Vela (2002) confirmed the presence in quarries of particular plant species, some of them being exclusive to this type of ecosystem and some rare and/or protected species spotted in abandoned quarries have been reported beyond their natural distribution area. These were not found in our case. Regarding vegetation, the islet shows a relatively low va- riety of terrestrial plant associations, and most of these are fragmentary. However, some of them (e.g. Parapholis incurva and Cynodon dactylon communities) are little known on the eastern Adriatic and further comparable research is required for a more complete understanding of these stands. In conclusion, we confirm our hypothesis that the vegeta- tion cover on the islet is in general a result of temporary nat- ural factors. However, the environmental impact from past quarrying activities is observable. 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Syntaxa quoted in the text and tables (in alphabetical order), but not in scheme Adiantetea Br.-Bl. et al. 1952 Ammophiletea Br.-Bl. et Tx. ex Westhoff et al. 1946 Artemisietea vulgaris Lohmeyer et al. in Tx. ex von Rochow 1951 Asplenietea trichomanis (Br.-Bl. in Meier et Br.-Bl. 1934) Oberd. 1977 Carpino-Fagetea sylvaticae Jakucs ex Passarge 1968 Epilobietea angustifolii Tx. et Preising ex von Rochow 1951 Festuco-Brometea Br.-Bl. et Tx. ex Soo 1947 Isoëto-Nanojuncetea Br.-Bl. et Tx. in Br.-Bl. et al. 1952 Juncetea maritimi Br.-Bl. in Br.-Bl. et al. 1952 Ononido-Rosmarinetea Br.-Bl. in A. Bolòs y Vayreda 1950 Quercetea pubescentis Doing-Kraft ex Scamoni et Passarge 1959 Salicornietea fruticosae Br.-Bl. et Tx. ex A. Bolòs y Vayreda et O. de Bolòs in A. Bolòs y Vayreda 1950