The new association Pimpinello lithophilae-Centaureetum lovricii (Crithmo-Staticetea) from the island of Vis (southern Croatia) Jasprica Nenad nenad.jasprica@unidu.hr Terzi Massimo massimo.terzi@ibbr.cnr.it University of Dubrovnik, Institute for Marine and Coastal Research, P.O. Box 83, HR-20000 Dubrovnik, Croatia Croatia Institute of Bioscience and Bioresources, National Research Council of Italy, via Amendola 165/A, IT-70126, Bari, Italy Italy 11 01 2023 25 09 2023 2509202382 <bold id="_bold-13">Introduction</bold>

The Vis Archipelago is located off the Eastern Adriatic (central Dalmatian) coast, in Croatia. The archipelago shows an exceptional concentration of endemic and rare plant species (e.g., Centaurea spp. and Limonium spp.) (Nikolić et al. 2015). Many of them inhabit halophytic and chasmophytic coastal and subcoastal habitats within rare plant communities (Terzi et al. 2020).

In Croatia, according to the European syntaxonomic framework of the EuroVegChecklist (EVC: Mucina et al. 2016), the halophilous coastal vegetation is included in the order Crithmo-Staticetalia whereas the halotolerant belt is classified in the order Helichrysetalia italici (Škvorc et al. 2017). Both orders belong to the Crithmo-Staticetea class. Although Škvorc et al. (2017) were the first to recognize the occurrence of Helichrysetalia italici in Croatia, this order was widely described and documented for the first time for the eastern Adriatic by Terzi et al. (2020).

Helichrysetalia italici occurs between coastal vegetation under the direct influence of sea-borne salt spray and a vegetation belt notably less influenced by salt spray. In the island of Vis, within the order Helichrysetalia italici Terzi et al. (2020) reported two alliances (1) Anthyllidion barbae-jovis, with a Central Mediterranean distribution, and (2) Capparo orientalis-Aurinion leucadeae - an endemic alliance of the central Adriatic islands (Croatia) and the Tremiti (Italy).

The alliance Capparo-Aurinion, alongside four associations described from neighbouring islets in the Vis Archipelago and the Tremiti as well, includes the stenoendemic association Pimpinello lithophilae-Centaureetum issaeae Terzi, Bogdanović, D'Amico et Jasprica 2020 from the island of Vis. This association was, however, invalidly described because one of the name-giving taxon, Centaurea issaea Lovrić, had not been validly published at that time (Art. 3 l of the ICPN, International Code of Phytosociological Nomenclature, Theurillat et al. 2021). In fact, according to Bogdanović et al. (2022), Centaurea issaea is a nomen nudum. Therefore, these authors described the new species C. lovricii. Consequently, it is, the new association Pimpinello lithophilae-Centaureetum lovricii that is described here.

<bold id="_bold-16">Materials and methods</bold>

This study was carried out according to the Braun-Blanquet approach (Westhoff and van der Maarel 1980). In the type relevé of the new association, the extended 9-point Braun-Blanquet cover-abundance scale was used, with a subdivision of symbol 2 into 2m, 2a and 2b (see Westhoff and van der Maarel 1980 and references therein). Nomenclatural decisions follow the fourth edition of the ICPN (Theurillat et al. 2021). Taxonomic nomenclature follows Flora Croatica Database (Nikolić 2023) except for Limonium issaeumand Centaurea lovricii, the nomenclature of which follows the revisions carried out by Bogdanović and Brullo (2015), and Bogdanović et al. (2022), respectively. Syntaxonomic nomenclature follows the Euro VegChecklist (EVC: Mucina et al. 2016). For complete description of the alliance Capparo-Aurinion and belonging tables, see Terzi et al. (2020).

 <bold id="_bold-17">Results and discussion</bold>

Syntaxonomic scheme:

Class: Crithmo-Staticetea Br.-Bl. in Br.-Bl. et al. 1952

Order: Helichrysetalia italici Biondi et Géhu in Géhu et Biondi 1994

Alliance:Capparo orientalis-Aurinion leucadeae Lovrić ex Terzi, Bogdanović, D'Amico et Jasprica 2020

Association: Pimpinello lithophilae-Centaureetum lovricii Jasprica et Terzi ass. nov.

Holotypus: Relevé no. 50 of Supplement S3 inTerzi et al. (2020), from the island of Vis. Plot size: 20 m2; coordinates (WGS84): latitude 43°04'28", longitude 16°06'33"; altitude 30 m a.s.l., aspect: 360°; slope 60°; vegetation cover 40%; date: 30 May 2018. List of taxa: Brachypodium retusum, 2m; Brassica incana, 2m; Centaurea lovricii, 2a; Coronilla valentina subsp. valentina, +; Crithmum maritimum, +; Desmazeria rigida, +; Dorycnium hirsutum, r; Erica manipuliflora, +; Helichrysum italicum subsp. italicum, 2m; Inula verbascifolia, 2a; Juniperus phoenicea, +; Limonium issaeum, 1; Pimpinella tragium subsp. lithophila, 2m; Reichardia picroides, +; Silene vulgaris subsp. angustifolia, +; Valantia muralis, 1. Name-giving taxa: Pimpinella tragium Vill. subsp. lithophila (Schischk.) Tutin and Centaurea lovricii Bogdanović, Boršić, Ljubičić, Brullo et Giusso.

Distribution records: The stands occur along the northern coast between Dragodid Bay and Oključina Bay, the island of Vis (Fig. 1). The association is localized in a narrow coastal belt of ca. 0.5 km2.

Fig. 1. Pimpinello lithophilae-Centaureetum lovricii, ass. nova. A – the habitat type, B – Pimpinella tragium subsp. lithophila, C – Centaurea lovricii, D – detail of the association with C. lovricii and Brassica incana. (Photo: N. Jasprica; the island of Vis, May 30, 2018).

Ecology: It grows on sea facing cliffs constituted of Triassic dolomites at 10–100 m a.s.l. The association Pimpinello lithophilae-Centaureetum lovricii is characterized by the steno-endemic Centaurea lovricii and differentiated by Brassica incana and Pimpinella tragium subsp. lithophila. The latter is found in almost all countries of the northern Mediterranean basin, while the distribution area of Brassica incana includes the western Balkans and Italy (Euro+Med 2006-2023). However, those two taxa are rare along the Dalmatian coast (Bogdanović and Ruščić 2011, Nikolić et al. 2015, Nikolić 2023) and therefore are selected as differential taxa of the new association.

Aurinia leucadea and Capparis orientalis were also included among the character-taxa of Capparo-Aurinion. The association includes narrow endemic taxa (e.g., Centaurea lovricii, Campanula teutana, Limonium issaeum) together with some diagnostic taxa of Centaureo-Campanuletalia (Inula verbascifolia, Pimpinella tragium subsp. lithophila, Sesleria tenuifolia) and some others of Crithmo-Staticetea / Helichrysetalia italici (Crithmum maritimum, Helichrysum italicum, Allium commutatum).

Conservation status: According to Bogdanović et al. (2022), the population of C. lovricii is estimated as Vulnerable (VU D1) (sensu IUCN 2022). However, it grows on very steep and quite inaccessible habitats, which makes the population and plant association unthreatened by any human disturbance. The rarity of this taxon and its associated plant community necessitates the implementation of a comprehensive conservation strategy.

The association name Pimpinello lithophilae-Centaureetum issaeaeTerzi, Bogdanović, D'Amico et Jasprica 2020 nom. inval. (Art. 3 l) was formed from the taxa names Pimpinella tragium subsp. lithophila and Centaurea issaea. Although at that time, the name Centaurea issaea Lovrić was in use in the Flora Croatica Database (accessed 1 October 2018, see Terzi et al. 2020), it is a nomen nudum for Centaurea lovricii. Therefore, the name Pimpinello lithophilae-Centaureetum issaeae cannot be validated and is replaced here by Pimpinello lithophilae-Centaureetum lovricii. The relevés originally ascribed to the Pimpinello lithophilae-Centaureetum issaeae by Terzi et al. (2020: relevés 48-54 of Supplement S3) belong to the original diagnosis of the new association.

 <bold id="_bold-23">Acknowledgments</bold>

We thank Salvatore Brullo and an anonymous reviewer for their valuable comments and suggestions.

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