Introduction
Due to coexistence in similar ecological environments, representatives of glassworts(Salicornia s.l. (incl. Sarcocornia A.J. Scott) and Arthrocnemum Moq.)have developed characteristic morphological traits, such as succulent, articulated and apparently leafless stems. Although they are easy to recognize, sometimes it is difficult to distinguish between species or even between the related genera. According to the literature sources (Kutleša and Lakušić 1964,Kaligarič and Škornik 2007,Kaligarič et al. 2008,Stešević and Caković 2013,Barina et al. 2018,Nikolić 2020), the following glasswort species/aggregates have been reported along the eastern Adriatic coast (SVN – Slovenia, HRV – Croatia, BIH – Bosnia and Hercegovina, MNE –- Montenegro, ALB – Albania): Arthrocaulon macrostachyum (SVN, HRV, BIH, ALB), Salicornia fruticosa (SVN, HRV, BIH, MNE, ALB), S. perennis (HRV, ALB), Salicornia europaea aggr. (SVN, HRV,MNE, ALB)and S. procumbens aggr. (SVN, HRV, ALB). To date, Arthrocaulon macrostachyum, Salicornia perennis and S. procumbens have not been included in the Checklist of Vascular Plants in Montenegro (Stešević and Caković 2013), while Salicornia perennis has not been recorded from BIH (Kutleša and Lakušić 1964), so the current results represent the first records in this part of the Adriatic coast.
The aim of this paper is to present new records of the glassworts A. macrostachyum, S. perennis and S. procumbens on the eastern Adriatic coast and to highlight their importance for nature conservation.
Material and methods
Field investigation was conducted along the eastern Adriatic coast in Montenegro and Bosnia and Herzegovina. The collected plant material was deposited in the Herbarium Collection of the University of Montenegro (TGU) and in the Herbarium of the Faculty of Forestry University of Banja Luka under the following voucher numbers: TGU 1570521 (Arthrocaulon macrostachyum), TGU 1570524 (Salicornia perennis), SFUNIBL 753/2017 (Salicornia perennis) and TGU 1644085 (Salicornia procumbens subsp. procumbens). Specimens were identified according to Kaligarič et al. (2008), Kadereit et al. (2012) and Piirainen et al. (2017). Phytosociological relevés were recorded according to the Braun-Blanquet method (1964) and included in the Vegetation Database of Montenegro (EU-ME-001, http://www.givd.info /ID /EU-ME-001). The nomenclature of the taxa given inTab. 1, and in the text follows Euro+Med (2006), except for the Arthrocaulon and Salicornia (Piirainen et al. 2017).
Results and discussion
Arthrocaulon macrostachyum (Moric.) Piirainen & G. Kadereit(syn. Salicornia macrostachya Moric., Arthrocnemum macrostachyum (Moric.) K. Koch, Salicornia virginica Forssk., Salicornia glauca Delile). The species is reported at several sites within Tivat Saline in Montenegro, at the edge of the front basin and on one of its islets. At all its microlocalities A. macrostachyum grows in association with Salicornia fruticosa L., but the cover of its individuals changes with the inundation period by the sea.Table 1 shows the four ecological microsites with A. macrostachyum from the slightly elevated site, which has the shortest exposure to direct seawater impact, to the rapid alternation of dry and wet phases, where it grows in a monodominant community (Tab. 1, rel. 1) to the longest flooded site, where it grows in the association Puccinellio festucaeformis-Sarcocornietum fruticosae (Braun-Blanquet 1928) Géhu 1976 (Tab. 1, rel. 4).
According to the IUCN (2012) criteria A. macrostachyum is considered Critically Endangered (CR) in Montenegro (Tab. 2).
Salicornia perennis Mill. (syn. Sarcocornia perennis (Mill.) A. J. Scott, Arthrocnemum perenne (Mill.) Moss). The species is found in Tivat Saline in Montenegro and in the Klek Peninsula in Bosnia and Herzegovina.
Salicornia perennis is more widespread in Tivat Saline than A. macrostachyum; it occurs not only in the slightly elevated and drier parts of the front basin, but also in the back basins, which are not exposed to the direct influence of seawater and are outside the tidal framework.Table 1 shows the phytosociological relevés with S. perennis recorded at different sites in Tivat Saline, starting with the wettest site, where S. fruticosa dominates, while S. perennis occurs only sporadically (rel. 5), through the transitional and less humid and flooded variants (rels. 6, 7), to the monodominant stands of S. perennis in the back basins, which are completely dry and out of the tidal range from May onwards (rels. 8, 9).
In Bosnia and Herzegovina, S. perennis is an extremely rare species that is found in a narrow zone of salt-sprayed rocky cliffs. It grows in flattened and sheltered parts of Plantagini-Limonietum cancellati Horvatić (1934) 1939, together with Limbarda crithmoides (L.) Dumort., Crithmum maritimum L., Limonium cancellatum (Bernh. ex Bertol.) Kuntze, Juncus acutus L., Sonchus maritimus L., Reichardia picroides (L.) Roth, etc.
According to the IUCN (2012) criteria, S. perennis is classified as Critically Endangered (CR) in both Montenegro and Bosnia and Herzegovina (Tab. 2).
Salicornia procumbens Sm. subsp. procumbens (syn. S. emericii Duval-Jouve, S. herbacea var. stricta G. Mey., S. procumbens var. stricta (G. Mey.) J. Duvign. & Lambinon in Lambinon & al., S. oliveri Moss, S. dolichostachya Moss, S. strictissima Gram, S. fragilis P.W. Ball & Tutin, S. lutescens P.W. Ball & Tutin, S. ramosissima var. vicensis J. Duvign., S. vicensis (J. Duvign.) J. Duvign., S. emericii var. peltii Géhu, Géhu-Franck & Caron, S. veneta Pignatti & Lausi, S. borysthenica Tzvelev) was found in Tivat Saline, both in the front and in the back basins as well as along the channels of the seawater drainage system on mudflats exposed to a regular tidal regime and nutrient flux, forming mostly immersed pioneer communities that are monospecific (Tab. 1, rel. 10) or of low species richness (Tab. 1, rels. 11-13). All relevés could be assigned to Salicornietum emerici O. Bolós ex Brullo et Furnari 1976.
According to the IUCN (2012) criteria, S. procumbens Sm. subsp. procumbens is classified as Critically Endangered (CR) in Montenegro (Tab. 2).
The morphological similarity of genera and species of certain halophytic succulents from the subfamily Salicornioideae, compounded by the lack of studies dealing with the diversity of this group, could be considered the main reasons why it took so long to identify and report A. macrostachyum, S. perennis and S. procumbens subsp. procumbens in the studied parts of the eastern Adriatic coast. Based on the experience gained in recent surveys at two studied sites in Montenegro and Bosnia and Herzegovina, further work on glasswort chorology all along the eastern Adriatic coast is recommended. Indeed, S. perennis is confirmed at both localities where only S. fruticosa is previously reported (Kutleša and Lakušić 1964,Janković and Stevanović 1983), while S. procumbens subsp. procumbens is reported at Tivat Saline where this annual glasswort has been treated as S. herbacea s.l. (Janković and Stevanović 1983). Inspection of a small number of existing digitised herbarium specimens from Croatia (using the platform of the Flora Croatica Database,Nikolić 2020), shows that the glasswort is still frequently confused and misidentified by many botanists (e.g. Arthrocaulon macrostachyum is frequently confused with Salicornia fruticosa).
Recent studies of annual glassworts (Kadereit et al. 2012,Kaligarič et al. 2008,Šajna et al. 2013) have shown that two annual species occur on the Adriatic coast: the tetraploid S. procumbens and the diploid S. perennans Willd.Along the inundation gradient, tetraploid species usually alternate with diploid. The vegetation belts containing these species are clearly distinguishable in late autumn when S. procumbens turns red and S. perennans remains dully green (Fanelli et al. 2015). During our field surveys we did not find S. perennans individuals, but since our transects did not cover the entire area of the saline, as well as the late autumn aspect, the reports of S. procumbens do not exclude the possibility that diploid S. perennans species also grow in the back basin of the saline. Thus, further investigation is required.
Based on the IUCN category assessment, we propose the newly reported glasswort species as candidates for the national list of protected plant species: Arthrocaulon macrostachyum, Salicornia procumbens subsp. procumbens and S. perennis in Montenegro and S. perennis in Bosnia and Herzegovina.