Genus Aristida L. is one of the exotic grasses in European flora. It belongs to subfamily Aristidoideae, which consists of three genera: Aristida L., Stipagrostis Nees and Sartidia De Winter, being easily recognisable by one-flowered spikelets, with 3-awned lemmas, with involute margins, a sharp pointed callus, and a line of hairs for a ligule (Cerros Tlatilpa et al. 2011). So far, Stipagrostis and Sartidia have not been reported in Europe, while the genus Aristida has been noted as having two representatives: A. adscensionis L. and A. oligantha Michx. (Euro+Med 2006, Rakaj and Pagad 2020). The first has been recorded in Spain, Italy, Greece (Euro+Med 2006), Belgium (Desmet et al. 2020) and France (Thevenot et al. 2020), while the second was recently reported in central part of Albania (Rakaj and Pagad 2020).
Within its native area of distribution, which includes North America the Aristida oligantha grows on waste or bare ground, old fields and dry hills (Allred 1986). It is considered an extremely aggressive weed species, which is rather dangerous for cattle, since its awns and sharp callus cause injuries to the mouth, nostrils, and eyes. It disperses in two ways, by wind or by attachment to passing animals thanks to its retrorsely- barded, sharp callus (Owensby and Launchbaugh 1977).
Aim of this paper is to alert on newly discovered alien species Aristida oligantha, to present the new records, as well as species composition and structure of Aristida oligantha plant community.
Material and methods
The collected plant material was deposited in the Herbarium Collection at the University of Montenegro, Podgorica, Montenegro (TGU), under the voucher number: TGU 1570528. The specimens were identified according to Allred (1986).
Phytosiociological relevés were recorded according to the method of Braun-Blanquet (1964), stored in a Tubroveg (Hennekens and Schaminée 2001) and incorporated into the vegetation database of Montenegro (EU-ME-001, http://www.givd.info/ID/EU-ME-001). The nomenclature of the taxa follows the Euro+Med (2006).
Results and discussion
Aristida oligantha (Fig. 1) was recorded in full bloom during the autumn field survey at sandy beach of Velika plaža in town of Ulcinj (Montenegro), just along the narrow road that passes through the hinterland. The plant builds almost monodominant stands in rather anthropogenized but poorly trampled sites, at which Brachypodietalia dune grasslands with annuals (Annex I habitat type, code 2240) dominate during the spring. From the roadside, Aristida stands are mainly connected with a narrow line of trampled vegetation dominated by Cynodon dactylon, and on the opposite side there is either forest vegetation of planted maritime pines or the association Eriantho-Schoenetum nigricantis (Pignatti 1953) Géhu in Géhu et al. 1984 within which Aristida colonizes the area between the tussocks of Schoenus nigricans (Tab. 1). The substrate is mostly sandy; exceptionally it is of crushed stones, which are used in this area as construction material for both car parks and paths. The total vegetation cover is mostly greater than 90%. In the Aristida oligantha community, the most frequent taxa were Cynodon dactylon, Erigeron canadensis (100%), Artemisia campestris, Tragus racemosus, Petrorhagia saxifrage and Verbascum sinuatum (77.7%, Tab. 1). The combination of late-summer and autumn species, notably Cynodon dactylon, Tragus racemosus and Euphorbia maculata define the syntaxonomic affiliation of this community to the alliance Eragrostion of the order Eragrostietalia and class Digitario sanguinalis-Eragrostietea minoris.
As new alien species in European flora the Aristida oligantha was recently reported in Albania (Rakaj and Pagad 2020). Actually, the species was recorded on riverside of the Osum River, near the town of Berat, South Albania, in 2013 (Marash Rakaj, pers. comm.). As sites are far apart introduction is probably independent. Nevertheless, due to the extremely close connection between the municipality of Ulcinj and Albania (trade, construction, tourism, or intense cross-border traffic), it is possible that species was imported from Albania. Introduction of species via construction material is a common means of spreading invasive species in Montenegro, as has been demonstrated by the spread of Ambrosia artemisiifolia (Stešević et al. 2014).
In autumn, in the hinterland of the Velika plaža beach, A. oligantha was recorded in monodominant stands – A. oligantha community (Tab. 1), as well as within association Eriantho-Schoenetum nigricantis, which represents the vegetation type equivalent of NATURA 2000 habitat 2190 Humid dune slack.
Taking into consideration the great invasive potential of this species, we propose further monitoring and assessment of its invasive status and the planning of eradication measures. In order to deepen our knowledge on the synecology of this species beyond the boundaries of its natural range, as well as to potentially describe any new association, it is necessary to do more detailed phytocenological research within the boundaries of the secondary range, which up to now covers only Albania and Montenegro in Europe.