According to available literature sources, herbarium specimens as well as based on our own field data, in Kosovo there are four native Gymnadenia species. This study deals with: G. conopsea (L.) R. Br., G. frivaldii Hampe ex Griseb., G. nigra (L.) Rchb.f., and G. odoratissima (L.) Rich.

In this context, it is important to briefly discuss the taxonomic position of the species Gymnadenia nigra (L.) Rchb.f. Based on a study of this species by Teppner and Klein (1990), it was found that the natural distribution of G. nigra [homotypic synonym: Nigritella nigra (L.) Rchb. p.] is only in Scandinavia. Whereas in the Balkans G. nigra has been repeatedly erroneously reported and these specimens are in fact: Gymnadenia rhellicani (Teppner & E.Klein) Teppner & E.Klein [homotypic synonym: Nigritella rhellicani Teppner & E.Klein]. However, in the Euro+Med Plant Base (Euro + Med 2006+), on which we relied for the current study, such a conclusion is not yet supported. Consequently, we referred to the species as: G. nigra.

In total, 179 herbarium specimens (from the Herbarium of the Faculty of Natural Sciences, University of Prishtina) as well as private herbarium collection of F. Rexhepi (41 specimens) – (see Appendix 2 for details) were studied; the majority of these samples were collected by our team during the compilation of the Red Book of the vascular flora of the Republic of Kosovo (Millaku et al. 2013) between 2009 and 2013.

Due to the fact that during the work for the Red Book, the main focus were certain natural habitats that were rich in endemic plants, some regions of the country remained poorly sampled. To compensate for this, we have conducted twenty-five additional expeditions (between 2014 and 2020) to those poorly explored areas, in order to be more confident that the presented data will allow for general conclusions about the investigated genus in Kosovo.

Plant samples were finally identified by F. Millaku, using identification keys and other relevant literature sources (Diklić 1976; Gölz and Reinhard 1986; Tutin 2010).

To establish the distribution of Gymnadenia species in Kosovo, the literature was extensively examined (Lakušić and Grgić 1971; Diklić 1976; Rexhepi 1986; Krivošej 1997; Ranđelović et al. 1998; Millaku 1999; Stevanović ed. 1999; Micevski 2001; Bateman et al. 2006; Millaku ed. 2013; Ponert 2014; Djordjević et al. 2017). Determining the habitat type(s) for each species was done by comparing the habitat data where the species was recorded (from herbarium, literature and relevés) and finding the corresponding EUNIS habitat(s) according to Davies et al. (2004).

To gain an overview of where the studied Gymnadenia species grow, in terms of phytosociological plant communities and certain related ecological preferences, a total of 15 phytosociological relevés were made (Appendix 1). Based on our field experience as well as from general knowledge from plant ecology, efforts have been made to conduct appropriate and representative phytosociological relevés.

Standard principles and methods of the Zürich-Montpellier school (Braun-Blanquet 1964; Mueller-Dombois and Ellenberg 1974) were applied. Depending on the habitat type, plot sizes of 10 × 10 m and 5 × 10 m respectively were used. For each plot, a complete list of vascular plants was recorded, alongside with cover-abundance values on a five-degree scale (Braun-Blanquet 1932). For the nomenclature of plant taxa, the Euro+Med Plant Base (Euro+Med 2006+) was followed. Relevés were made at elevations ranging from 140 to 2501 m a.s.l.; four relevés were made on communities with G. conopsea, four relevés on communities with G. frivaldii, four relevés on communities with G. nigra and three relevés on communities with G. odoratissima.

Based on diagnostic species, efforts have been made to offer a syntaxonomical classification of these relevés up to the level of Alliance. For this purpose, Mucina et al. (2016), Rexhepi (1994) and Sarić and Kojić (1984) were followed.

Using data obtained from herbarium specimens, phytosociological relevés as well as from literature, we were able to analyze the following parameters: altitude preferences, a set of ecological values (nutrients, pH reaction, moisture, continentality, temperature and light) from accompanying species of plants, using Pignatti indicator values (Pignatti et al. 2005). EUNIS corresponding natural habitat types (Davies et al. 2004) were defined for each species. Additionally, data on the overall species richness (from relevés) and richness of endemic taxa were compared. All of the geographical distributional data were mapped to show the distribution of Gymnadenia species in Kosovo (Fig. 1). R software (R Core Team 2013) for statistical computing was used to do the comparative analysis and generate the graphs.

Figure 1. 

Known distribution of Gymnadenia species in Kosovo, based on herbarium specimens, as well as phytosociological relevés.

Based on the studied herbarium specimens, data collected from field surveys as well as literature sources, the presence of four Gymnadenia species is confirmed in a total of 88 different localities across Kosovo.

Within these localities, G. conopsea is clearly the most abundant species. Its presence has been confirmed in 60 localities and considering its ecological preferences, the species may have an even broader distribution across the country. Gymnadenia nigra is confirmed in 28 localities while G. frivaldii in 26 localities in Kosovo. Gymnadenia odoratissima is known so far to be present in only one locality in Kosovo (Appendix 2, Fig. 1).

Based on the obtained data from 15 phytosociological relevés, general data on each species preferences were evident. In terms of species distribution at different elevations, it was ascertained that the studied species show a narrow distributional preference (Fig. 2). It was established that G. conopsea had a preference for lower altitudes (<1000 m a.s.l.), though it had a wider distributional range. Gymnadenia frivaldii showed a greater preference for higher altitudes (>2100 m a.s.l.) and had a wider distribution range compared to G. nigra. As for G. odoratissima, this parameter shows a narrow median weight due to the fact that is known from a single locality at ~1700 m a.s.l.

Figure 2. 

Elevational distribution of four Gymnadenia species based on the study of 179 herbarium specimens, geographically located in Kosovo.

Concerning soil fertility and nutrients availability, it was established that all four Gymnadenia species communities grow on relatively poor soils, with an average value of 3. In this context, G. nigra communities can be distinguished with the lowest median weight compared to G. frivaldii and G. odoratissima that prefer slightly more nitrogen rich soils (Fig. 3, boxplot 1). As for soil pH reaction (Fig. 3, boxplot 2), it was observed that four studied species communities have a general preference for alkaline soils. Though six relevés were made on silicate soils, the occasionally deep, accumulated soil has a significant effect on reducing acidic influence of soil pH. In terms of soil moisture (Fig. 3, boxplot 3), it was established that plant communities of the four Gymnadenia species have a general preference for medium-wet soils, with G. frivaldii in particular, preferring wetter soils. With regard to climate-continentallity (C) values, it was clear that there are no oceanic species and the average (Fig. 3, boxplot 4) value of 5 is general for all studied species communities. The temperature (T) preferences (Fig. 3, boxplot 5) associate also with the community occurrences at respective elevations above sea level. But, additionally it relates to cold or warm habitats of Europe. In this context, apparent distinction in preferences has been observed namely between communities of G. conopsea (6) and G. nigra (3). As for light preferences (Fig. 3, boxplot 6), it was obvious that all studied communities have a clear preference for growing under full light, a preference particularly pronounced in the case of G. nigra.

Figure 3. 

Boxplots representing the ecological preferences for nutrients, pH reaction, moisture, continentality, temperature and light–for four studied Gymnadenia species, based on their phytosociological communities.

Regarding general species richness of all plant communities of the four respective species (Fig. 4, boxplot 1), communities of G. nigra and G. odoratissima were particularly distinguished by a large number of plant species. The other analyzed parameter, the number of endemic plant taxa per plant communities of a species, showed that plant communities of G. nigra (Fig. 4, boxplot 2) were particularly rich in endemics, while those of G. conopsea are notably poor. In this regard, G. frivaldii communities were rich in endemics too.

Figure 4. 

Comparative data on species richness and richness in endemic taxa beween the plant communities of four Gymnadenia species in Kosovo.

From 15 phytosociological relevés, after syntaxonomical analysis (relying on differential/characteristic species), it was noted that they belong to six different Classes (Appendix 1), with Elyno-Seslerietea Br.-Bl. 1948 (Class of vegetation that entails swards of Alpine and subalpine ranges of Europe) being the most abundant, in terms of relevé numbers.

Four relevés were made with G. conopsea communities. Three relevés fall into the alliance Chrysopogono-Danthonion calycinae Kojić 1959 (Dry grasslands on deep soils) and the other one into the alliance Trifolion resupinati Micevski 1957 (Vegetation of wet meadows).

Four relevés were made with G. frivaldii communities. As related with its typical natural habitats, the recorded plant communities (3) belonged to the alliance Narthecion scardici Horvat ex Lakušić 1968 (Relict moderately-rich fens of the Balkans) and the remaining one belongs to the alliance Cirsion appendiculati Horvat et al. 1937 (Tall-herb vegetation on acidic soils along mountain streams).

Additional four relevés were made with plant communities of G. nigra. They all fell into the alliance Seslerio juncifoliae-Caricion firmae Trinajstić 2005 (Alpine calcicolous sedge swards in wind-exposed habitats in the alpine belt of the Illyrian region and the Northern Dinarides). These four relevés were characterized by an exceptionally high number of associated endemic plant taxa (Fig. 4, boxplot 2).

Finally, a set of three relevés were made with plant communities where also G. odoratissima was growing. Due to a confined habitat (in Maja e Zezë, Sharri Mts.), it was quite difficult to record the relevé data. Two of these relevés, after analysis have shown affiliation to the alliance Cirsion appendiculati Horvat et al. 1937 (tall-herb vegetation on acidic soils along mountain streams and water springs at high altitudes), while the third one belonged to the alliance Epilobion angustifolii Oberd. 1957 (tall-herb perennial semi-natural vegetation on acidic soils of forest margins).

As expected, all four species of the genus Gymnadenia follow different distribution patterns in Kosovo. Gymnadenia conopsea is a widely distributed species in Europe. In south-eastern Europe, it is common in the Carpathians, Hungary, Romania, the Balkan Peninsula and up to southern Russian and Ukrainian peninsula of Crimea. In all of these areas, it tends to occur at higher elevations, usually >800 m a.s.l. (Meekers et al. 2012). In Kosovo it represents the most common species of the genus. It was recorded in different habitats ranging from 750 m up to 1550 m a.s.l. As we had records on silicate as well as calcareous substrates, it indicates that this species can successfully grow in either one of these substrate types. Due to the wide distribution of the species, we are convinced that especially G. conopsea must have an even wider distribution than we depict on the map (Fig. 1). From the available data, it was confirmed in the following EUNIS Habitat types in Kosovo: E2.1 Permanent mesotrophic pastures and aftermath-grazed meadows; E3.3 Sub-mediterranean humid meadows; E1.2 Perennial calcareous grassland and basic steppes; E1.7 Non-Mediterranean dry acid and neutral closed grassland; E1.73 Deschampsia flexuosa grasslands; E4.31 Alpic Nardus stricta swards and related communities; and E4.4 Calcareous alpine and subalpine grassland.

From this genus in Kosovo, undoubtedly one of the rarest and most fragile species is the Balkan endemic G. frivaldii. It is worth noting that this species previously has been assigned to the genus Pseudorchis Ség. (syn.: Leucorchis E.May) and just recently, molecular based analysis has confirmed that it belongs to the genus Gymnadenia (Bateman et al. 2003). Gymnadenia frivaldii is a species with a relatively small range in Europe limited to high-mountain belts on the Carpathians and the central and eastern Balkans (Delforge 2006). It has been reported for Albania, Kosovo, North Macedonia, Greece, Romania, Bulgaria, Montenegro, and Serbia (Diklić 1976; Bateman et al. 2006; Millaku ed. 2013, Djordjević et al. 2016, 2017; Berisha et al. 2020). This species prefers to grow on silicate substrates in fen communities and wet meadows of subalpine and alpine areas; occasionally it has also been recorded in pastures (of calcareous substrates too) as well as shrubs of the same altitudes in the mountains (Millaku ed. 2013). It has been reported (Djordjević et al. 2016) that this species is an indicator of an entire class (Scheuchzerio palustris-Caricetea fuscae Tx. 1937) of sedge-moss vegetation of fens in our region. The elevation distributional range was 1500–2600 m a.s.l. From the available data, mainly from the herbarium specimens, it was confirmed in the following EUNIS Habitat types in Kosovo: D2.2 Poor fens and soft-water spring mires; D2.22 Carex nigra, Carex canescens, Carex echinata fens; D2.26 Eriophorum angustifolium fens; D2.282 Balkan Willemetia fens; D2.3 Transition mires and quaking bogs and D2.38 Sphagnum and Eriophorum rafts.

Gymnadenia nigra was recorded on calcareous substrates of sub-alpine and alpine grasslands, or almost on all mountains exceeding 2000 m a.s.l. Based on the available data, it was confirmed in the following EUNIS Habitat types in Kosovo: E4.4 Calcareous alpine and subalpine grasslands; E1.7 Non-Mediterranean dry acid and neutral closed grassland and E1.72 Agrostis-Festuca grassland. All four relevés (Appendix 1) with this species, syntaxonomically fall into the Alliance: Seslerio juncifoliae-Caricion firmae Trinajstić 2005 (Alpine calcicolous sedge swards in wind-exposed habitats), though it has been reported also in different plant communities growing on limestone substrates (Rexhepi 1994). Also G. nigra previously has been assigned to Nigritella Rich. and Orchis Tourn. ex L., but phylogenetic studies (Bateman et al. 2003) have proved that it belongs to the genus Gymnadenia.

Gymnadenia odoratissima, a species very similar to G. conopsea, has an extensive distribution range in Europe. It is recorded from Spain in the west up to Ukraine in the east. Common in the mountain ranges of central Europe, up to the Sweden in the north and has been recorded also in Greece to the south. In Kosovo, Maja e Zezë massif represents the only known habitat of this species. It was recorded on silicate substrate, scattered in an area of ~1700 m², at an elevation ranging from 1680 m up to 1800 m a.s.l. Its corresponding habitat type was that of (EUNIS - E5.5721) Moesian Balkan thistle tall herb communities, and at the forest (rather degraded) margins of (EUNIS - G1.6933), namely the Balkan range subalpine beech forests.

Of the four relevés with G. conopsea (Relevés 1–4, Appendix 1), relevés 1, 3 and 4 belonged to the Alliance: Chrysopogono-Danthonion calycinae Kojić 1959, with the following species being dominant: Polygala major Jacq., Hypochaeris maculata L., Festuca nigrescens Lam., Danthonia alpina Vest. and Sanguisorba minor Scop. The richest relevé in terms of number of plant taxa was relevé no. 4., with 36 recorded plant taxa. Relevé no. 2 belonged to the Alliance: Trifolion resupinati Micevski 1957. It was recorded at a lower elevation (140 m) compared with the other ones of this group. The most dominant species in this relevé were: Hordeum secalinum Schreb. and Trifolium fragiferum L. As it is known, G. conopsea has a wider, more complex distributional range, though we aimed at offering its most common plant communities for comparative reasons. It was not our aim to define its syntaxonomical status, though this study can assist in that matter.

Of the four relevés with G. frivaldii (Relevés 5–8, Appendix 1), relevés 5, 6 and 8 belonged to the Alliance: Narthecion scardici Horvat ex Lakušić 1968. In these three calcareous relevés, the following plant taxa have been recorded as dominant ones: Narthecium scardicum Košanin, Pinguicula balcanica Casper, Gymnadenia frivaldii Hampe ex Griseb., Eriophorum angustifolium Honck. and Pinguicula leptoceras Rchb. Relevé no. 7 belonged to the Alliance: Cirsion appendiculati Horvat et al. (1937) based on its differential taxa. The most dominant plant taxa were: Cirsium appendiculatum Griseb., Eriophorum angustifolium Honck., Agrostis canina L. and Caltha palustris L. With a total of 31 recorded plant taxa, this was the relevé with the richest floristic diversity.

All four relevés with G. nigra (Relevés 9–12, Appendix 1) shared similar characteristics as they were all recorded on calcareous substrates. They all belonged to the alliance: Seslerio juncifoliae-Caricion firmae Trinajstić 2005, and the following taxa were recorded as dominant ones: Helianthemum nummularium (L.) Mill., Dryas octopetala L., Oxytropis jacquinii Bunge, Helianthemum canum (L.) Baumg., Bistorta vivipara (L.) Delarbre and Gymnadenia nigra (L.) Rchb.f. All relevés with G. nigra had high number of recorded plant taxa, with relevé no. 10 having 72 plant taxa recorded on one sampling site.

Of the three relevés with G. odoratissima (Relevés 13–15, Appendix 1), relevés 13 and 14 most likely should belong to the Alliance: Cirsion appendiculati Horvat et al. (1937), with the following taxa recorded as dominant ones: Barbarea balcana Pančić, Eriophorum latifolium Hoppe, Caltha palustris L., Cirsium appendiculatum Griseb., Cardamine pratensis L., and Helianthemum nummularium (L.) Mill. While the other remaining relevé on silicates (relevé no. 15) most likely should belong to the Alliance: Epilobion angustifolii Oberd. 1957. Epilobium angustifolium L. is the most dominant plant taxon in this relevé, as a characteristic species for the forest edges on silicate as well as a potential indicator of previously burned habitats or man-induced deforestation. High cover-abundance values on this relevé had also: Salix caprea L., Pimpinella saxifraga L. and Avenella flexuosa (L.) Drejer.

In the context of the vegetation diversity assessment, from only 15 relevés it was noticeable a very diverse vegetation affiliation by these four species of Gymnadenia. Four relevés belonged to Elyno-Seslerietea, three relevés to Festuco-Brometea, Scheuchzerio palustris-Caricetea fuscae and Mulgedio-Aconitetea respectively, and finally one releve belonged to Epilobietea angustifolii and Molinio-Arrhenatheretea respectively.

Commonly, all strategies for measuring biodiversity involve protecting a single species or several species of a given genus. Vegetation ecology contributes towards a better understanding of species indices of threats and a variety of interrelated paradigms in ecology (Cornell and Karlson 1996; Austin 1999). Furthermore, it also gives an incomparable insight into understanding the complex relationships between plant diversity, vegetation cover and site conditions (Wiesmair et al. 2017).

Although all of the four investigated Gymnadenia species are included in the European Red List of Vascular Plants (Bilz et al. 2011), all categorized as “LC” [Least Concern], more attention should be paid to those species that are more vulnerable and have fragmented habitats.

From this point of view, G. frivaldii is characterized by limited populations and a small number of mature individuals, with the exception of those in the Mts. of Gjeravica and Dobrosh. Nonetheless, since species populations are observed to be stable, its categorization as Near Threatened [NT] (Millaku ed. 2013) in Kosovo is completely reasonable.

Due to the large number of associated endemic species and their importance, we suggest that G. nigra populations in Kosovo also be assessed against conservation criteria and that monitoring measures be taken. In addition, the single population of G. odoratissima should be carefully monitored, as it represents the only habitat of the species in Kosovo.