ON THE PRESENCE OF CEPHALANTHERA CAUCASICA (ORCHIDACEAE) IN RUSSIA: REDISCOVERY OF A THREATENED ORCHID IN THE REPUBLIC OF DAGESTAN

Cephalanthera caucasica had been reported previously from the Samur Forest in Dagestan (Russia), but that report was considered doubtful: a possible misidentification of supposed hybrids between C. damasonium and C. longifolia as C. caucasica was speculated. Moreover, this species was recently reduced to a synonym of C. kotschyana in the «Plants of the World Online» database. In the present study, we did not confirm the presence of C. caucasica in the Samur Forest, but it was revealed in a few localities in remnants of beech ( Fagus orientalis ) forests in Kaytagskiy district and Tabasa� ranskiy district in the Republic of Dagestan, Russia. Living plants were studied in the vicinity of the village Tatil where 40 flowering individuals were counted. A morphological study suggested that these plants belonged to typical C. caucasica , not to any hybrid. The synonymy of this species with C. kotschyana has also been rejected, because it contradicted to the «International Code of Nomenclature for algae, fungi, and plants» and, besides, was not properly reasoned. The lectotype of C. caucasica is designated in the present paper. The description of the species is provided with measurements of the main morphological parameters. Differences of C. caucasica and the related taxa are discussed. A key to the species of the genus Cephalanthera from the North Caucasus is provided. Cephalanthera caucasica is highly threatened in Russia, being estimated as Endangered taxon (EN B1ab(iii)+2ab(iii)), according to the IUCN categories and criteria. It should be included to the next editions of both national and regional Red Data Books.


Introduction
The orchid family (Orchidaceae) is one of the most threatened groups of vascular plants (Fay, 2018;Khapugin, 2020;Wraith et al., 2020;Zhou et al., 2021).Approximately 28 000 spe� ).Approximately 28 000 spe� Approximately 28 000 spe� cies of orchids are known and it is the largest plant family in the world (Christenhusz & Byng, 2016).At least 135 orchid species were reported from Russia (Efimov, 2020).This is not particu� larly rich but the importance of their protection cannot be neglected.Russia is the largest coun� try in the world and some generally threatened species of orchids (e.g.Cypripedium calceolus L.) may be numerous within its territory (Jakub� ska�Busse et al., 2021).
The genus Cephalanthera Rich.(Orchidaceae: Epidendroideae: Neottieae) is distributed in the Holarctic and the Oriental regions and contains 19 species according to POWO (2022).Among them, Cephalanthera austiniae (A.Gray) A. Heller is known from North America, while all the other species inhabit the Old World.Seven species were listed for the Russian flora (Efimov, 2020).Cephalanthera damasonium (Mill.)Druce, C. longifolia (L.) R.M. Fritsch, and C. rubra (L.) Rich.are dis� tributed there in the European part, including the Crimea and the North Caucasus.Two other species are known from the Far East, namely Cephalanthera erecta (Thunb.)Blume and C. longibracteata Blume.The sixth species, Cephalanthera epipactoides Fisch.& C.A. Mey., is restricted in its dis� tribution to the Black Sea coastal area of the Kras� nodarsky Krai in the North Caucasus (Fateryga et al., 2020).All these species are included in the Red Data Book of the Russian Federation (2008).
The seventh species is Cephalanthera caucasica Kraenzl.It was reported from the River Samur delta in the Republic of Dagestan, North Caucasus (Grossheim, 1940;Averyanov, 2006;Murtazal� iev, 2009;Ivanov, 2019), but was included neither to the national Red Data Book nor the Red Data Book of the Republic of Dagestan (2020).Due to the absence of recent records of this species from the Republic of Dagestan, Efimov (2020) con� sidered C. caucasica doubtfully present in Rus� sia.He speculated that the reports of this species could be based on misidentifications of a possible hybrid between C. damasonium and C. longifolia, while the range of the true C. caucasica was out� side of Russia.It is also noteworthy mentioning that C. caucasica has recently been synonymised with C. kotschyana Renz & Taubenheim (POWO, 2022).The latter species was reported from Turkey and Azerbaijan (Delforge, 2016), while C. caucasica was known from Georgia, Armenia, Azerbai� jan (type locality in Talysh), and Iran (Renz, 1978;Akhalkatsi et al., 2003;Averyanov, 2006;Vakhra� meeva et al., 2008;Delforge, 2016).
The purpose of the present study is to ascer� tain, whether C. caucasica is present in Russia or not, to clarify its taxonomic status and diagnostic characters, as well as to report preliminary data on its distribution and conservation status.

Material and Methods
Field observations have been carried out in the Republic of Dagestan in 2022.Representatives of the genus Cephalanthera (excluding C. rubra) were studied there mainly in two localities, namely the vicinity of the village Tatil, Tabasaranskiy dis� trict (42.000278°N, 48.004722° E) on 04.05.2022, 08.05.2022, and 23.05.2022, and the Samur For� est in the vicinity of Khtun�Kazmalyar, Magara� mkent district (41.815556°N, 48.528611° E) on 07.05.2022.The first locality was a Fagus orientalis Lipsky (hereinafter -beech) forest, while the second one was a deciduous forest with the pre� domination of hornbeam (Carpinus betulus L.) and participation of oak (Quercus robur L.), ash (Fraxinus sp.), maple (Acer sp.), and other trees, and numerous creepers (e.g.Smilax excelsa L., Hedera pastuchovii Woronow, Vitis vinifera L.).Photographs of the studied plants were made with a Canon EOS RP digital camera and a Sigma AF 105 mm f/2.8 macro lens with a Yongnuo YN� 14EX macro flash and uploaded to the Plantarium website (Plantarium, 2022).
Twenty three plants were measured in the field with a metal tape measure.The measured param� eters were the shoot and the inflorescence lengths as well as the length and the width of the longest leaf.The number of leaves and flowers was also counted.After that, the lowest flower of the plant was cut and its straightened parts were placed be� tween a paper and a piece of a transparent adhe� sive tape.These flowers were then measured in the laboratory with a vernier calliper.The measured parameters were the length of the ovary, the length and the width of sepals and petals, the length of the lip, the width of the epichile, and the length of the column.Then, minimum, maximum, and mean values were calculated for each parameter.Confi� dence intervals of the mean values were calculated for 95% confidence level (p = 0.05).A morpholog� ical description was made according to the origi� nal data.Statistical significance of the differences between the mean values of various species was checked with the Student's t�test (Lakin, 1990).A PCA analysis was made using Statistica 7 software (StatSoft Inc., USA).
Literature data, herbarium material, and ob� servations on iNaturalist website (https://www.inaturalist.org/)were also studied.The data on herbarium specimens and their scans were pro� vided by Petr G. Efimov (V.L. Komarov Botani� cal Institute RAS, Russia) from his database of the orchids of Russia (for the complete list of the studied herbaria, see Efimov, 2020).A distribu� A distribu� tion map was generated, using the online tool for producing publication�quality point maps, Sim� pleMappr (Shorthouse, 2010).For specimens, for which no geographic co�ordinates were pres� ent on labels, co�ordinates were estimated based on the approximate centre of the most specific locality given.
For definition of the IUCN Red List status of C. caucasica at the national level (Russia), we used the guidelines for IUCN Red List assessment (2012a,b, 2022), focusing on the extent of occur� rence (EOO), the area of occupancy (AOO), and the number of the known localities.EOO and AOO were evaluated using GeoCAT, a geospatial con� servation assessment tool (Bachman et al., 2011).

Summary of records
We found 40 flowering specimens of C. caucasica and 20 specimens of C. damasonium in the vicinity of the village Tatil.They were counted along a 2�km transect (about 10 m wide) around the locality.There were also several pre� generative specimens of C. caucasica, but it was difficult to count all of them along this transect.Two additional herbarium specimens of C. caucasica collected in the Republic of Dagestan were found in collections of DAG and LENUD, and one observation was found on the iNatural� iNatural� ist website (https://www.inaturalist.org/).We did not reveal any specimens of this species in the Samur Forest, from where it had been reported in the literature (Grossheim, 1940;Ivanov, 2019).At this locality, the genus Cephalanthera were represented by one C. damasonium and more than 200 C. longifolia plants (counted along a 2�km transect, like in the vicinity of the village Tatil).Detailed information on C. caucasica is presented below, including its taxonomy, mor� phology, distribution, and conservation status.Kränzlin (1931) cited the gathering №2740 by R.F.Hohenacker in the protologue but did not indi� cate the number of specimens or herbarium sheets seen by him.Averyanov (1994) reported this gather� ing as the type of C. caucasica indicating that there are holo� and isotype(s) in LE.According to the Art.9.10 of ICN (Turland et al., 2018), this «holotype» would be corrected to «lectotype»; however, it is not clear, which specimen might be designated by L.V. Averyanov as the lectotype by this way.There are three sheets of C. caucasica (original material) in LE with Averyanov's handwritten labels from 1994.Two of them are with Hohenacker's №2740: LE01072106 and LE01072108.They are syntypes according to the Art.9.6 of ICN (Turland et al., 2018).Among them, only the first one is with F. Kränzlin's handwritten label (Fig. 1).Both sheets were labeled by L.V. Averyanov as isotypes.The third sheet (LE01072107) was labeled by him as «Typus»; this specimen is with the same F. Krän� zlin's handwritten label but without Hohenacker's №2740 that is not corresponding to the protologue.Therefore, it belongs to the original material ac� cording to the Art.9.4 of ICN (Turland et al., 2018) but not to the syntypes.Thus, since the L.V. Avery� anov's designation is unclear, a further lectotypifi� cation is possible according to the Art.9.17 of ICN (Turland et al., 2018).We hereby designate the specimen LE01072106 as the lectotype because it is with Hohenacker's №2740, fully corresponding to the protologue, and F. Kränzlin's handwritten la� bel indicating that he saw this specimen.
Cephalanthera caucasica has recently been synonymised with C. kotschyana (POWO, 2022).According to POWO (2022), the taxonomic back� bone for this solution was the book published by Kühn et al. (2019), where C. caucasica was merely listed as one of the synonyms of C. kotschyana without any argumentation.We do not follow such a taxonomic treatment of C. caucasica for two reasons.First of all, C. caucasica was described earlier (Kränzlin, 1931) than C. kotschyana (Renz & Taubenheim, 1980).Thus, the name C. caucasica published in 1931 has priority over the name C. kotschyana published in 1980.Accordingly, if these two taxa are treated as conspecific, the name C. caucasica should be accepted while the name C. kotschyana should be a synonym.Secondly, we prefer to recognise these taxa as two distinct species until they are thoroughly studied morpho� thoroughly studied morpho� thoroughly studied morpho� logically (and, possibly, genetically, too).There are at least two diagnostic characters declared to distinguish C. caucasica from C. kotschyana (see below).Thus, a statement of their synonymy with� out a strong argumentation looks not convincing.Therefore, we consider the genus Cephalanthera containing 20 species but not 19 as it was reported by POWO (2022).

Description
Cephalanthera caucasica is a rhizomatous perennial herb (Fig. 2A).Plants are usually with a single shoot.Stem is erect to slightly inclined, green, glabrous, with spirally arranged leaves.Leaves are green, spreading, significantly exceed� ing internodes; lower ones are ovate, medium ones are ovate to elliptic, upper ones are lanceo� late.Inflorescence is ± compact (Fig. 2B).Bracts are linear, usually not exceeding flowers, dimin� ishing in length higher up.Flowers are sessile, directed ± sidewards.Ovary is whitish, glabrous.Perianth is ± opened, pure white with light pink� ish shade on hypochile.Sepals are lanceolate; pet� als are broadly lanceolate, shorter than sepals.Lip is divided into hypochile and epichile.Hypochile is concave, with two erect, rounded lateral lobes, without spur.Epichile is cordate, with several or� ange�yellow longitudinal papillate ridges.Meas� urements are presented in Table 1.

Differences with the related taxa
Cephalanthera caucasica is sympatric with two relatively similar species, namely C. damasonium and C. longifolia.The characters of these three species are sometimes slightly overlapping (Fig. 3) which can cause misidentifications.The most noteworthy charac� ter of C. caucasica is the whitish ovary.It was stable in all plants from the Republic of Dagestan in our study, and this is in consistence with photographs published by Renz (1978) and Delforge (2016) from Iran and Azerbaijan, correspondingly.Only the drawing pub� lished by Vakhrameeva et al. (2008) has green ovaries that could be apparently due to its preparation based on a dried plant.Secondly, C. caucasica can be dis� tinguished from C. damasonium by much longer and more numerous leaves and from C. longifolia by much shorter (and not loose but compact) inflorescence and broader leaves.Flowers of C. caucasica are larger than those of both C. damasonium and especially C. longifolia (Table 1).In addition, the flowers of C. damasonium are directed rather upwards than sidewards.Cephalanthera caucasica is different from allopatric C. kotschyana by the whitish ovary and much lon� ger leaves.The latter species has a green ovary and leaves ± equal in length to the internodes, as in C. damasonium, but large flowers directed rather sidewards, as in C. caucasica (Delforge, 2016).Efimov (2020) supposed that the reports of C. caucasica from the Republic of Dagestan might refer to a hybrid between C. damasonium and C. longifolia.We cannot exclude the presence of such a hybrid in the Republic of Dagestan, but the plants identified as C. caucasica in the present study are not hybrids.First of all, both C. damasonium and C. longifolia have a green ovary, while C. caucasica has a whitish ovary.Secondly, the flowers of C. caucasica are not intermediate in size between two other species but are larger than those of both C. damasonium and C. longifolia.Thirdly, C. damasonium is an autogamous species (Claessens & Kleynen, 2011) and any hybrids with it should be extremely rare, while we observed 40 flowering specimens of C. caucasica within one locality.Fourthly, C. longifolia was not present in the locality with C. caucasica in our study.Therefore, we can state that C. caucasica is in� deed present in Russia.Moreover, it is not visually different from plants of this species occurring in Iran (Renz, 1978) and Azerbaijan (Delforge, 2016).

Distribution
Russia (Republic of Dagestan), Georgia, Ar� menia, Azerbaijan, Iran (Renz, 1978;Akhalkatsi et al., 2003;Averyanov, 2006;Vakhrameeva et al., 2008;Delforge, 2016).The records from Geor� gia and Armenia are based on literature data (e.g.Vakhrameeva et al., 2008) and require further veri� fication (especially for Armenia).In the Republic of Dagestan, C. caucasica is distributed locally.There are four known localities in Kaytagskiy dis� trict and Tabasaranskiy district (Fig. 4), or even three, since the records made by A.A. Teymurov and by us were made nearly at the same place.The presence of C. caucasica in the Samur Forest, from where it was reported in the literature (Grossheim, 1940;Ivanov, 2019), is also doubtful and requires confirmation.We observed there nu� merous plants of C. longifolia, and some of them had unusually broad leaves (Fig. 5).Such plants could be misidentified as C. caucasica.How� ever, we failed to find the voucher material used by Grossheim (1940) who was apparently the first person reported C. caucasica from the Samur For� est.Due to the absence of any specimen�based re� cords we did not include this locality to the distri� bution map (Fig. 4).

Habitat, phenology, and pollination
We observed C. caucasica in a beech forest only.The flowering period of this species is May.It starts to flower at the same time as C. longifolia (evidences from herbarium gathering of both spe� cies from the vicinity of the village of Gurkhun) but much earlier than C. damasonium.Apparently, there are no published data on pollinators of C. caucasica.We can suppose that the pollinators are solitary bees, and the pollination strategy is a food�deceptive mechanism, which is known in C. longifolia (Dafni & Ivri, 1981;Claessens & Kleynen, 2011).

Conservation status
We consider C. caucasica a highly threatened species.It occurs in Russia at a few localities within a small area of Kaytagskiy district and Tabasarans� kiy district of the Republic of Dagestan.These lo� calities are remnants of beech forests between settle� ments, orchards, and meadows used for haymaking.The forest remnants themselves can be used as a pasture for cows, since we observed such a case in the vicinity of the village of Tatil.The population number of C. caucasica is evidently very low in Russia.Cephalanthera caucasica is one of the two rarest species of the genus in Russia (the second one is C. erecta), and at the same time it is the only spe� cies of Cephalanthera which is not included in the Red Data Book of the Russian Federation (2008).
In Russia, the estimated IUCN Red List category for C. caucasica is EN B1ab(iii)+2ab(iii).Its EOO is evaluated to be 32.5 km 2 , which is less than 5000 km 2 , and the number of the known localities is no more than five (actually no more than four), that fits to the criterion B1a of the EN category.At the same time, threats have been identified that indicate a con� tinuing decline in habitat quality (due to its use as a pasture), that fits to the criterion B1b(iii).The AOO is evaluated to be 16.0 km 2 , that is less than 500 km 2 , so that both criteria B2a and B2b(iii) are also met.

Conclusions
Cephalanthera caucasica is present in Kaytags� kiy district and Tabasaranskiy district of the Republic of Dagestan (Russia) without any doubts, although in a few localities and by a low number of individu� als.The presence of this species in the Samur Forest, reported earlier in the literature (Grossheim, 1940;Ivanov, 2019), could not be confirmed.Cephalanthera caucasica is a distinct species, but not a syn� onym of C. kotschyana and not a hybrid between C. damasonium and C. longifolia either.This species should be included in the next editions of both na� tional and regional Red Data Books.