СТАТЬИ REMNANT POPULATIONS OF CYPRIPEDIUM MACRANTHOS (ORCHIDACEAE) IN EASTERN EUROPE: EVIDENCE OF ALMOST COMPLETE EXTINCTION AND WIDESPREAD INTROGRESSION WITH CYPRIPEDIUM CALCEOLUS

The distribution of Cypripedium macranthos and C. × ventricosum in Eastern Europe is described in the literature controversially. At the same time, Cypripedium species are legally protected plants of the highest conservational importance, and detailed knowledge about their historic and current distribution is essential for correct setting of conservation priorities. In the present article, we have assembled primary information about localities of C. macranthos and C. × ventricosum in Russia and Ukraine by referring to the original information sources, mostly to old herbaria and literature. As a result, 19 localities have been estimated as incorrect, 11 as doubtful and only 12 as reliable. Historical absence of C. macranthos and C. × ventricosum in the Republic of Chechnya, Republic of Mari El, Ulyanovsk Region and Kursk Region has been confirmed, whereas its presence in the Republic of Udmurtia, Nizhniy Novgorod Region, Vologda Region, Yaroslavl Region, Republic of Komi, and Voronezh/Lipetsk Regions is questioned. Original herbarium specimens con-firming its locality in the Samara Region have been found in the herbarium. The existence of the species in Ukraine is being discussed in view of the information published by V.G. Sobko in 1989, but omitted in later publications. A sharp decrease in the number of localities has been proven. The only extant locality of C. ma cranthos is situated in the Republic of Chuvashia, and that of C. × ventricosum (1–4 subpopulations) in the Bryansk Region. The amount of hybridisation between C. macranthos and C. calceolus in Eastern Europe was previously underestimated. In the part of the species’ distribution centered in Bryansk Region, only hybrids have been recorded since 1903. This fact determines the need for corresponding changes in floristic data and in documents which establish local plant protection.


Introduction
Cypripedium macranthos Sw., along with its more common congeners C. calceolus L. and C. guttatum Sw., are remarkable and belonging to the most widely known orchid species in North-Temperate Eurasia. Their peculiar brightly-coloured flowers and diversity of hybrid cultivars attract both plant hunters and gardeners. The involvement of these plants into illegal trade is considered as one of the causes for their rarity or even complete extirpation in many localities in the current time (Averyanov, 1999(Averyanov, , 2000Rännbäck, 2007;Jakubska-Busse et al., 2021). All species of the genus Cypripedium are included into the Red Data Book of the Russian Federation (Bardunov & Novikov, 2008) and are legally protected in all Russian regions where they occur.
The natural ranges of C. macranthos and C. guttatum are spread mainly in Asia, within Russia covering vast territories in Siberia and the Far East. But they also extend westwards from the Urals to Europe, where both species are becoming substantially rarer than in Asia (Averyanov, 1999(Averyanov, , 2000Vakhrameeva et al., 2014). Cypripedium macranthos is known for its ability to produce hybrids with the more widespread C. calceolus, which were described taxonomically under the name of C. × ventricosum Sw. (Averyanov, 1999(Averyanov, , 2000Knyasev et al., 2000a,b). This hybrid was similarly reported from a few localities in European Russia, but not so frequently as C. macranthos.
In Europe, many localities of C. macranthos are historical, due to the shrinkage of its natural range (Averyanov, 1999(Averyanov, , 2000. Accordingly, many of them are based on old and imprecise literature reports and/or old herbarium specimens without indication of detailed localities. Therefore, the information about the distribution of Cypripedium macranthos and C. × ventricosum is full of various sorts of confusion, incorrect determinations and even fraud. The situation has been further entangled by changes in the administrative division of the USSR, which took place in the first half of the XX century. It proves to be problematic or even impossible to apply some of the old records to the present-day Russian regions. As a result, there are misleading interpretations for some Russian regions, including Kursk Region, Ulyanovsk Region, Starodub District and Brasovo District of the Bryansk Region and possibly for some other localities as well. The overall situation is similar to that with another rare orchid of Russia, Gymnadenia odoratissima (L.) Rich, which was also reported from many localities according to old incorrect data (Kulikov & Filippov, 2011). Another additional factor is that the reports of C. macranthos, widely known as an ornamental plant, both now and in the past, may belong to cultivated individuals, not being properly indicated as such.
As a result, without addressing to the original sources of information, floristical treatments tend to accumulate incorrect information. The examples are essays about C. macranthos in the second edition of the Red Data Book of the Republic of Tatarstan (Shchepovskikh, 2006), and the first edition of the Red Data Book of the Republic of Chuvashia (Dimitriev, 2001). Republic of Chuvashia is an example where recent sources are gradually replacing the previously unconfirmed data (Gafurova, 2014(Gafurova, , 2019. The distributional data about Cypripedium species in various editions of the Mayevskiy's flora (1917,1933,1941,1954,1964,2006,2014) are strongly different from each other. In the detailed review of the Cypripedium of Russia associated with its mapping, Averyanov (1999Averyanov ( , 2000 treated all localities of C. macranthos and C. × ventricosum to the west from the River Volga as doubtful. In contrast, Vakhrameeva et al. (2014) assumed that at least C. macranthos is present as a native element in the Bryansk Region, Belgorod Region, and Orel Region.

Material and Methods
In the course of the present study, we have assembled the original data about C. macranthos and C. × ventricosum in Eastern Europe from literature sources and herbarium collections, and where possible, supplemented them with the unpublished data after direct observations in the field. The field studies were undertaken in the Bryansk Region in 2021 focusing on the taxonomy of plants, which still occur there under natural conditions.
The study is largely based on the data from the database «Orchids of Russia», in prospect aimed to prepare detailed maps of all orchid species known in Russia (Efimov, 2020). The currently assembled information includes complete or almost complete data from 82 herbarium collections of Russia (Appendix), including the 25 largest ones in Russia (excluding RV and MOSM). In this article, we give full citations of all herbarium specimens of Cypripedium macranthos and C. × ventricosum from Eastern Europe we managed to discover.
In the current study, in the west, «European Russia» is limited by administrative regions which do not include the Ural Mountain Range, except for the Republic of Komi. Administrative Regions of Russia are understood here as the 1 st -level administrative units of the country. The federal cities (Saint-Petersburg and Moscow) are included into their largest nearest regions, namely Leningrad Region and Moscow Region, respectively. In relation to the herbarium specimens, abbreviation «C.m.» was used for Cypripedium macranthos, and «C.v.» for C. × ventricosum in the review of their localities.
Vologda Region. In the Vologda Region, C. macranthos was reported only in 1972 in the Protected Area «Severnye Orkhidei», in the vicinity of the village of Boyarskaya, Vozhegodskiy District (Konechnaya & Suslova, 2004). Vakhrameeva et al. (2014) claimed that this record is based on a herbarium specimen. Possibly, the record is based on an incorrect determination, because the later biodiversity description of the Protected Area «Severnye Orkhidei» (Sobolev & Belonovskaya, 2013) does not mention this taxon among other orchids. The re-determined vouchers for this record may be kept in the herbarium of the Vologda State University. Unfortunately, the curator of this collection (Andrey Chkhobadze) was unable to provide us with an access to examine the herbarium in 2020-2021.
Republic of Komi. There are several reports from the Republic of Komi.
Troitsko-Pechorsk District. In addition to the locality along River Bol'shaya Synya, Yudin (1963) reported C. macranthos from the limestone outcrops along the River Ilych, which was subsequently repeated by Martynenko (1976). This is possibly a misprint because, judging by the other place of the same report (in page 531), it is clear that the locality along the River Bol'shaya Synya was the single locality of C. macranthos known to this author in the Republic of Komi.
Ust'-Tzil'ma District. Bolotova et al. (1962) guided by some unspecified information source also reported C. macranthos from the River Tzil'ma basin. This was subsequently repeated by Martynenko (1976), but reasonably questioned by Averyanov (1999Averyanov ( , 2000. Yaroslavl Region. «Pereslavl' District, Nagor'evskoye bog, «islands», 09.07.1980, Senatskaya» (USPIY!, C.m.). The plant is rather typical in appearance, but there is no determination on its label. The species was never reported from the Yaroslavl Region in the literature (e.g. Tikhomirov, 1986;Marakaev, 2015;Nyankovskiy, 2015). Here, this locality is formally treated as doubtful, but it can also mark a true isolated locality in the peripheral part of the species range.
Republic of Udmurtia. The only source is a herbarium specimen with the incomplete label, originally bearing only the name of the species: «sandy places in coniferous forests, possibly Sarap. [ul]?» (UDU!, C.m.). This locality was referred to the 1960s in the Red Data Book of the Republic of Udmurtia (Baranova, 2012), and it is repeated several times in the literature (Efimova, 1972;Baranova & Puzyrev, 2012), but absent in Baranova et al. (1992). The information about this locality in Udmurtia that it was still extant in the 2000s (Vakhrameeva et al., 2014), is an incorrect interpretation of the data by Baranova (2000). Subsequently published sources did not confirm this information either (Baranova, 2006;Baranova et al., 2011;Baranova & Puzyrev, 2012;Nazirov, 2016). Due to the absence of the original label and questionable interpretation of the locality, the corresponding locality is treated as unconfirmed.
Republic of Tatarstan. There are several reports from the Republic of Tatarstan.
Vysokogorskiy District. A locality near the Semiozernaya Pustyn' monastery on the slope near the village of Semiozerka is widely known, being visited by several generations of botanists (Wirzen, 1839;Claus, 1851;Ruprecht, 1866;Kryshtofovich, 1929), but there is only one herbarium specimen with a plain label. It has been only recently incorporated into the main herbarium collection, and it included both hybrid and non-hybrid individuals («grows in the forest of Semiozernaya Pustyn' in Kazan, 23.05.1818» (LE 01107814!, C.v.;LE 01107815!, C.m.). A herbarium specimen «Kazan Gub., 1894» (MW 295230!, C.m.) also most likely originates from this locality, the same as four specimens in the herbarium of P.Ya. Kornukh-Trotzky dating back to the 1830s: «Gub. Kazan, Korn.-Tr., N 541 [2 sheets], N 542 [2 sheets]» (KAZ!, C.m.). The last record from this locality is ascribed to Korzhinsky (Shchepovskikh, 2006), but no data which confirm this, are traced in Korzhinsky's publications, which means that it might already have gone extinct by that time.
The former Menzelinsk County. «Gub. Ufa, distr. Menselinsk, in the forests, 1871, Lossiewski, N 353» (LE 01107811! and LE 01107812!, both C.v.). The exact locality is unknown, and theoretically, it may be referable to the presentday territory of the Republic of Bashkiria. The information in Smirnov (1979) and subsequently in three editions of the Red Data Book of the Republic of Tatarstan (Shchepovskikh, 1995(Shchepovskikh, , 2006Nazirov, 2016) is different and possibly incorrect: here the locality is associated with the Krasnoborskoye Forestry of the present-day Menzelinsk District, dated on 1934.
Elabuga District. A report from «Bol'shoye Pole» of the Elabuga District has appeared only in the 2 nd edition of the Red Data Book of the Republic of Tatarstan (Shchepovskikh, 2006) as if it was originally published by Krylov (1885), but no original information can be traced in this publication.
Republic of Chuvashia. There are several reports from the Republic of Chuvashia.
Poretskiy District. It was reported by Dimitriev (2001) and Gafurova (2014Gafurova ( , 2019 after it was incorrectly determined C. calceolus specimen «Ulyanovsk Gub., Alatyr' County, Siyava village, in a boggy spruce forest at the bottom of the slope of the river valley, 30.07.1916, A.P. Shennikov, N 355» (Herbarium of the Ulyanovsk Natural History Museum!). Its duplicate and some other A.P. Shennikov collections kept in the herbarium LE were also originally determined incorrectly in the same way.
Cheboksarskiy District. A locality near Cheboksary was based on the personal communication of L.P. Teplova (Dimitriev, 2001;Gafurova, 2014). This locality was excluded from the new edition of the Red Data Book of the Republic of Chuvashia (Gafurova, 2019), as a dubious record, because L.P. Teplova did not remember the case (Margarita M. Gafurova, pers. comm).
Alatyr' District. This locality is reported by Dimitriev (2001). It is possibly a mistake based on the aforementioned collection from the village of Siyava, belonged to the former Alatyr' County according to the old administrative division. This record is omitted in the later reviews of Chuvashian flora (e.g. Gafurova, 2014Gafurova, , 2019.
[County], the only locality: the chalk slope with a pine forest near «Rustovskiye Klyuchi», 1903, Yanishevskiy, N 149» (KAZ!, C.m.). These typical C. macranthos herbarium specimens were possibly not consulted for years, and the species was cited according to the literature data, originally by Smirnov (1904), which caused some confusion in the subsequently published literature. Although Smirnov (1904) correctly reported C. macranthos for this locality, many later published literature sources reported hybrids C. × ventricosum instead (e.g. Mayevskiy, 1917Mayevskiy, , 1933Mayevskiy, , 1941Mayevskiy, , 1954Mayevskiy, , 1964Mayevskiy, , 2006Plaksina, 2001;Saksonov & Koneva, 2006) or both C. macranthos and C. × ventricosum (Saksonov & Senator, 2012;Mayevskiy, 2014). This may be incorrect, as far as all herbarium specimens are attributable only to the species C. macranthos. Some confusion has also been created by the problematic attribution of the locality to the exact geographic place. Litvinov (1927) roughly attributed it to the vicinity of the town of Sengiley, which was probably the reason why, in Mayevskiy (1954), the locality was incorrectly understood as belonging to the Ulyanovsk Region, which was later repeated by Rakov et al. (2014) as well. In contrast, in Mayevskiy (2014), the locality was moved to another direction, namely the Zhiguli Mountains. In fact, Rustovskiye Klyuchi village, later renamed to Smyslovo (Mayevskiy, 1917(Mayevskiy, , 1933(Mayevskiy, , 1941, was situated between the villages of Novodevichye and Klimovka, belonging to the present-day Shigony District of the Samara Region (Stepan A. Senator, pers. comm.). The village is absent on the public maps, probably due to a very short time of its existence, being flooded in the 1950s by the Kuybyshevskoe Reservoir. However, in this locality, plants may have perished long before the building of the Kuybyshevskoe Reservoir because, almost 100 years ago, Litvinov (1927), while discussing the depletion of his «mountainous» type of the pine forest in the steppe zone, stated «by rumour» that the forest in the Cypripedium's locality had already been «cut down by the time of this publication. It should also be taken into account that there may have been not one but two localities: one herbarium label bears the name of «Beloklyuchye», which is a village different from the village Rustovskiye Klyuchi. Certain doubts about the correctness of the collection in Beloklyuchye may be traced from Smirnov (1904), who referred C. macranthos only from Rustovskiye Klyuchi, and from the text of Yanishevsky's herbarium label.
Ulyanovsk Region. All reports of both C. × ventricosum and C. macranthos from the Ulyanovsk Region are in fact based on the incorrect interpretation of the C. macranthos locality in the Samara Region (see above).
Penza Region. The record of C. × ventricosum in the Bessonovka District in July 2018 (Ueda, 2021b) obviously belongs to a cultivated individual judging by an image, although not labelled as such.
Republic of Mari El. As far as we are aware, the report for the Republic of Mari El appears only in the description of the overall species distribution in the Red Data Book of the Republic of Tatarstan (Nazirov, 2016). This is possibly a mistake.
Orel Region. There are several reports from the Orel Region.
Shablykino District, near Molodovoye: «Orel Gub., Karachevsk. County, Molodovoye, Teplov, N 1321» (MW 295227!, C.m.); «Flora of the Orel Region, forest near Molodovoye, 01.06.1909, V. Khitrovo» (OHHI!). The hybrid origin of the latter specimen cannot be checked, because the flower is lost. The report from the western part of the Karachev County by Zinger (1886) «in sandy places in coniferous forests» is most likely based on the same record.
Uritskiy District. It was reported from «Chernevye forests of the Naryshkino District» in Ammosov et al. (1978). «Chernevye lesa» stand for broad-leaved forests, and their interpretation, as the local name «Chernevskiye lesa» (Bondartseva & Prisnyi, 2021), is incorrect. This locality falls into the present-day Uritskiy District (Kiseleva et al., 2021). It should be taken into account that the time period, when this record was made, is unknown. Moreover, the information about this locality cannot be verified, as it seems to be based on personal memoirs, which may be incorrect.
Belgorod Region. It was reported by Maltsev (1907) for the former Korocha County: «7/ VI 1905, solitary specimens in the state forest near the village Likhaya Polyana, on the road to Zimovnoye; very rare». This locality belongs to the present-day Shebekino District, the village of «Likhaya Polyana» renamed to «Krasnaya Polyana». In the subsequently published sources, the taxon was reported for the Belgorod Region without detailed localities by Mayevskiy (1933Mayevskiy ( , 1964Mayevskiy ( , 2006Mayevskiy ( , 2014, and in the Red Data Book of the Belgorod Region (Prisnyi, 2005), as an extinct taxon.
Kursk Region. Cypripedium macranthos was reported by Mayevskiy (1941Mayevskiy ( , 1954 from the Kursk Region based on the incorrect georeference of the previously discussed locality in the former Korocha County, which was previously located within the former Kursk Province («Kurskaya Gouberniya»). But now it belongs to the Belgorod Region.
Voronezh / Lipetsk Regions. There are two specimens in the Herbarium of Voronezh State University (VOR 24316!; VOR 24338!) without original labels, inscribed as collected «possibly in Voronezh or Lipetsk Regions». Both represent large C. macranthos specimens in fruits and seem to have been collected not long ago, possibly in the last 10-40 years, and they may originate from cultivation or from some distant Asiatic parts of Russia.
Bryansk Region. There are several reports from the Bryansk Region.
Karachev District. It was reported by Bosek (1975) without detailed locality and by Bosek (1982) for the vicinity of the town of Karachev. We consider those data as not reliable, because the original source of this information is unclear. They may be based on the incorrect interpretation of the localities from the former Karachev County, which in fact belong to the present-day Orel Region (see above).
Surazh District. From Surazh District, only doubtful information exists. It was reported in the Red Data Books of the Bryansk Region from the village Kostenichi (Fedotov, 2004;Bulokhov et al., 2016) as if it had previously been reported by Bosek (1975Bosek ( , 1982, which in fact is not the case. Thus, the original source of this information is unclear.
Navlya District. All recent and presently known localities belong here. But only hybrids C. × ventricosum have been confirmed. In the last 20 years, four localities were recorded, all belonging to a rather limited area in the Gavanskoye (formerly Saltanovskoye) Forestry at several kilometres from the village Prolysovo: in the forestry quarter 28 and quarter 29 in and 2002(Fedotov & Evstigneev, 2003, and two localities in forestry quarter 39 in 2007 and 2010 (Bulokhov et al., 2016), the latter being extant in 2021 (authors' unpublished data). The older reports from this area («near Prolysovo») (Khitrovo, 1910) and «2 km south from Prolysovo» (Tikhomirov & Kharitontsev, 1984) cannot be confidentially attributed to any of the above-mentioned localities and may also represent different localities, which are now lost. Five herbarium specimens are known from the Navlya District: «near the village of Prolysovo, a mixed forest, 2000» (BRSU VP3021!, C.v.); «25 from BAM, a pine woodland, 05.06.2001, 05.06.2001, 12.06.2001, N 344» (Herbarium of the Bryansk Forest State Nature Reserve!, C.v., three specimens); «2 km south from the village Prolysovo, wet spruce forest, 30.05.1978, B.S. Kharitontsev» (MW 295228!, C.v.). It should be noted that the collector of the latter specimen, Boris Kharitontsev, is a person who is known in the Russian botanical society for his recently published contributions characterised by «zero or even negative scientific value» (Geltman & Matveeva, 2018), leaving doubts about his other research as well. However, there is no criticism of his previous floristic studies at the time of his PhD Thesis based on the material from the Bryansk Region.
Komarichi District. «Orel Province, Sevskiy County, 285 forest quarter of the Komaritskoye Forestry of the Grand Duke Mikhail Aleksandrovich» (Khitrovo, 1910). The exact location of this place is unknown. It might be the same place as the previously mentioned one in the Sevskiy District. It may also belong to the bordering parts of the Brasovo District.
Brasovo District. It was reported by Bulokhov & Velichkin (1998), possibly after the locality in the former Komaritskoye Forestry. In fact, it most likely belongs to the Komarichi District (see above).

Cypripedium macranthos and C. × ventricosum localities in Ukraine and Belarus
Cypripedium macranthos was reported from the present-day territory of Ukraine in several literature sources (Smolyaninova, 1976;Borodin, 1984) but without detailed localities. Probably, the primary sources were publications by Kleopov (1933) and Bordzilovski (1950). In these sources, an assumption about further possible finding of this species in the Chernigov Region of Ukraine was expressed, taking into account the neighbouring localities in the Bryansk Region of Russia. The historical localities in the former Chernigov Province near the villages Krasnyi Rog and Rogovichi may also have been taken into account by Kleopov (1933) and Bordzilovski (1950). However, both villages ac-cording to the modern administrative division belong to the Bryansk Region of Russia, unlike the major part of the former Chernigov Province which is in present-day Ukraine.
There are also two herbarium specimens (probably 150-200 years old), which might previously have been interpreted as collected in the Ukraine, which can hardly be the case. One is «Rossia minor, herb. Fleischer, N 3044.7» (LE 01107813!, C.v.). Here, the toponym «Rossia minor» («Little Russia») may refer not only to Ukraine, but also to the bordering parts of the Bryansk Region and some other Russian regions. Another doubtful specimen «in montosis ad Catherinopolin haud vulgaris» (LE 01107810!, C.m.) was unlikely collected near the town of Catherinopol (now it is a village in the Cherkassy Region of Ukraine) because it is ca. 500 km south-south-west from the nearest confirmed localities. Most possibly, it was collected near the city of Yekaterinburg (Ural Mountains), where C. macranthos may be rather common, as it is given on the label. The mistake may be derived from the similarity of the toponymical names.
Later, Protopopova (1987) did not provide any reports of this taxon from Ukraine. The most recent checklist of the Ukrainian flora (Mosyakin & Fedoronchuk, 1999) claims that the records of this species need confirmation. Averyanov (1999Averyanov ( , 2000 mentions two herbarium specimens from Ukraine that probably originated from cultivated or introduced plants. But both, collected near Krasnyi Rog village and Rogovichi village, in fact belong to the present-days territory of surroundings of the Bryansk Region, Russia. However, none of the contributors cited above were aware of the fact that this species was indeed reported from Ukraine ca. 100 km west from the border with Russia by Sobko (1989): «in Ukraine, the only locality is known near the village Kachanovka, Ichnya District, Chernigov Region, in an oak forest». Sobko (1989) additionally left us a short description of the vegetation cover in this locality, and the information that the population included 27 young plants, but no generative individuals, possibly because flowering individuals were transplanted by local people. One plant flowered subsequently in culture. Also Sobko (1989) stated that the plants might have originated from culture, as the author had information that C. macranthos was indeed cultivated in one arboretum not far from the lo-cality. In the later accounts of Ukrainian flora, this information has never been repeated again, including the pinpointed review of Cypripedium of Ukraine (Reshetiuk, 2003), led by V.G. Sobko. This fact is explained by V.G. Sobko's colleagues in the way that he had got convinced about the origin of these plants from cultivation (Irina Timchenko, Sergey Mosyakin, pers. comm.).
The interpretation of this locality is very controversial indeed. The assumption of Sobko (1989) that the species is a residue of cultivation seems doubtful, because this species has never been reported as such. According to our personal experience, as soon as the plants are abandoned, they disappear rather quickly without proper management. Several other alternatives seem to be possible. One is that the plants may have been mixed up in the field with C. calceolus, because no generative individuals have been observed, which is important for correct determination. Later, during cultivation, plants may have been mixed up with C. macranthos individuals originating in culture from a different source. In addition, any other type of mistake may have occurred, making Sobko'data (1989) to be incorrect. Last but not least, it cannot be discarded that in surrounding Russia, at a distance of ca. 180 km, there is an area with C. macranthos / C. × ventricosum localities. Therefore, plants observed by V.G. Sobko may also be native, thus representing part of their continuous natural distribution. However, the latter assumption is the least realistic, because the area around the village Kachanovka is very densely populated, and no primary type of forest vegetation can be present there, whereas, in adjacent Russia, all localities are always connected with problematically accessible localities and native forest remnants.
Cypripedium × ventricosum was reported in the literature for Ukraine as a possible finding in view of the existing locality in the former Starodubsk County, which is referable to the present-day Bryansk Region of Russia (Kleopov, 1933;Bordzilovski, 1950). Then, it was reported by Smolyaninova (1976) for Ukraine in general, but later it was reasonably questioned again by Mosyakin & Fedoronchuk (1999) and Averyanov (1999Averyanov ( , 2000. In fact, the only possible, but very unlikely, finding of this hybrid in Ukraine is the specimen mentioned above (LE 01107813!) and data previously discussed by Sobko (1989).
In Belarus, neither C. macranthos, nor C. × ventricosum were ever reported in any re-gional literature. The indication of C. macranthos by Averyanov (1999Averyanov ( , 2000 in Belarus is definitely a mistake.

Geography of the western portion of distribution range of Cypripedium macranthos and C. × ventricosum
Summarising all existing literature and herbarium sources, in European Russia, 38 localities of C. macranthos and C. × ventricosum in 16 of 44 regions have been reported so far (Table). Several localities concentrating near the village Prolysovo are formally treated in the Table as one. Of these 38 localities, 16 are treated as incorrect for various reasons, and in five regions (Republic of Chechnya, Republic of Mari El, Ulyanovsk Region, Penza Region, Kursk Region) only incorrect reports exist, which means that C. macranthos and (or) C. × ventricosum should not be included in corresponding local flora's accounts. Ten localities are treated as doubtful for various reasons, providing only doubtful information for six regions (Vologda Region, Yaroslavl Region, Republic of Komi, Republic of Udmurtia, Nizhniy Novgorod Region, Voronezh / Lipetsk Regions). Twelve localities are treated as fully reliable; ten of them are confirmed by herbarium specimens.
The geographic position of C. macranthos and C. × ventricosum localities in Eastern Europe is shown in Fig. 1. All localities may be classified in four groups according to geographic principle, as follows: 1) The localities in the River Volga basin, adjacent to the main distribution range of C. macranthos in the Ural Mountains, representing part of continuous species distribution. It is the only group, which was recognised as doubtless by Averyanov (1999Averyanov ( , 2000.
2) The localities in the west of European Russia and in Ukraine, centered in the Bryansk Region of Russia, with a solitary unconfirmed locality in adjacent Ukraine. This portion of species' range is currently isolated from the main distribution range by a gap of ca. 800 km and makes an impression of a relict part of the distribution, a feature already noted by Khitrovo (1910). In this area, only localities in the Navlya District of the Bryansk Region seem to be still extant. In the last 100 years, only C. × ventricosum was recorded in this part of the species range. The supposition by Averyanov (1999Averyanov ( , 2000, that this portion of distribution had been reported by mistake, proved to be incorrect. 3) Five scattered localities in the north of European Russia (three localities in the Republic of Komi, one in the Vologda Region, and one in the Yaroslavl Region), representing either evident mistakes, or unconfirmed data. This is a doubtful part of the species distribution.
4) The locality in the Caucasus, which is a certain mistake. This has been discussed with full details in the list of localities above.

Habitats of Cypripedium macranthos and C. × ventricosum in Eastern Europe
In the basin of the River Volga, C. macranthos occurs almost exclusively at the chalk or limestone outcrops on the slopes, covered with pine forests. These slopes are typically associated with the River Volga valley and its major tributaries of the River Kama and the River Sura, more rarely with smaller rivers such as at the locality near the city of Kazan. Such habitats represent a rare and rather specific type of plant communities, interpreted by Litvinov (1927) as the «mountain type» of pine forests, which occurs in the plain in scattered localities along the river valleys. The depletion of this forest type leads to the subsequent extinction of C. macranthos.
River valleys may not only provide specific habitat type, but may also indicate the main dispersal route of C. macranthos. The River Kama, as well as many other major left-bank tributaries of the River Volga, have their source in the Ural Mountains, where C. macranthos persists up to the present days in many localities (Knyasev et al., 2000a,b).
The isolated group of localities, centered in the Bryansk Region, is associated with pine forests, or oak forests, as well as with the variety of intermediate forest types. Khitrovo (1910), who was probably better informed than anyone else about C. macranthos in this area, characterised the habitats as follows: «places intermediate between those dominated by Pinus, and Quercus, i.e. where the soil is already sandy but not yet typical for Pinus forests». It is still unclear whether the habitat variety correlates with taxonomy, i.e. with specific requirements of hybrid and non-hybrid plants. No association with major rivers can be traced in this area. It is also typical that the plants were usually found in the least accessible localities in the forest remnants, thus giving an impression that the plants are connected with the primary vegetation. The localities, which presently persist, are situated in an extension of the widely known forest massifs called «Nerusso-Desnyanskoye Polesye», with its weakly disturbed forests protected in the Bryansk Forest State Nature Reserve. A large gap in the distribution of C. macranthos in European Russia may be connected with the rareness of appropriate habitats.

Evidence of wide introgressive hybridisation between C. calceolus and C. macranthos in Eastern Europe
There is a self-evident problem of distinguishing between C. macranthos and C. × ventricosum when the information about localities is not confirmed by herbarium specimens, which is the case for some records in Eastern Europe. Moreover, herbarium specimens may be not enough for final conclusions either when only a part of existing taxonomic diversity has been collected. The general distribution of C. × ventricosum is tightly associated with the area where both parental species co-occur, but it is more common in the Ural Mountains and Primorsky Krai of Russia (Knyasev et al., 2000a,b).
In localities within the River Volga basin, the existing data show the predominance of C. macranthos, similar to the main Asiatic portion of the species distribution. Of five localities, which can be checked taxonomically by herbarium specimens, there are hybrids in only one locality (Menzelinsk County), non-hybrid plants in three localities (Urakovo, Rustovskiye Klyuchi, Sarapul), while both hybrid and non-hybrid plants have been recorded only in one locality (Semiozernaya Pustyn'). Previously, hybrids were noted in the literature either provisionally (Bakin et al., 2000) or without a reference to any particular localities (Averyanov, 1999(Averyanov, , 2000Mayevskiy, 2006Mayevskiy, , 2014. In the Ulyanovsk Region, information about hybrids (Mayevskiy, 1917(Mayevskiy, , 1933(Mayevskiy, , 1941(Mayevskiy, , 1954(Mayevskiy, , 1964(Mayevskiy, , 2006(Mayevskiy, , 2014Rakov et al., 2014) is incorrect, being based on misinterpretation of the finding in the Samara Region, near the former village Rustovskiye Klyuchi, where, in fact, no hybrids were recorded.
In the isolated group of localities, centered in the Bryansk Region, hybrids are more common than within the River Volga basin. Of six localities, which can be checked taxonomically by herbarium specimens, only hybrid specimens have been collected in two localities (Pod'yevotskaya Datscha and Prolysovo); in two localities, only non-hybrid individuals are known (Bryansk and Molodovoye); in two other localities (Krasnyi Rog and Rogovichi); both hybrid and non-hybrid individuals are at our disposal.
Thus, existing data give evidence of a wider introgression between C. macranthos and C. calceolus in Eastern Europe than reported previously. In this area, historical reports of C. × ventricosum are limited, being expressed by Khitrovo (1910) and then by Mayevskiy (1954Mayevskiy ( , 1964Mayevskiy ( , 2006Mayevskiy ( , 2014. Khitrovo (1910) was the first who has noted that at least some plants do not represent typical C. mac-ranthos plants by stating that «we were unable to collect enough material to recover the distribution of two varieties, established by Reichenbach: v. vulgare and v. ventricosum». At that time, the hybrid origin of C. × ventricosum was not universally accepted, and it was frequently treated as a variety of C. macranthos. The same taxonomic status was accepted by Nevski (1935) and even later (Smolyaninova, 1976, in subspecific rank), when the hybrid origin of C. × ventricosum became widely recognised. In more recent time, Averyanov (1999Averyanov ( , 2000 noted the presence of hybrids in two localities (Krasnyi Rog and Rogowichi), but simultaneous presence of both hybrid and non-hybrid individuals was interpreted by him as an evidence of the origin of these specimens from culture.
The distribution of hybrid and non-hybrid plants over time indicates a progressive replacement of nonhybrid plants by hybrids. In the isolated group of localities centered in the Bryansk Region, the last nonhybrid C. macranthos was collected in 1903. The present-day field investigation of the largest population has confirmed that only hybrids are extant, with no signs of non-hybrid C. macranthos individuals.
Cypripedium × ventricosum is easily distinguishable from C. macranthos by several morphological features, which are intermediate between its parents. One feature is the sparsely pubescent ovary (Fig. 2D,E,F,G,H,I,J) that is similar to that of C. calceolus, but the latter has even stronger pubescence. In contrast, the ovary of C. macranthos is always completely glabrous. Another characteristic feature is the narrowly ovate to broadly lanceolate shape of the median sepal, which is also intermediate between ovate to broadly ovate shape of C. macranthos, and lanceolate shape of C. calceolus. Then, hybrids are noticeable by the colour of the lip, which is not purely purple, but also has some visible yellowish colouration and (or) fragmentary whitish (Fig. 2B,C), but this cannot be examined on badly prepared or very old herbarium specimens. Lastly, C. × ventricosum is noticeable for its ability to form two-flowered inflorescences ( Fig. 2A), whereas stems of C. macranthos always bear only one flower. The herbarium specimens and all the modern photographs from the Bryansk Region, which are in possession of the authors, web-published (Ueda, 2021a) or used in the Red Data Books of the Bryansk Region (Bulokhov et al., 2016) and Red Data Books of the Belgorod Region (Prisnyi, 2005), are clearly attributable to hybrids either by colour, or by two-flowered stems, or by pubescent ovaries, or by a combination of these features, with no noticeable signs of non-hybrid plants. Historically, co-occurrence of C. macranthos / C. × ventricosum and C. calceolus was reported in localities near the villages of Prolysovo and Molodovoye (Khitrovo, 1910). In the largest extant population near the village Prolysovo, there are C. calceolus plants growing sideby-side with C. × ventricosum. Obviously, such co-occurrence provides substantial possibilities for hybridisation, which has recently most likely led to the final elimination of C. macranthos in this part of its range by absorption from the more common C. calceolus. It cannot be excluded that introgression may continue further, resulting in the further gradual elimination of the C. macranthos genotype due to the pressure from the more numerous C. calceolus.
The new finding of a large introgressive zone may be interpreted as a confirmation of Averyanov's hypothesis that this hybrid is a stage of the speciation process leading to a new bona fide species of hybrid origin. Some advantage of hybrid individuals in contrast to non-hybrid plants may be supposed. Thus, hybrid individuals may benefit from the present-day ecological conditions of the area, resulting that they have outlived parental C. macranthos, occurring there in the past.

Decline in the number of localities of Cypripedium macranthos in European Russia
Cypripedium macranthos displays a negative change throughout its natural range in Russia, namely in the Far East, Siberia, the Urals, and European Russia, which has been ascertained by the analysis of the years of recording with the data adjustment relative to the intensity of botanical exploration in the respected time intervals (Petr G. Efimov, unpublished). In the westernmost portion of the species range within European Russia, the decrease in the number of C. macranthos localities is especially pronounced, and it is selfevident from the dates of recording. The current study shows that the only place, where non-hybrid plants are still extant in European Russia, is a population in the Republic of Chuvashia, near the village Urakovo. It was last re-visited by Margarita M. Gafurova (pers. comm.) in 2008. About 30 clones were found with ca. 200 generative shoots and ca. 100 vegetative ones. The prospects of the plant preservation were estimated to be high (Margarita M. Gafurova, pers. comm.) as they are confined to a hardly accessible place on the crumbled slope, but the plants undoubtedly deserve a special protection.
The hybrid plants are also currently present only at one place, near the village of Prolysovo in the Navlya District of the Bryansk Region, where several populations are known. In the Bryansk Region C. macranthos / C. × ventricosum has similarly undergone a severe decline, being originally recorded in 5-6 districts and now only present in one. The solitary survived populations represent a large contrast with the historic data, which tell us about very numerous plants: «according to the data from local people, it is not rare, and occurs in a large number» (Zinger, 1886); «this orchid[…] is so numerous that serves as a common source for bouquets on the Trinity day» (Khitrovo, 1910). In the vicinity of the village Prolysovo, four populations have been confirmed in the last 20 years; the populations were  (Bulokhov et al., 2016). In the latter population, the number of stems decreased to 178 in 2021 according to regular studies of the species dynamics conducted by the Bryansk State University. Besides Navlya District, records in other districts of the Bryansk Region date back to 1903 and earlier times, and thus they are more than 100 years old.

Remarks about the Cypripedium guttatum distribution near its western distributional limit
In Russia, the distribution of C. guttatum protrudes further to the west compared to C. macranthos (Averyanov, 1999(Averyanov, , 2000Bulokhov et al., 2016), which is confirmed by numerous localities between the Ural Mountains and the Bryansk Region. In total, in European Russia, C. guttatum is known as many as from 23 of 44 regions. In six regions, only a solitary locality is known.
Similarly to C. macranthos, the presence of C. guttatum in Ukraine is doubtful. In both editions of the «Flora of Ukrainian SSR» (Kleopov, 1933;Bordzilovski, 1950), an assumption about possible finding of this species in the Chernigov Region of Ukraine is expressed, taking into account the neighbouring locality in the Bryansk Region of Russia. Other sources (Protopopova, 1987;Sobko, 1989;Mosyakin & Fedoronchuk, 1999) completely omit this species, with an exception of Smolyaninova (1976), who reported it from Ukraine again, but gave no details. Similarly to C. macranthos, Averyanov (1999Averyanov ( , 2000 expressed doubts about the presence of this spe-cies in the Ukrainian flora. Herbarium specimens from Ukraine, mentioned by Averyanov (1999Averyanov ( , 2000 from the villages of Rogowichi and Krasnyi Rog, do not belong to Ukraine, but to the Bryansk Region of Russia. Moreover, we have been unable to locate those specimens in herbarium LE. Therefore, it is possible that they were cited by mistake. There are two other herbarium samples from Ukraine, but both are very doubtful. They are the following: «Khar'kov Province, herb. N.K. Sredinsky» (LE 1107800!); «in montosis umbrosis ad «Catherinopolin' et alibi haud vulgaris» (LE 1107799!). The former is questionable because it belongs to Sredinsky's herbarium, which is notable for many odd and unconfirmed collections, including collections of Herminium monorchis (L.) R.Br. and Spiranthes spiralis (L.) Chevall. from the Crimea, which have never been confirmed (Privalova & Prokudin, 1959;Efimov et al., 2018). The label of the latter specimen is the same that was discussed earlier, under the name of C. macranthos; most likely, it is a collection made in the Ural Mountains, near Yekaterinburg.
In Belarus, all main floristic sources (Nevski, 1949;Kozlovskaya, 1978;Lebed'ko, 2017) report C. guttatum only for Mohilev Region, with the reference to Cholovsky (1882) who obviously provides the original data. Cholovsky (1882) reported the finding of this species near the village of Polynovichi in the surroundings of Mohilev. No herbarium specimens are known. It should be noted that Cholovsky's reports are sometimes questionable (Dmitry V. Geltman, pers. comm.), which means that the historic presence of this species in Belarus is unconfirmed.

Conclusions
Assembling primary data is an important task to provide more correct distributional data for the conservationally important and protected plant species. In the studied case, such analysis allows us to substantially clarify the distribution of the studied Cypripedium species in Eastern Europe, to distinguish between incorrect, doubtful and true localities, and to estimate the amount of the C. macranthos introgression with C. calceolus in Eastern Europe. The temporal analysis of the data has made it possible to define localities where plants persist up to now. It also gives evidence of a previously wider distribution of C. macranthos along the western frontiers of Russia and possibly in Ukraine and Belarus, too. The study of this type can be recommended for other species, especially for those, which are simultaneously rare, decreasing, and legally protected.
Cypripedium macranthos should be excluded from floristic lists and documents that establish protection of plants in the Bryansk Region, while C. × ventricosum should be included instead. Cypripedium × ventricosum also represents a conservationally important part of the local biodiversity. Taking into account that it remains as a relict, it is quickly decreasing and is often collected by people as an ornamental plant, in the Bryansk Region, C. × ventricosum deserves to be protected at the «critically endangered» category, which is facilitated by its presence in the Red Data Book of the Russian Federation (Bardunov & Novikov, 2008).
At the same time, findings of new, previously unknown localities of the discussed taxa in Eastern Europe are possible. Further findings in the Republic of Tatarstan in the area adjacent to the Republic of Bashkortostan are especially awaited in view of the very close-set localities in Asiatic Russia, e.g. in the Republic of Bashkortostan (Ueda, 2021c). Further findings of original material in localities classified here under the category «unconfirmed» are of utmost importance. Simultaneously, more attention should be paid to the determination of C. macranthos / C. × ventricosum plants from European Russia both in herbaria and under natural conditions.