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 confirming 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. macranthos 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.