The genus Cypripedium ( Orchidaceae ) in the flora of Vietnam

The genus Cypripedium includes 40–45 species distributed mainly in areas of Holarctic region with temperate climate. Its highest species diversity is observed in the eastern part of mainland Asia and in Northern America. In intact habitats, some species of this genus are quite common playing significant role in plant communities forming picturesque landscape aspects during anthesis. Some Cypripedium species are not uncommon in uplands and mountains of subtropical countries, but few of them reach tropical zone. In Central America these are Cypripedium irapeanum, C. molle and C. dickinsonianum distributed from Mexico to Guatemala, Salvador and Honduras. In Asia only two species – Cypripedium lentiginosum and C. subtropicum, reported in the paper, reach truly tropical zone. Localities of these species recently discovered in northern Vietnam represent southernmost locations of the genus area in the Old World. A brief taxonomical review of two discovered species in the flora of Vietnam is presented in the paper. The treatment includes key for species identification; standard taxonomic citations for the genus, sections, species and synonyms; data on types and their locations; available information on ecology, phenology and distribution, expected IUCN Red List status; notes on phylogeny, taxonomy, geography and possible conservation actions, as well as the list of studied specimens and relevant materials.


Cypripedium
Notes.Distribution of this species is amazing for its striking disjunctions.The plant is known presently only in three miserable locations forming a triangle with arms approximately 1200 ×1200 × 300 km (Fig. 3A).Though its formal area of occurrence is relatively large, the actual area of occupancy in fact is negligibly small.Additionally, all known populations are strongly depleted presently by commercial collecting and lose almost all mature, flowering size individuals.The last assessment estimates this species as Endangered [B2ab(ii,iii,v); C2a(i)] (Rankou, Averyanov, 2014b).However, plant certainly comes fast to full extinction due to  overcollecting in all known locations.Additional field studies and botanical explorations in areas of the species occurrence may be recommended for discovery and effective protection of probably still existing new subpopulations.
The record of C. subtropicum in Sin Ho district of Lai Chau province of northwestern Vietnam presented here is new for the flora of the country.Early record in northern Vietnam in Ha Giang province is based on literature data (Jiang, Liu, 2009).Description of C. singchii (Liu, Chen, 2009) is based on material collected in the same place and probably from the same population (Jiang, Liu, 2009).
The general habit, many flowered inflorescence and small, filament-like staminode indicate very primitive character of this species, which is definitely much closer to Cypripedium ancestors than any other its congeners.It may be related solely to C. wardii Rolfe from eastern Tibet and western Yunnan.Both species form taxonomically very isolated group segregated in rank of separated section (Cribb, 1997;Eccarius, 2009) supported by molecular studies (Li et al., 2011).Expected relations of this section to American Selenipedilum Pfitzer or Cypripedium irapeanum La Llave et Lex.(Chen, Lang, 1986)  Notes.The last assessment estimates this species as Endangered [B1ab(ii,iii,v)+2ab(ii,iii,v); C2a(i); D] (Rankou, Averyanov, 2014a).However, expected area of the species occupancy as 20 km 2 looks certainly overestimated and in fact it is much smaller.Actually, years ago it was recorded from three locations only (Cribb, Chen, 1999;Chen, Liu, 2004;Chen, Cribb, 2005).Since the assessment in 2014, no information about any extant populations of this extremely rare plant became available.It is highly probably that the species is presently extinct, or stands on the verge of full extinction in the nature.Commercial collecting of the species for horticultural purposes, as well as for regional and Turczaninowia 20 (1): 118-124 (2017) international trade depletes its populations even in officially protected areas.
The species is one of the most sensitive elements of primary open limestone forests and scrub associated with a specific set of habitat conditions, such as rocky high elevations, nutrient availability, mossy steep slopes and permanent humidity.Such forests are critically endangered in the area and occupy presently miserable table-like summits of karstic remnant limestone hills or ridges surrounded typically by vertical cliffs.This unique kind of vegetation composed with many aboriginal species disappears very fast due to timber exploitation, forest fires, urbanization, soil erosion and climate drought connected with wide deforestation.
Botanical exploration in the species area can discover more extant population of this rare species.Their assessment and organization of effective protection can prevent coming extinction of this plant in nature.
Studied specimens.In fact, species is known solely by type specimens of C. lentiginosum, C. daweishanense and C. malipoense, as well as by few photographs made in the nature by local peoples and originated supposedly from the state China-Vietnam border area hardly accessible for scientific exploration.

Fig. 1 .
Fig. 1.A-C -Landscape and natural habitats of Cypripedium subtropicum in Lai Chau province of northwestern Vietnam.D-F -Plants of C. subtropicum in natural habitats in the same location (L.Averyanov et al., CPC 8243a).Photos of L. Averyanov and K. S. Nguyen.
Averyanov L. V. et al.Cypripedium in the flora of Vietnam Cribb et S. C. Chen and C. subtropicum S. C. Chen et K. Y. Lang, reported in this paper, reach truly tropical zone.Localities of these species recently discovered in northern Vietnam represent southernmost locations of the genus area in the Old World.