Variations of Paphiopedilum callosum in VietnamPaphiopedilum callosum in Eastern Indochina belongs to typical herbaceous elements of broad-leaved, evergreen, warm-loving, lowland and submontane pristine forests. The species commonly grows here at elevations of 300-1000m (1000-3200 ft).
The habitats and natural conditions of this species in Vietnam were described earlier (Averyanov et al., 2003, 2004). This species was fairly common in lowland and hilly areas of southern Vietnam, before wide land reclamation and deforestation.
Regrettably, this species has become very rare, with nearly all its known populations seriously depleted by widespread commercial collecting. Growing at relatively low elevations, it is much more endangered than slipper orchid species occurring at higher elevations, where preservation of primary forests is usually better. Recent field explorations discovered a number of new populations of this rare species in remote regions of the country not previously explored. These investigations, as well as studies of numerous plants collected in Cambodia and Laos along the Vietnamese border, reveal remarkable variation of P. callosum, and make it possible to recognize at least three races in taxonomic rank of varieties. The key for their identification and a short illustrated survey of these intraspecific taxa in the flora of Vietnam are presented below.
Paphiopedilum callosum (Reichenb.f.) Stein, 1892, Orchideenbuch: 457 - Cypripedium callosum Reichenb.f., 1886, Gard. Chron., 2 Ser., 26: 326.
Type: Thailand, Regnier s.n. (Holotype – W).
Key for Identification of P. callosum Varieties found in Vietnam
1. Petals strongly sigmoid, distinctly down deflexed, usually more than 5 cm long,
1. P. callosum var. callosum.
P. callosum var. angustipetalum Guillaumin, 1924, Bull. Soc. Bot. France, 4 Ser., 24: 551.
Type: Cambodia, Geoffrey, 338 (Holotype – P). P. amabile auct. non Hallier f.: Guillaumin, 1937, Bull. Mus. Paris, 2 Ser., 9: 217; id., 1961, ibid., 2 Ser., 33, 3: 333; Gagnep., 1950, Bull. Mus. Hist. Nat. Paris, 2 Ser., 22, 5: 628; Seidenf., 1975, Contrib. Revis. Orch. Fl. Cambod. Laos Vietnam: 88; Aver., 1988, Prelim. List Vietnam. Orch. 2: 31; Pham Hoang Ho, 2000, Ill. Fl. Viet. 3: 762.
This is the most widespread and common race in Eastern Indochina, including southern Vietnam (map 1). Closed forests on steep rocky stream slopes are the most common habitat of this variety. Different kinds of tall bamboo are a common component of shrubby stratum in such forests, particularly on very steep slopes and rocky bluffs (fig. 1, 2). Granite and sandstone are the usual parental rocks in habitats of P. callosum var. callosum in studied areas. In intact populations plants often form a continuous cover with many hundreds of large clumps. Usually they grow as terrestrial clumps of clustering herbs on rich soils covered with more or less thick leaf litter (fig. 3-5); a few individuals were occasionally observed growing as lithophytes on shady mossy boulders. In their natural habitats plants flower in May-June (fig. 4) and develop fruits in November- December (fig. 5). Observed variation of coloration, shape and size of flowers in populations of P. callosum var. callosum is very wide. Plants in most studied colonies have large flowers with strongly deflexed, more or less heavily spotted, petals that are distinctly warty along upper and lower margins (fig. 6-8). Flowers of other plants petals bear few spots and barely pronounced warts on the lower margin (fig. 9, 10). Sometimes such plants with this feature closely approach P. callosum var. warnerianum. Some plants in natural populations of P. callosum var. callosum exhibit a tendency towards albinistic forms. Occasionally such plants lack only a part of purple pigments (fig. 11), but in some rare forms anthocyanins are completely absent (fig. 12). Similar forms are known in cultivation under the names var. sanderae (Hort.) Braem and var. viridiflorum (Hort.) Pfitzer. (Averyanov et al., 2003).
2. P. callosum var. warnerianum (T. Moore) P.J. Cribb ex Aver., comb. nov.
— Cypripedium barbatum var. warnerianum T. Moore, 1878, Warner Select. Orchid., 3 Ser., Pl. 3, t. 11.
Lectotype: T. Moore, 1878, l.c. Pl. 3, t. 11 (Cribb, 1998, p. 337). Cypripedium callosum var. sublaeve Reichenb.f., 1888, Gard. Chron., 3 Ser., 3: 331. -Paphiopedilum callosum subsp. sublaeve (Reichenb.f.) Fowlie, 1972, Orchid Dig. 36: 145. - P. sublaeve (Reichenb.f.) Fowlie, 1979, Orchid Dig. 43: 22. - P. callosum var. sublaeve (Reichenb.f.) P.J.Cribb, 1987, Gen. Paphiopedilum: 188.
Type: Thailand, cult. Measures s.n. (Holotype – W). Paphiopedilum thailandense Fowlie, 1979, Orchid. Dig. 43:220, nom. nud.
3. P. callosum var. potentianum (O.Gruss et J.Roeth) P.J. Cribb, 1998, Gen.
Paphiopedilum, ed. 2: 337. – P. potentianum O. Gruss et J. Roeth, 1995, Caesiana 5: 39.
Type: Thailand, cult. E. et G. Potent, Roth s.n. (Holotype – HAL).
This variety was described based on plants imported from Thailand without indication of their exact origin. This gives no guarantee that the plants were really collected on the territory of Thailand, which imports many plants from neighboring countries. In Vietnam very similar plants were found in lowland warm-growing forests of Cambodian type near the Cambodian border (map 1). Such a finding may indirectly indicate lowland areas of Cambodia and southern Laos as a possible area of distribution of this very rare taxon. Like both previous varieties, plants of P. callosum var. potentianum also demonstrate certain trends towards formation of sub-albinistic forms with a deficit of purple pigments. Some of these produce flowers of particular elegance (fig. 19).
On the basis of our observations, it looks as if these varieties merge into one another with more or less numerous intermediate forms. The understanding of their nature obviously needs more field studies of wild intact populations. Such study is urgently needed because survival of these varieties in nature is uncertain and the prospect for the continued existence of this lowland species, in the wild, is very bleak due to the rapid transformation of lowland areas for agriculture and economic development zones. The best hope is that some of these plants will be collected for cultivation before all become extinct.
Field and laboratory studies, results of which are presented in this paper, were made under the auspices of these exploration programs: "Population studies of endemic Paphiopedilum species in northern Vietnam" American Orchid Society, 2001-2002; "Discovery of endemic orchid flora in remote limestone areas of Northern Vietnam" American Orchid Society, 2004; “Exploration of rocky limestone flora and vegetation in Bac Kan province, northern Vietnam” U.S.A. National Geographic Society, 2004, # 7577-04; and investigation program of Vietnamese Botanical Conservation Program supported from Henry Luce Foundation (U.S.A.).
Averyanov L., Cribb, P., Loc, P. K., and N. T. Hiep. 2003. Slipper Orchids of Vietnam. With an Introduction to the Flora of Vietnam. Royal Botanic Gardens, Kew. Compass Press Limited.
Averyanov, L.V., Loc, P. K., Hiep, N. T., and D. K. Harder. 2003. Phytogeographic review of Vietnam and adjacent areas of Eastern Indochina. Komarovia. 3:1-83.
Averyanov L., Cribb, P, Loc, P. K., and N. T. Hiep. 2004. Lan Hai Viet Nam. Giao Thong van tai Publishing house. Ho Chi Minh City (Vietnamese ed., 2003). Cribb P. 1998. The Genus Paphiopedilum. Natural History Publications (Borneo) & Royal Botanic Gardens, Kew.
Leonid V. Averyanov
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