Panax vietnamensis Ha & Grushvitzky var. langbianensis N.V. Duy, V.T Tran & L.N. Trieu, 2016

Duy, Nong Van, Trieu, Le Ngoc, Chinh, Nguyen Duy & Tran, Van Tien, 2016, A new variety of Panax (Araliaceae) from Lam Vien Plateau, Vietnam and its molecular evidence, Phytotaxa 277 (1), pp. 47-58 : 53-55

Panax vietnamensis Ha & Grushvitzky var. langbianensis N.V. Duy, V.T Tran & L.N. Trieu , var. nov. ( Figs. 3 ; 4 & 5 )

A Panace vietnamensi Ha & Grushvitzky var. vietnamensi et var. fuscidisco Komatsu, Shu & Cai , foliolorum apicis brevioribus (<1cm), basibus aliquando attenuatis, pedicellis quoque brevioribus (≤ 0.6cm) atque petalis (≤ 1.4 cm longis), disco propminenti et styli saepius 2 praecique differt.

TYPE:— VIETNAM. Lam Dong Province: Lac Duong District, Xa Lat Community, Lang Bian mountain , elevation 1879 m asl, 12 º 02’6.54’’N, 108 º 26’02.78’’E, May 2010, N.V. Duy & V.T. Tran 520 (( holotype: VTN! ; isotype: DLU! ).

Perennial herb, 50–90 cm high. Rhizome resembling that of bamboo, creeping horizontally, 1–2.5 cm diam., the nodes very closely spaced, internodes 2–5 mm, outer surface yellowish-brown. Fleshy roots attached below rhizome, lumpy, spindle-shaped or subconic, 3–5 cm long, 2–4 cm in diam. Stem erect, slender, green, glabrous, with a spongy core. Leaves 3 or 4, rarely 5, palmately compound, verticillate at the top of stem; petiole 8–13 cm, glabrous, without stipules or stipule-like appendages; leaflets generally 5 (rarely 7), the three large leaflets almost the same size, blades membranous, ovate or elliptic, 10–12 x 4–5 cm, the proximal pair of leaflets much smaller, ovate-elliptic, 4–5 x 2–3 cm, secondary veins 5-8 pairs, conspicuous bristles present along the veins on both surfaces, base cuneate or attenuate, margin regularly serrate, rare doubly serrate, apex short caudate-acuminate for ca. 8 mm long; petiolule 8–11 mm long. Inflorescence an umbel of 40–80 flowers; peduncle 10–18 cm long, densely papilose and finely glandular; flowers 1.5–2 mm in diam.; pedicels 0.4–0.6 cm long, densely and finely glandular papilose; receptacle cup-shaped. Sepals 5, triangular, 0.45–0.55 mm long, glabrous. Petals 5, obovate, ca. 1.4 x 0.75 mm, glabrous. Stamens 5, 0.7–0.8 x 0.3–0.4 mm, filaments as long as or shorter than petals. Disk at first slightly convex and green, turning prominent and whiteyellow later. Ovary ca. 1 mm long; styles 2 (rarely 1), 0.6–0.8 mm long. Fruit ovoid, applanate, 4–5 mm in diam. Seed 1 (rare 2), compressed, ovoid, 3.5–4.5 x 3–4 mm.

Etymology:— The specific epithet refers to the type locality, Lang Bian Mountain, Lac Duong District, Lam Dong Province, Vietnam.

Phenology:— Panax vietnamensis var. langbianensis was observed to be flowering period that extends from May to June and fruiting from July to October.

Distribution, Habitat, Conservation status:— Panax vietnamensis var. langbianensis is endemic to the Lam Vien plateau, Lam Dong province in southern Vietnam, and is known only from that locality. It grows in small populations scattered on the floor of closed primary evergreen broad-leaved forest on slopes at high elevations (1879–1900 m a.l.s). Associated species at the type locality include Quercus langbianensis Hickel & Camus ( Fagaceae ), Litsea verticillata Vidal ( Lauraceae ), Manglietia conifera Dandy ( Magnoliaceae ), and Elaeocarpus sp. ( Elaeocarpaceae ).

Panax vietnamensis var. langbianensis has an area of occupancy (AOO) of only 1 km 2 and constitutes a single locality that suffers from some serious threats, including the clearance and the overexploitation of its rhizome for its herbal and pharmaceutical properties, which has let to its continuing decline both its distribution in the area, and habitat. Moreover, the population size with small number of mature individuals comprises only about two hundred, and from an estimated continuing decline of at least <50% of mature individuals over the first decade of the 21 th century in the largest subpopulation. Therefore, it should be probability of extinction in the wild of at least 50% in 10 years, and as such should be regarded as critically endangered (CBB2acb (ii,iii,v); C2a(i); E according to IUCN Red List Categories and criteria (IUCN 2010)).

Additional specimens examined (Paratype):— Vietnam. Lam Dong Province: Lac Duong District, Lang Bian Mountain , no date, Tixier s.n. ( P03258523 !) .

Figures

FIGURE 3. Panax vietnamensis var. langbianensis. A. rhizome; B. stem; C. three large leaflets; D. proximal pair of leaflets; E. pedicel; F–G. flowers; G. petal; I. disk and styles; J. stamen; J. fruit. Drawn by V.T. Tran from the holotype.

FIGURE 4. Panax vietnamensis var. langbianensis. A. habitat; B–C. stem and leaflets with umbel flower; D. rhizome; E. umbelliform inflorescence; F. H–I. flowers; G. pedicel; J. petal; K. disk and styles; L. stamen; M. fruit. Photo by N.V. Duy from the type locality.

FIGURE 5. Panax vietnamensis var. vietnamensis. A. leaflets; B. leaflet margin with double serrate. C. Petiole. D. flowers disk. Panax vietnamensis var.fuscidiscus.E.Leaflets;F.leaflet margin with serrate; G.Petiole; H.flowers disk.Panax vietnamensis var.langbianensis). I. Leaflets; J. leaflet margin with serrate; K. Petiole; L. flower disk. Photo by V.T. Tran.