Studies in Asian Nervilia (Orchidaceae) VII: Nervilia kasiensis, a new Lao endemic

Studies in Asian Nervilia (Orchidaceae) VII: Nervilia kasiensis, a new Lao endemic

S.W. Gale1, T. Phaxaysombath2

1 Kadoorie Farm and Botanic Garden, Lam Kam Road, Tai Po, New Territories, Hong Kong;

corresponding author e-mail: stephangale@kfbg.org.

2 Biodiversity and Ecology Institute, Ministry of Science and Technology, Vientiane, Laos PDR; e-mail: pthatsaphone@hotmail.com.

Abstract A new species belonging to the terrestrial orchid genus Nervilia is described from Kasi District, Vientiane Province, northern Laos. Referable to the widespread and species-rich N. adolphi/punctata alliance on account of its solitary flower, slender white and violet-marked labellum and glabrous, angular leaf, N. kasiensis is morphologically most closely allied to N. muratana of southern China and northern Vietnam. As in that species, the flowering and leafing phases overlap, an unusual feature among members of the genus. The new species can be distinguished from N. muratana by its shorter inflorescence, its weakly spreading perianth with beige sepals, its narrower labellum

with a central pubescent strip on the epichile, its arched column, and by its faintly tessellated leaf. A morphological description, line drawing and notes on the species’ ecology and conservation status are presented.

Description

Nervilia kasiensis S.W.Gale & Phaxaysombath, sp. nov. — Fig. 1, 2, 3

This new species most closely resembles N. muratana S.W.Gale & S.K.Wu in the outline of its labellum, in the shape of its leaf and in its non-hysteranthous growth habit. However, N. kasiensis is distinguished from N. muratana by its much shorter inflorescence (up to 4.3 cm in the former vs 6.5–10.0 cm in the latter), its weakly spreading perianth (vs widely spreading in the latter) with beige sepals (vs white in the latter), its narrower labellum (up to 6.4 mm wide in the former vs 9–12 mm wide in the latter) with a central pubescent strip on the epichile (vs shortly and sparsely hairy along the main veins in the latter), its arched column (vs straight in the latter), and by its tessellated leaf (vs uniformly dark green in the latter). — Type: Gale & Phaxaysombath HNL-KFBG 537b (holotype HNL, flowered in cultivation from Gale & Phaxaysombath HNL-KFBG 537a), ex cult. Biotechnology & Ecology Institute, Ministry of Science & Technology, Vientiane, Laos, 11 Mar. 2016; Gale & Phaxaysombath HNL-KFBG 537a (paratype HNL, leaf), Khoun Lang Cave, Kasi District, Vientiane Province, Laos, 29 Nov. 2015.

Etymology. Named after Kasi District, northern Laos, in which this species was discovered.

Glabrous terrestrial herb up to 12 cm tall. Tuber cream-white, ovoid-fusiform, 1.1–1.8 cm long, 0.6–1.2 cm wide, 3–4-noded, bearing a few stout, wiry, minutely hairy roots up to 1.3 cm long at the nodes. Subterranean stem emerging from apical or intermediate node of tuber, whitish brown, 2.1–6.7 cm long, 1.8–2.6 mm diam, many-noded, producing 2–3 segmented lateral runners up to c. 5.0 cm in length that each give rise to a daughter tuber at the apex. Petiole-like stalk light green, erect, (3.1–)8.5–10.2 cm long, 2.8–3.0 mm diam, sulcate, bearing 1 brown, fibrous, loosely sheathing cataphyll 1.9–2.3 cm long at base. Leaf blade dark green with bands of faint, iridescent silver-grey tessellation in between the main veins, held well above ground level, cordate-polygonal, with 7 main veins diverging palmately from the origin of the petiole-like stalk, slightly lobed at the tips of the main veins in some individuals, (4.5–)7.7–8.9 cm long, (4.2–)7.2–8.0 cm wide, deeply cordate at base, the basal lobes rounded, not overlapping, margin flat, apex acute. Inflorescence emerging while the plant is in leaf, erect, terminal, warty at base near junction with subterranean stem, terete above, 2.5–4.3 cm long to origin of floral bract, 2.0–2.2 mm diam, olive green flushed brown, bearing 1 short papery sterile bract at base and 1 sheathing cataphyll above; cataphyll olive green flushed brown with irregular purple blotches, 1.8–2.8 cm long, enclosing the base of the floral bract, apex acute; floral bract olive green with irregular purple blotches, narrowly elliptic, 4.8–5.5 mm long, 1.4–1.6 mm wide, exceeding the pedicel, apex acute. Flower solitary, resupinate, nodding, perianth not spreading widely; pedicel concealed within the base of the floral bract, up to 2.0 mm long; ovary narrowly conical, 4.9–5.2 mm long, c. 2.5 mm diam, olive green with irregular purple blotches; sepals and petals similar, outer surfaces cream-beige with irregular pink-violet flecks, glossy white inside, narrowly elliptic-lanceolate, acuminate; dorsal sepal 22.4–26.8 mm long, 3.5–4.2 mm wide, 5-veined; lateral sepals slightly oblique, slightly inflated and slightly saccate at base, 21.8–24.6 mm long, 2.8–3.5 mm wide, 3-veined; petals slightly oblique, 21.0–23.5 mm long, 1.8–2.8 mm wide, 3-veined; labellum white with irregular pink-violet flecks and blotches, not spurred but slightly concave at base, narrowly obovate-spathulate, 20.7–21.5 mm long, divided above the middle by a narrow waist into a hypochile and epichile; hypochile oblong, 11.2–12.0 mm long, 3.5–4.2 mm wide, lateral margins raised and embracing the column, terminating in a pair of short, ovate, obtuse auricles up to 0.4 mm long; epichile ovate-orbicular, 9.5–9.8 mm long, 5.9–6.4 mm wide, apex acute; disk bearing a central lanateband that divides in 2 below the auricles and then merges again at the base of the epichile to form a raised pubescent strip that terminates within 1.5 mm of the apex, shortly papillate elsewhere on the epichile. Column white, slender, clavate, arched towards the apex, 10.2–11.5 mm long, with a patch of short hairs below the stigma; anther cap helmet-shaped, c. 1.8 mm long; pollinia enclosed behind the stigma, 2.6–2.8 mm long; stigma shield-shaped, slightly concave; rostellum forming a prominent ridge along the apex of the stigma.

Distribution — At present known only from the type collection, which comes from fragmented primary hill forest in northern Laos (Fig. 3). Its discovery in similar habitats elsewhere in Laos as well as in neighbouring parts of Thailand and Vietnam might be expected, although primary forest in the region continues to dwindle rapidly.

Ecology — Nervilia kasiensis is an understorey herb that grows in shade in deep organic soils in moist, evergreen hill

forest over limestone at c. 750 m altitude. The flowering shoot emerges in March, while its tuber is still connected by a runner to the previous year’s leafy shoot. The old leaf withers and a new leaf emerges from a separate runner after anthesis. Multiple runners are produced both from nodes of the tuber itself and from the subterranean stem of leafy shoots. The presence of a prominent rostellum at the apex of the stigma (Fig. 2h) suggests that N. kasiensis is outcrossing (cf. Gale 2007).

Conservation status — Only a small population of fewer than ten emergent shoots was found at the type locality. The availability of suitable habitat throughout the Khoun Lang Nature Reserve offers hope that more plants occur nearby. However, on-going destruction of primary moist broadleaved forest in northern Laos, as well as in neighbouring parts of Indochina, indicates that this apparently restricted and rare species is under considerable threat due to habitat loss. Pending surveys to better gauge its distribution and abundance, N. kasiensis is for now considered Data Deficient (DD; IUCN 2012). Note — On account of its glabrous, angular leaf and the narrow, white and violet-marked labellum of its single flower, N. kasiensis is immediately recognisable as a member of the N. adolphi/punctata alliance. In addition to the characters noted in the diagnosis that differentiate it from N. muratana, its closest morphological ally, N. kasiensis is also distinguished by its relatively broader tepals as compared to those of that species. In its non-spreading perianth, the slightly concave base of its lip and the rounded hypochile auricles, N. kasiensis is also similar to N. alishanensis T.C.Hsu, S.W.Chung & C.M.Kuo, a species of Taiwan and Hainan Province in southeast China (Hsu et al. 2012, Gale et al. 2015). However, overall dimensions of the leaf and flower parts are otherwise markedly different, added to which N. alishanensis lacks a functional rostellum and is reported to be self-pollinating (Hsieh et al. 2013).

Fig. 1 Nervilia kasiensis S.W.Gale & Phaxaysombath. a. Plants in leaf at the type locality in northwest Laos showing the faint silver-grey mottling on the adaxial surface; b. plant in flower showing the non-hysteranthous growth habit; c. close-up of inflorescence; d. lateral view of flower showing slightly saccate base of the lateral sepals; e. front view of flower showing the weakly spreading perianth.

Fig. 2 Nervilia kasiensis S.W.Gale & Phaxaysombath. a. Plant in flower; b. plant in leaf with flowering shoots emerging from daughter tubers at the tip of lateral runners borne from the subterranean stem; c. labellum, flattened; d. dorsal sepal; e. lateral sepal; f. petal; g. lateral view of column; h. ventral view of column apex showing anther, rostellum and stigma; i. pollinia. — Drawn by S.W. Gale (a, c–i: Gale & Phaxaysombath HNL-KFBG 537b; b: Gale & Phaxaysombath HNL-KFBG 537a (both HNL)).

Soure: Blumea 62, 2017: 1–5 ISSN (Online) 2212-1676