Boesenbergia quangngaiensis N.S. Lý, 2017

Lý, Ng ọc-Sâm, 2017, Boesenbergia quangngaiensis (Zingiberaceae), a new species from Central Vietnam, Phytotaxa 324 (1), pp. 83-88 : 84-85

Boesenbergia quangngaiensis N.S. Lý sp. nov.

Similar to B. plicata Ridl. in the vegetative habit, plicate leaves, inflorescence habit, and anther crest absent but differs in the sessile or short–petiolate leaves, petiole 0.2–0.3 cm long (vs. longer, 10–13 cm long), broadly elliptic lamina with pubescence on both surfaces (vs. ovate and sparsely hairy beneath), shorter bracteoles, 2.8–3 cm long (vs. longer, 5–6 cm long), suborbicular to oblong obovate labellum with a deep red band at the centre, reddish-pink blotch at the tip (vs. oblong-obtuse, yellow with a cherry red band at the base, similarly coloured at the tip or a broad band the whole length of the tip), and ovary pubescent (vs. glabrous).

Type:— VIETNAM. Quảng Ngãi Province, Nghĩa Hành District, Hành Tín Ðông Commune, Trường Lệ Village, Mount Dầu, Nước Nổi stream, secondary evergreen broadleaf forest, 108°.80530’N, 12°.86156’E, 125 m elev., 12 April 2015, Ngọc-Sâm Lý, Lý-615 (holotype: VNM, isotype: P, VNM). Fig. 1 .

Evergreen, perennial, rhizomatous herb up to ca. 70 cm tall, forming small, loose clumps with 1–3(–4) leafy shoots per clump. Rhizome with numerous elements developing from the base of the previous element, oblong, 1.9–2.4 × 0.9–1.2 cm, externally red-purple when young and purple with age, internally with two concentric rings, the outer red-purple, inner cream yellow, non-aromatic, covered with red-purple, triangular scales, soon decaying; roots many, extending from the rhizome base, fleshy, 15–20 × 0.4–0.6 cm, externally cream yellow, internally white, covered in short root hairs along the full length, fibrous roots numerous. Pseudostems usually 2–3, increasing in number each season, up to ca. 15 cm long, 1.1–1.3 cm diam., reddish at base, distally light green, glabrous, with 2(–3) leafless sheaths, 3.3–11.5 × 2–3 cm, conspicuously longitudinally striate, red-purple at base, distally tinged greenish, sparsely pubescent, margins hyaline. Leaves (2–)3–4, arranged distichously, upper two nearly opposite; leafy sheaths 11.2–16.5 cm long, conspicuously longitudinally striate, covered in part by the leafless sheath, light green, glabrescent, margin opaque whitish-green, sparsely pubescent; ligule deeply bilobed, lobes ovate, 1.5–1.8(–2) × 0.6–0.8 cm, opaque white, sparsely pubescent, apex acute; petiole absent or 2–3 mm long, light green; lamina elliptic, sometimes asymmetrical, 25–35.6 × 7.5–9 cm, base attenuate, usually unequal, apex short acuminate, adaxially light green, somewhat shiny, veins prominent, sparsely hairy with long white hairs, abaxially glaucous, greenish, sunken between the veins, sparsely hairy with long white hairs. Inflorescence terminal, basal third to half clasped between the leaf sheaths, apical ⅔ to ½ exposed, 9.3–13.7 cm long; peduncle short, 0.8–1.3 × 0.4–0.6 cm, white, glabrous; spike lanceolate [narrowly ovate], 8.5–12 cm long, ca. 1 cm at the widest point, longitudinally furrowed on the flowering side; sterile bracts 1–2, narrowly ovate, 3–8.3 cm long, 0.7–1.5 cm at widest point, greenish, margins translucent white, sparsely pubescent, apex mucronate with a short mucro ca. 2 mm long; bracts 13–20 per each spike, alternately 2-ranked from the top to the base, the bracts in each rank about 0.4–1 cm apart, facing one way, narrowly ovate, open to the base, 30–32 mm long, 8–9 mm at widest point, pale dull green-white, sparsely pubescent, each with a single bracteole and a single flower, the rachis stout, exposed on the non-flowering side; bracteoles narrowly ovate, 28–30 × 7–9 mm, tinged pale brown-green, externally sparsely pubescent, open to the base, on the opposite side of the floral tube from the bract, apex attenuate, tip mucronate with a short mucro 1.5–2 mm, margins overlapping and fully enclosing the floral tube. Flowers usually equal to number of the bracts, 1(–2) flower open at a time, 4.8–5.2 cm long, flowering sequence from the apex downward, labellum orientated ca. 75˚ to the bract apex; calyx tubular, 5–6 × 1.5–1.7 mm, white, externally sparsely pubescent, incision ca. 2 mm down one side, apex with 3 inconspicuous, short, rounded lobes; floral tube 25–28 mm long, ca. 2.5 mm diam. at widest point at the apex, widening gradually towards apex, white, glabrous; dorsal corolla lobe oblong, 13–14 × 4–6 mm, slightly convex, revolute, white, glabrous, apex cucullate; lateral corolla lobes 11–13 × 4–5 mm, oblong, slightly convex, revolute, white, glabrous, apex slightly cucullate; androecial cup ca. 3 mm long, ca. 3 mm wide, orientated ca. 100˚ to the floral tube, externally with glandular hairs, internally bright red at part connected to the labellum; labellum suborbicular or broadly obovate, 2–2.1 × 1.8–1.9 cm, the basal part with sides up curved and overlapping the staminodes, the broad apex spreading, pure white to pale greenish-white, centrally with deep red band at the base, extending to upper third, apical reddish-pink coloured patch in the middle, densely glandular hairs at both sides, apex emarginate, slightly undulate, deflexed outward; lateral staminodes obovate, 10–13 × 5–6 mm, pure white or tinted lemon-yellowish white, slightly reflexed upward, dense, glandular hairs, apex round or truncate. Stamen 10–14 mm long; filament 5–8 × 2–2.5 mm, white, sparse, short hairs; anther 6–7 × ca. 2 mm, connective tissue with glandular hairs; anther thecae ca. 6–7 × ca. 1 mm (each), dehiscent throughout their full length, white; anther crest absent; pollen white. Ovary cylindrical, ca. 2 × 2 mm, trilocular, white with reddish tint at apex, sparsely pubescent; style filiform, ca. 4.5 cm long, white; stigma shallowly cup-shaped, ca. 0.6 × 0.8 mm, white, ostiole circular, without cilia; epigynous glands 2, linear, 3.5–4 mm long, ca. 0.5 mm wide, cream. Fruit a capsule, oblong-ovoid, 1.2–1.3 cm long, ca. 0.5 cm diam., mature fruit green, with 2–3(–4) seeds. Seed lanceolate, 11–13 mm long, 1.5–2 mm in diam., brown, hairy; aril translucent white, 3–5 mm long, linear to lacinate.

Phenology: — Boesenbergia quangngaiensis was observed in flower in March–July, and fruit in April–August.

Distribution, ecology and conservation status: — So far known only from two districts within Quảng Ngãi province. At the type locality (Nghĩa Hành District) Boesenbergia quangngaiensis grows near streams and shady areas of hillside in secondary evergreen broadleaf forest dominated by dipterocarps in Mount Dầu (125–4573 m elev.). In Tây Trà District it is so far known to occur in lower primary evergreen broad-leaved tropical forest on Mount Cà Ðam (about 732–872 m elev.). The new species retains leafy sheathes with leaves throughout the year (perennial herbs) which differs from the other four in Vietnam which are annual herbs ( B. siphonantha is annual at its locality in the Andaman Is).The two localities are distanced about 60 km from each other. Currently only about 20 sub-populations which together consists of about 100 mature clumps in a total Area of Occupancy of less than 6.5 km 2 on Mount Dầu, and 10 sub-populations which together consists of about 500 mature clumps in a total Area of Occupancy of about 18 km 2 on Mount Cà Ðam were observed. Although both localities have a certain degree of legal protection by the local board of the Khánh Giang–Trường Lệ community forest and the Department of forest protection in Tây Trà and Trà Bồng Districts and no uses were reported by the local people the species still faces some at risk due to loss of the habitat within its range (in particular the clearing of forest land for Acacia Mill. (1754: 25) plantations). It is expected that this species will be reported from other localities in near future. Based on currently available data we therefore provisionally assess this species as Endangered (EN B2 a,b (ii,iii)) according to the IUCN Red list criteria ( IUCN, 2012). Further exploration of the area around Mount Dầu and Mount Cà Ðam is necessary to fully assess the conservation status.

Etymology: — The specific epithet refers to the geographical locality, Quảng Ngãi Province, where the species was discovered.

Additional specimens examined: — VIETNAM. Qu ảng Ngãi Province , Nghĩa Hành District , Hành Tín Ðông Commune, Trư ờng Lệ Village, Mount D ầu, Đá Bông hill, secondary evergreen broad-leaved forest, 14°51.56’N, 108°49.28’E, 573 m elev., 12 April 2015, Ng ọc-Sâm Lý, Lý-614 (VNM) ; the same locality, Nư ớc Nổi stream, Mount D ầu, 14°53.76’N, 108°48.24’E, 497 m elev., 12 April 2015, Ng ọc-Sâm Lý, Lý-613 ( VNM!) ; the same locality, Nh ự hill, 14°52.06’N, 108°48.74’E, 317 m elev., 13 April 2015, Ng ọc-Sâm Lý, Lý-516 (VNM) ; the same locality, Nư ớc Nổi stream, 108.80530°N, 12.86156°E, 125 m elev., 9 April 2010, Ng ọc-Sâm Lý, Lý-474 (Paratypes: VNM!, E!, SING!). Tây Trà District , Trà Trung Commune , Mount Cà Ðam , Nư ớc Bi ếc stream, lower primary evergreen broad-leaved tropical forest, 15°09.252’N, 108°27.452’E, 872 m elev., 28 July 2016, Ng ọc-Sâm, Lý-753 (VNM) ; the same locality, 15°08.988’N, 108°27.794’ E, 732 m elev., 28 July 2016, Ng ọc-Sâm Lý, Lý-774 (VNM) .

Notes: — This discovery raises the number of Boesenbergia species to six in Vietnam. Of these, B. phyllostachya (Gagnep.) K. Larsen (1997: 363) and B. quangngaiensis are endemic while the four remaining species have also been reported from neighbouring countries, e.g., B. petiolata Sirirugsa (1987: 423) ( Thailand, Lao P.D.R.), B. xiphostachya (Gagnep.) Loes. (1930: 568) (Lao P.D.R., Thailand), B. siphonantha (King ex Baker) M. Sabu, Prasanthk. & Škorničk. ( India, Thailand), and B. rotunda (L. (1753: 2)) Mansf. (1958: 239) ( Cambodia, China, Lao P.D.R., Thailand). Considering the morphology of these species, vegetatively, B. siphonantha is acaulescent and produces either radical inflorescence from the rhizome near the stem base or a terminal inflorescence between the leaf sheaths while the other five are caulescent. Moreover, in the species with a terminal inflorescence, B. petiolata and B. rotunda have a spike clasped by the uppermost leaf sheaths while B. phyllostachya , B. quangngaiensis , and B. xiphostachya produce an elongated spike, mostly exserted from the leaf sheaths. The extent of Boesenbergia diversity in Vietnam is still poorly understood. Future fieldwork should help to provide a better understanding of these and perhaps several more new taxa.

Figures

FIGURE 1. Boesenbergia quangngaiensis. A. Plant in natural habit; B. Mature plant with flower; C. Basal part of the plant with roots, rhizome cross-section of rhizome; D. Ligules in front and side views; E. Close-up of the flower; F. Inflorescence with flower in natural habit; G. Inflorescence with sterile bract and flower; H. Dissection of flower (from left): Flower, bract, bracteole, calyx, dorsal and ventral corolla lobes, lateral staminodes (above), labellum, and floral tube with ovary, calyx, and stamen attached (side view) (scale bar in cm); I. Detail of ovary with epigynous glands and anthers in side, front and back views (scale bar in mm); J. Mature fruit (below) and seeds (above) (scale bar in mm).—Photos by Ngọc-Sâm Lý.