Habenaria yachangensis Z.B. Zhang & W. Guo, 2015

Zhang, Zibin, Yang, Mei, Cai, Shuwei, Huang, Bogao, Wei, Yanqing, Chen, Qiaoqiao & Zhao, Xiuhai, 2015, A new species of Habenaria (Orchidaceae) from Guangxi, China, Phytotaxa 192 (2), pp. 112-116 : 112-115

Habenaria yachangensis Z.B. Zhang & W. Guo , sp. nov. ( Figs. 1 & 2 )

Type: — CHINA. Guangxi: Leye County, Yachang Orchid National Nature Reserve, elevation ca. 560 m, 3 September 2013, Xiao-hua Jin & Zi-bin Zhang 13814 (holotype PE!).

Habenaria yachangensis is similar to H. malintana ( Blanco 1837: 642) Merrill (1918: 112) by presenting adaxially light green, abaxially greenish silver leaves spiralling along the stem, densely flowered inflorescence, glabrous flowers pale green to greenish white with white towards the centre, but can be distinguished from the latter by having pale green to greenish white flowers with white towards the centre, a distinctly tripartite dorsal sepal, lateral sepals with 1 ‒ 2 teeth on one side (absent in H. malintana ), and petals with two thickenings on both sides and spur 13–35 mm (versus 2–8 or no spur).

Terrestrial. Tuber ellipsoid, 2.1–4.0 cm long, 1.5–2.5 cm in diam. Stem erect, terete, 16–45 cm tall, 2.5–4.0 mm in diam. Cataphylls 1–3. Leaves 3–6, alternate, basally sheathing, lanceolate, elliptic or obovate, 6–15 × 3.5–5.0 cm, marginally ciliate, adaxially light green, abaxially greenish silver, apex acuminate, mucronate; apically grading into the sterile bracts. Inflorescence 18–30 cm long, densely 8 ‒ 15-flowered; peduncle 14–25 cm long; sterile bracts 4 ‒ 8, sheath-like, spiral, basally adpressed to the stem, lanceolate to ovate-lanceolate, 1.5–3.2 × 0.5–0.8 cm, marginally ciliate, acuminate; rachis length 1–1.3 mm; floral bracts lanceolate, longer than or equalling the pedicel and ovary, 2.0–2.4 × 1.0–2.0 mm, glabrous, acuminate, decreasing in size toward the inflorescence apex. Flowers glabrous, pale green to greenish white with white towards the centre; ovary spreading from the rachis, straight or slightly arched, 1.2–1.6 cm long; dorsal sepal ovate-lanceolate, distinctly tripartite, 1.5–2.5 × 1.0– 1.5 mm; lateral sepals ovate-lanceolate, concave, with 1 ‒ 2 teeth on their front margin but otherwise entire-edged, 3.0–3.7 × 0.8–1.2 mm; petals ovate-lanceolate, 2.8–3.7 × 0.6–1.0 mm, concave, with two lateral thickenings approximately half-way along their length; lip tripartite, whitish green or white at the base, whitish green toward the apex of the lobes; mid-lobe linear-lanceolate, turned upwards, slightly curved backwards, 6.0–6.4 × 1.5–2.5 mm; side lobes linear-lanceolate, spreading, curved upwards, 3.4–3.8 × 0.8–1.2 mm; spur pale green with whitish green basal part, pendent, slightly clavate, almost entirely straight, longer than or slightly shorter than the ovary, very variable in length from 12 mm to 35 mm, apex obtuse; pollinia 2, sectile, 1.8–2.1 mm; anther erect, anther canals 1.6–3.2 mm long.

Distribution: Habenaria yachangensis has an extremely narrow distribution. Only a single population with about 30 plants was discovered in the Yachang Orchid National Nature Reserve of western Guangxi, China.

Phenology: Flowering occurs from August to September, and fruiting from September to October.

Habitat, ecology and phenology: Habenaria yachangensis occurs in primary subtropical evergreen forests at an elevation of ca. 560 m, and grows with Quercus bungeana Forbes (1884 : 83,85), Wendlandia uvariifolia Hance (1870: 73) , Phyllanthus emblica Linnaeus (1753: 982) and Imperata cylindrica Raeuschel (1797: 89) . Other orchids found in the area are Geodorum eulophioides Schlechter (1921: 70) and Geodorum densiflorum ( Lamarck 1792: 516) Schlechter (1919: 259) .

Etymology: The species is named after the type locality, Yachang Orchid National Nature Reserve, Leye County, Guangxi, China.

Similar species: Habenaria yachangensis is similar to H. malintana and H. finetiana Schlechter (1919: 126) . The diagnostic characters of the new species and its similar species are listed in Table 1.

Acknowledgments

The authors are grateful to Dr. Xiao-Hua Jin for his critical review of the manuscript, to Mr. Yun-Xi Zhu for the line drawing and to Mr. Wei Guo for advice regarding nomenclature. We also appreciate the financial support of 12th fiveyear National Science and Technology plan of China (2012BAD22B0203) and the Forestry Scientific and Technical Programs by Forestry Department of Guangxi Zhuang Autonomous Region of China (No. 2014-13).

Figures

FIGURE 1. Habenaria yachangensis Z.B.Zhang & W.Guo. A. Habit. B,C. Flower in back and in front view. D. Flower in side view.E. Lip and column in side view. F. Longitudinal section through lip and column. G. Flower in front view. H. Sepals and petals. I. Pollinaria.

FIGURE 2. Habenaria yachangensis Z.B.Zhang & W.Guo. A. Habit. B. Roots and tubers. C. Raceme. D. Flower in front view, showing the lip. E. Column. F. Flower in side view (sepals and petals removed). G. Flower parts, inner view: 1. dorsal sepal; 2,6. petals; 3,5. lateral sepals; 4. lip; 7. spur; H. Flower parts, outer view: 1. dorsal sepal; 2,6. petals; 3,5. lateral sepals; 4. lip; 7. spur.