Cleisostoma luopingense Q. Liu & X.F Wu, 2021

Wu, Xun-Feng, Wang, Yu-Qian, Chi, Kuan-Bo, Liu, Qiang & Wang, Wen-Hua, 2021, Cleisostoma luopingense, a new species of Orchidaceae from Yunnan, China, Phytotaxa 521 (4), pp. 244-248 : 245

Cleisostoma luopingense Q. Liu & X.F Wu , sp. nov. ( Figure 1 )

Type:— China. Yunnan: Luoping County, Wanfengshan Nature Reserve , epiphyte on tree trunks of limestone forest, 1560-1600 m, 7 May 2020, Q . Liu 748 (holotype: HFTC!)

Diagnosis: — Cleisostoma luopingense is different from the C. williamsonii in having unbranched inflorescence and laxly arranged 6–10 flowers, elliptic petals (size: 3.0–3.2 × 1.8–2.0 mm), back wall callus of spur yellow, T-shaped and mid-lobule deeply bilobed at base, and column without stelidia.

Epiphytic herb, plants often pendulous. Stems to 40–50 cm, slender, ca. 2 mm in diameter, often branched, many leaved, internodes 1.0– 1.8 cm. Leaves straight or slightly arching, terete, usually 4.7–9.5 cm × 1.5–2.0 mm, sometimes densely covered with purple spots, acute. Inflorescence lateral, 4.0– 5.2 cm in length, unbranched, 6-10–flowered, flowers laxly arranged; floral bracts ovate, ca. 1.2 × 1.6 mm. Flowers opening widely, pink, and lateral lobes of lip deep yellow; pedicel and ovary ca. 5 mm, slender. Dorsal sepal ovate-elliptic, concave, 2.8–3.0×2.0– 2.1 mm, rounded; lateral sepals obliquely ovate-elliptic, 3.5–3.8 × 2.0– 2.2 mm, base adnate to column foot, obtuse. Petals elliptic, 3.0– 3.2 × 1.8–2.0 mm, rounded. Lip with lateral lobes erect, deltoid, ca. 2.0 × 1.2 mm, incurved, inner side with densely papillae; mid-lobe sagittate-triangular, ca. 3.0 × 2.0 mm, fleshy; spur globose, ca. 1.0 mm in diameter, concave, interior conspicuously septate, with a back wall callus; callus 3-lobed, yellow, T-shaped; lateral lobules nearly hornshaped; mid-lobule deeply bilobed at base and densely papillate. Column stout, ca. 2.0 mm, without stelidia; anther cap subglobose, ca. 1.0 mm in diameter; stipe short, broadly ovate-triangular; viscidium nearly crescent-shaped.

Etymology:—The specific epithet refers to the locality of Luoping county where this new species has been found.

Distribution and habitat:—At present, the new species is only known from Wanfengshan Nature Reserve, Luoping County, Yunnan Province, China. It was found growing as epiphytes on tree trunks in limestone forest, dominated by Cyclobalanopsis glaucoides Schottky (Fagaceae) , Lithocarpus glaber (Thunberg) Nakai (Fagaceae) , Platycarya strobilacea Siebold & Zuccarini (Juglandaceae) , Fraxinus chinensis Roxburgh (Oleaceae) , as well as some of other orchid species, including Bulbophyllum andersonii (J. D. Hooker) J. J. Smith , Eria coronaria (Lindley) H. G. Reichenbach , Luisia brachystachys (Lindley) Blume , Liparis distans C. B. Clarke , Conchidium rhomboidale (Tang & F. T. Wang) S. C. Chen & J. J. Wood.

Phenology:—Flowering from April to May.

Note:—Morphologically, Cleisostoma luopingense is similar to C. williamsonii (H. G. Reichenbach) Garay (1972: 176) in their vegetative as well as floral morphology. However, the new species can be differentiated from the latter by having unbranched inflorescence and laxly arranged 6-10 flowers, elliptic petals (size: 3.0- 3.2 × 1.8-2.0 mm), back wall callus of spur yellow, T-shaped and mid-lobule deeply bilobed at base, column without stelidia (vs: branched inflorescence and densely many flowered, oblong petals, (size: 2.2 × 1.0 mm), back wall callus of spur white, T-shaped and mid-lobule shallowly bilobed at base, column with conspicuously dentate stelidia in C. williamsonii ) ( Seidenfaden 1975; Chen & Wood, 2009). More detailed information of distinction between two species seen as Table 1.

Having said that, it is well understood that the new species C. luopingense (section Complicatum ) and C. williamsonii (section Mitriformes ) belong to two different sections of Cleisostoma . This calls for a thorough investigation of the sectional delimitation of the genus, however, this cannot be possible without a phylogenetic assessment with full representation of the members of this genus.

Figures

FIGURE 1. Cleisostoma luopingense Q. Liu & X.F Wu, sp. nov.A. Habitat (Wanfengshan Nature Reserve); B & C. Plant in the field; D. Inflorescence; E & F & G. Front, lateral and back view of flower; H. Floral bract; I. Sepals and petals; J & K. Lateral and front view of column and lip; L. Back callus of spur; M. Pollinarium; N. Anther cap; O. Longitudinal and transverse section of spur. (Photographed by Q. Liu)