Dendrobium yongjiaense Z.Zhou & S.R.Lan, 2020

Zhou, Zhuang, Zhang, Sai, Yang, Yan-Ping, Ma, Liang & Lan, Si-Ren, 2020, Morphological and molecular evidence for a new species from China: Dendrobium yongjiaense (Orchidaceae: Malaxideae), Phytotaxa 441 (2), pp. 203-210 : 209

Dendrobium yongjiaense Z.Zhou & S.R.Lan , sp. nov. (永⁂石斛; Figs. 2 , 3 )

Type:— China, Yongjia (永⁂), Zhejiang (ffiữ): lithophytic on rocks in mountain valleys, altitude 820–850 m, 12 October 2017, cultivated and flowered in Yongjia, 6 December 2019, Zhou 2019120601 (holotype: FAFC).

Diagnosis:—This new species is similar to D. monticola and D. strongylanthum , but it differs by its length of inflorescences (3.0–9.0 cm vs. 2.5–5 cm vs. ca. 13 cm), lip size (8.0–8.5 × 4.5–5.5 mm vs. 5.5–6.5 × 3.5–4.5 mm vs. ca. 8 × 4 mm), and a mid-lobe of the lip with densly distinct crystalline papillae and wrinkled 3–5 crest lines in middle (vs. slightly crispate).

Epiphytic herb; pseudobulbs erect, cylindric or narrowly fusiform, base slightly contracted, green or yellowish-green, previous year’s stems yellowish-green, 2.5–10.0 cm tall, with sheath 3–6 mm in diameter, with 3–9 nodes, current ones enclosed in leaf sheaths, leaf sheaths membranous, glabrous on both surfaces, light brown, mature old pseudobulbs naked, with yellowish white longitudinal lines. Leaves 3–9, leaf blade distichous, alternate on entire stem, ovate or oblong, 2–4 × 0.6–1.2 cm, base dilated into gibbous sheaths, apex unequally and shortly bilobed, each lobe acute, base expanded into sheaths, sheaths sparsely clasping when dry, sheath mouth obliquely truncate, the lowermost smaller than the uppermost, green or dull green above, pale green beneath, mid-vein grooved above and ribbed below. Inflorescences with 1–3 subterminal or lateral on upper part of stem and axillary racemes, suberect or nodding, 3.0–9.0 cm, usually taller than leaves, 6–15 flowered; rachis slender and glabrous; floral bracts ovate-lanceolate to triangular lanceolate, 3–5 mm long, apex acuminate, margin entire, 1-veined and distinctly keeled below, glabrous on both surfaces, yellowish green. Pedicel and ovary 5.0–8.0 mm long. Flowers whitish green or pale yellowish green, lightly fragrant. Dorsal sepal whitish green or pale yellowish green, narrowly ovate-lanceolate, 10.0–12.0 × 1.5–1.8 mm, 1–3- veined, hardly visible, long acuminate. Lateral sepals whitish green or pale yellowish green with purplish red stripes and spots at abaxial base, falcate-lanceolate, 9.5–10.0 × 3.5–4.0 mm at middle, 3–5-veined, apex acute, base oblique, abruptly contracted above middle. Petals whitish green or pale yellowish green with sparsely purplish red spots at abaxial base, narrowly ovate-lanceolate, slightly smaller than dorsal sepal, 9.5–11.5 × 1.2–1.5 mm, 1–3-veined, hardly visible, middle to apex slightly oblique. Lip pale yellowish green with dull purplish red stripes and spots at lateral lobes, 8.0–8.5 × 4.5–5.5 mm, shortly clawed, 3-lobed above middle, lateral lobes ovate-triangular, margin with comb-shaped teeth, apex sharply toothed; mid-lobe ovate-triangular, with dense and distinct crystalline papillae, distinctly crispate from margin to middle, wrinkled 3–5 crest lines in middle, apex acute; disk with 3 lamellate ridged projections, ridges thickly fleshy, terminating at base of mid-lobe, apex enlarged to triangle with wrinkled margin. Mentum yellowish green with purplish red spots stripes at apex, broadly conic, 3.3–4.7 mm in diameter, margins entire, incurved distally. Column dull purplish red, subterete, ca. 3.0 mm long with a foot 4.5–5.0 mm long, foot margin densely with fine papillae; anther cap dull purplish red, subglobose tapered to apex, densely papillate, front margin lacerate; pollinia 4, in 2 pairs, yellow, each pollinium narrowly elliptic, ca. 0.7 × 0.4 mm.

Phenology: —Flowering from November to December.

Etymology: —The species epithet refers to Yongjia County, where this new orchid was first found.

Distribution and habitat: — Dendrobium yongjiaense is so far only known within Yongjia, Zhejiang, China. It is lithophytic on sheer rocks at elevations of 800–820 m in mountain valleys.

Conservation status: — Dendrobium yongjiaense is discovered only from the type locality with one population which adjacent to the village about 500 m. The population has only approximately 50 individuals, half of them have been collected by rock climbers. Due to the medical value and rarity of Dendrobium , the risk of remaining plants being damaged is potentially high. According to the World Conservation Union Red List Categories and Criteria version 3.1 ( IUCN, 2001), D. yongjiaense should be preliminarily evaluated as critically endangered (CR).

Figures

FIGURE 2. Dendrobium yongjiaense Z.Zhou & S.R.Lan. A. Plant. B. Flower, front view. C. Flower with lateral sepals removed, side view. D. Lip, front view. E. Petal. F. Dorsal sepal. G. Lateral sepal. H. Column, front view. I. Pollinarium. Drawn by Zhuang Zhou.

FIGURE 3. Dendrobium yongjiaense Z.Zhou & S.R.Lan. A. Flowering plant. B. Inflorescences. C. Anatomy of the flower. D. Lip, side view. E. Pollinarium. F. Flower, front view. G. Flower with lateral sepals removed, side view. H. Column, front view. I. Lip, front view (left) and basal view (right). J–K.Anther cap, different view.