Calanthe rubra S.H.Oh, H.J.Suh

Oh, Sang-Hun, Suh, Hwa-Jung, Park, Chong-Wook, C. - W & C. - W, 2015, Two new species of Calanthe (Orchidaceae: Epidendroideae) from Korea, Phytotaxa 218 (1), pp. 69-76 : 75-76

2. Calanthe rubra S.H.Oh, H.J.Suh & C.-W.Park, sp. nov. ( Figs. 4 , 5 )

Type:— KOREA. Jeollanam-do: Sinan-gun, Heuksan-myeon, Gageodo Island, 420 m, 18 May 2013, Suh 5499 (holotype, KB!).

Diagnosis: This species is similar to C. insularis and C. striata , but differs in its smaller flowers with purplish red sepals and petals and white spur.

Plants herbaceous, terrestrial, 31–39 cm tall. Pseudobulbs ovate or conical, 1–2 cm long, 1–2 cm in diameter. Leaves 3 or 4, biennial, incompletely spreading and convolute at anthesis, base forming a pseudostem, fully developed blade obovate-elliptic, 32–35 cm long, 5–9 cm wide, contracted basally into a petiole-like stalk 9–10 cm long; blade entire, puberulent abaxially, glabrous adaxially, apex acute or acuminate. Inflorescences racemose, erect on a scape arising from leaf axil, 31–39 cm long, puberulent; rachis 13–24 cm long, loosely 5–14-flowered; floral bracts lanceolate, 6–7 mm long, yellow, persistent. Flowers purplish red; pedicel and ovary 1.3–1.9 cm long, densely puberulent, pedicel purplish red, ovary green with purplish red ridges. Sepals subequal, ovate, 1.6–2.1 cm long, 0.7–1.0 cm wide, apex acuminate, sparsely purberulent, 5-veined; dorsal sepal concave, cymbiform; lateral sepals slightly narrower than dorsal sepal. Petals narrowly elliptic, 1.4–1.7 cm long, 0.6–0.7 cm wide, base narrowed, apex acuminate; lip adnate to column wings, flabellate, purplish red, deeply trilobed; midlobe obovate, wing-like, spreading, 5.8–6.6 mm long, apex slightly lobed, mucronate in sinus; lateral lobes falcate-obovate, oblique, 5.4–5.7 mm long, apex truncated or rounded; disk with 3 yellow ridges and 2 rows of white short hairs at base; spur slightly arcuate, parallel to ovary and pedicel, 0.7–1.1 cm long, white, obtuse apically, puberulent. Column ca. 4 mm long, thick, pale yellow; rostellum bilobed; pollinia waxy, in 2 groups of 8, with short caudicles, attached to an elliptic viscidium. Fruit ovoid, nodding. Fl. May.

Additional specimens examined:— KOREA. Jeollanam-do: Sinan-gun, Heuksan-myeon, Gageodo Island, 420 m, 17 May 2014, Oh & Suh 5927, 5928, 5929 ( TUT!).

Distribution and habitat:— Calanthe rubra occurs in open areas on Gageodo Island, Korea, surrounded by large rocks in broadleaf evergreen forests dominated by Castanopsis cuspidata . Populations of C. rubra are small with less than 30 individuals, and they decrease rather rapidly because of habitat destruction and collection for horticulture.

Phenology:— Calanthe rubra flowers in May and fruits June to August.

Etymology:— The specific epithet of C. rubra refers to its purplish red flowers.

Discussion:— Calanthe rubra is similar to C. insularis and C. striata , but easily distinguished by its flower color and size. The flowers of C. insularis and C. striata are yellow, whereas those of C. rubra are purplish red ( Table 1; Fig. 3 ). The unopened flowers have a strong red color. The spur of C. insularis is pale to creamy yellow in color and that of C. striata is yellow, whereas the spur of C. rubra is white ( Fig. 3 ). The flowers of C. rubra are smaller than those of C. insularis and C. striata ( Table 1). Calanthe rubra is considered endangered ( IUCN 2014; EN B2a,b(iii)) because of its limited occurrence on Gageodo Island, Korea.

Figures

FIGURE 3. Comparison of Calanthe insularis (A and E) and C. rubra (B and F) with C. striata (C and G), and C. aristulifera (D and H). A–D. Front view of flower. E–H. Lateral view of flower. Scale bar = 1 cm.

FIGURE 4. Calanthe rubra (Sinan-gun, Korea). Part of a mature leaf is broken.A. Plant. B. Leaf. C. Flower, front view. D. Flower, lateral view. E. Lip. F. Sepals and petals. G. Pollinia. Scale bar: A, B = 4 cm; C–F = 1 cm; G = 1 mm. t

FIGURE 5. Photograph of Calanthe rubra from Sinan-gun, Korea.