Corybas papillatus Inuthai, Chantanaorr. & Suddee, 2021

Inuthai, Janejaree, Chantanaorrapint, Sahut, Poopath, Manop, Tetsana, Naiyana, Kiewbang, Wittawat & Suddee, Somran, 2021, Corybas papillatus (Orchidaceae), a new orchid species from peninsular Thailand, PhytoKeys 183, pp. 1-7 : 1

Corybas papillatus Inuthai, Chantanaorr. & Suddee sp. nov.

Figs 1 , 2

Diagnosis.

Similar to Corybas villosus J. Dransf. & Gord. Sm., but differs in the absence of dorsal sepal keel and the lateral sepals adnate laterally at the base to the connate petals.

Type.

Thailand. Nakhon Si Thammarat province, Khao Luang National Park, near summit of Khao Luang Mt. , 08°29'36.8"N, 099°43'38.9"E, ca. 1,700 m alt., 4 July 2018, M. Poopath, N. Tetsana, W. Kiewbang, C. Hemrat & S. Jirakorn 2201 (holotype BKF!, spirit material) .

Small terrestrial herb with underground tubers. Tubers globose or ovoid, fleshy, 3-4 mm diam. Stem erect, whitish-green, 5-12 mm long, 1-1.5 mm diam., with a basal sheath; stolon whitish, hairy, up to 2 cm long, 1-1.2 mm diam. Foliage leaf sessile, cordate, long acuminate at apex, glabrous, 6-10 mm long, 6-8 mm wide at the widest point, flat, only slightly undulate along margin, pale green with paler veins, the veins scarcely conspicuous. Inflorescence one-flowered, terminal; bract pale green, lanceolate-triangular, long acuminate, 5-6 mm long, recurved. Flower dark purple. Dorsal sepal purplish, erect below, then strongly curved above, hooded and clasping labellum throughout its length, spathulate, ca. 15 mm long, 8-10 mm wide, rounded at apex, apical margins denticulate, abaxial (dorsal) surface bearing irregular papillae in the upper half. Lateral sepals greenish-white, linear-triangular to antenna-like, ca. 25 mm long, laterally adnate to the petals in the basal ca. 1 mm. Petals greenish-white, connate at the base for ca. 1 mm, free above, similar to lateral sepals but shorter, ca. 22 mm long. Labellum differentiated into 2 parts, erect in basal half and strongly reflexed above, ca. 17 mm long in total length; the basal half with margins strongly inrolled throughout, and forming a tube with the dorsal sepal, ca. 7 mm long; the upper half reflexed and expanded, orbicular, ca. 10 mm diam., margin erose, reddish-purple excepted for a white zone just below the margins; mouth of throat very deeply V-shaped; adaxial surface bearing short hairs; spurs 2, divergent, conical, ca. 3 mm long. Column very short, ca. 1.5 mm long; stigma rounded, ca. 0.5 mm diam.; anther erect, smooth; pollinia not seen. Ovary green, glabrous, ca. 2 mm long. Capsule (immature) erect, ellipsoid or fusiform, 5-7 mm long, 2.5-3 mm diam. Seed not seen.

Phenology.

Flowering and fruiting observed in July.

Habitat and ecology.

The new species was found growing amongst bryophytes (Fig. 1A-C ), such as Acroporium sp., Bazzania sp., and Schistochila aligera (Nees & Blume) J.B. Jack & Steph., on humus in shade in montane forest, ca. 1,700 m above sea level.

Distribution.

Corybas papillatus is only known from the type locality (Fig. 3 ), however, it may also occur in other areas in peninsular Thailand with similar vegetation type.

Etymology.

The specific epithet ' Corybas papillatus ' alludes to occurrence of irregular papillae in upper portion of abaxial (dorsal) surface of dorsal sepal.

Conservation status.

We consider it likely that if a formal assessment were performed, this species would be categorized as Critically Endangered (CR (D)) based on a preliminary risk of extinction assessment using the IUCN red list categories and criteria ( IUCN 2019). This species is known from only four individuals from the type locality which attracts high numbers of camping tourists. Although we returned to the same locality and tried to find more specimens in 2020 it could not be found again. The species is, however, easily be overlooked in the field because of its small size.

Figures

Figure 1. Corybas papillatus Inuthai, Chantanaorr. & Suddee A, B plants in natural habitat, on humus associated with Bazzania sp. and Acroporium sp. C plant with immature fruit D, E flowers D front view E lateral view F immature flower G underground parts with tubers. Photographs by W. Kiewbang.

Figure 2. Corybas papillatus Inuthai, Chantanaorr. & Suddee A whole plant with flower and tubers B plant with immature flower C mature flower, lateral view D plant with immature fruit E floral bract, F, G dorsal sepal F ventral view G lateral view H lateral sepals and petals I labellum J, K column, J lateral view, K front view. Drawn by J. Inuthai.

Figure 3. Type locality of Corybas papillatus Inuthai, Chantanaorr. & Suddee (•).