Dendrobium (section Brevisaccata Kraenzl.) taeniocaule Schuit., Juswara & Droissart, 2016

Juswara, Lina, Schuiteman, Andre & Droissart, Vincent, 2016, Four new orchid species from the Lengguru fold belt, West Papua, Indonesia, PhytoKeys 61, pp. 47-59 : 51

Dendrobium (section Brevisaccata Kraenzl.) taeniocaule Schuit., Juswara & Droissart sp. nov. Figs 2C , 4A-E

Diagnosis.

Similar to Dendrobium viridiflorum F.M.Bailey in the flattened stems and the sympodially branching inflorescences with 1-flowered branches. The new species differs from Dendrobium viridiflorum in the relatively much shorter mentum (3.6 mm versus 7 mm long, with the free part of the lip being of about equal length in the two species), the relatively much broader dorsal sepal, in the lip being wider than long (versus longer than wide), and especially in the much wider (8.5 versus 3.2 mm), bilobulate (versus entire) mid-lobe of the lip.

Type.

Indonesia, West Papua Province, Kaimana Regency, Lobo village, Triton Bay, 03°43.7962'S, 134°3.5962'E, 28/10/2014, Droissart & Juswara 1739 (holotype: BO!, spirit material).

Description.

Epiphytic herb. Rhizome short, creeping; roots 1 mm diam., minutely verrucose. Pseudobulbs erect, yellowish green, elongate, bilaterally flattened, 16-21 × 0.4-0.5 cm; internodes 2.3-2.6 cm long, each internode narrowed towards the base; leafy throughout, except for two or three basal internodes; 6-8-leaved. Leaves deep green, long-lived, patent, oblong, 2.0-3.3 × 0.6-0.9 cm; apex unequally bilobed; sheath much shorter than the internode. Inflorescence arising from the apex of the internodes in the upper part of the stem, sympodially branching with age, with up to 3 branches, each branch 3-8 mm long, 1-flowered; peduncle c. 6 mm long, covered with scales in the basal part. Floral bract triangular, closely appressed, 2.9 mm long, apex apiculate. Pedicel 2.6 mm long ovary at right angles to the pedicel, 2.6 mm long, glabrous; at the base of the pedicel with an abortive rachis. Flower 10.3 mm high, glabrous; sepals greenish white, tinged pale purple abaxially and on the mentum; petals pale green; lip white; column pale green suffused with purple; anther pale green. Dorsal sepal broadly ovate, 4.1 × 3.3 mm, 5-nerved, obtuse. Lateral sepals obliquely broadly ovate, the free part 5.3 × 4.3 mm, 5-nerved, obtuse; mentum cylindrical, 3.6 mm long, apex rounded, the closed apical part 2.8 mm long. Petals linear-oblong, 4.4 × 1.2 mm, acuminate, 3-nerved, margin in upper third finely papillose. Lip 3-lobed, clawed, when flattened 6.7 × 8.5 mm excluding the c. 4 mm long, linear claw; lateral lobes subfalcate-oblong, patent, 2.7 × 1.0 mm; mid-lobe clawed, bilobulate (the whole lip appearing 4-lobulate), 5.7 × 8.5 mm; mid-lobe claw obtrapeziform, 1.7 × 4.4. mm; lobules of the mid-lobe rectangular-orbicular, 3.3 × 4.2 mm; the whole of the lip, except for the lateral lobes and the lobules of the mid-lobe, occupied by a sharply delimited swelling, which has two broad longitudinal crests with a narrow rib in between and which projects backwards over the claw of the lip for 0.3 mm. Column broadly conical in front view, 1.7 mm long, wings very short, truncate; foot 3.6 mm long; stigma large, 1.6 mm wide, rostellum a simple transverse ridge; anther cucullate-rectangular, 1.1 mm wide, glabrous; pollinia not seen.

Distribution and habitat.

Dendrobium taeniocaule is only known from the Lengguru fold belt in West Papua. It is currently recorded from a single locality in the Triton Bay area, near the village of Lobo (Fig. 1 ). The only population seen so far was found in submontane forest at 1114 m elevation, the plants growing epiphytically on a vertical, lichen-covered trunk of a tree.

Etymology.

From the Greek taenia, a band or strap, and caulon, stem; referring to the flattened, band-shaped pseudobulbs.

Notes.

This species has only one obvious close relative, which is the widespread Dendrobium viridiflorum . Uniquely in section Brevisaccata , these two species share flattened stems and abbreviated inflorescences that produce up to 3, 1-flowered branches in succession over a longer period. The other species in the section have terete stems and flowers produced simultaneously on elongate racemes. In addition to clear morphological differences, as indicated in the diagnosis, the two first-mentioned species also have different ecologies. While Dendrobium viridiflorum is exclusively found in mangroves and coastal forest below 200 m, Dendrobium taeniocaule occurs in submontane forest above 1000 m.

Figures

Figure 1. Main localities sampled during Lengguru 2014 expedition and distribution of the four new species in West Papua, Indonesia.

Figure 2. A Bulbophyllum leucoglossum: 1 flower 2 dorsal sepal 3 lateral sepal 4 petal; 5, lip, adaxial view 6 lip, abaxial view 7 detail of crest on lip 8 column and base of lip; all after Droissart & Juswara 1789; B Dendrobium centrosepalum: 1 flower 2 flower, lateral view 3 floral bract 4 dorsal sepal 5 lateral sepal 6 petal 7 lip 8 flower, cut open 9 column 10 anther 11 pollinia; all after Droissart & Juswara 1736; C Dendrobium taeniocaule: 1 flower 2 dorsal sepal 3 lateral sepal 4 petal 5 lip 6 mentum 7 column, lateral view 8 column, ventral view; all after Droissart & Juswara 1739; D Taeniophyllum pyriforme: 1 flower 2 dorsal sepal 3 lateral sepal 4 petal 5 lip 6 column 7 anther, dorsal view 8 anther, lateral view; all after Droissart & Juswara 1735. Single scale bar = 1 mm; double scale bar = 1 cm. Drawing: Judi Stone.

Figure 4. Photographs of living type specimens and habitats. Dendrobium taeniocaule: A habitat and habit B plant C flower and part of pseudobulb D flower, front view E flower, side view. Taeniophyllum pyriforme: F habitat and habit G plant and inflorescence H inflorescence and flowers close-up. Photos: Vincent Droissart.