Dendrobium niveolabium Handoyo, Naive, Ormerod & J.Champ., 2021

Naive, Mark Arcebal K., Handoyo, Frankie, Ormerod, Paul & Champion, Jeffrey, 2021, Dendrobium niveolabium (Orchidaceae, section Grastidium), a new Dendrobiinae species from Papua, Indonesia, Phytotaxa 490 (3), pp. 271-277 : 272

Dendrobium niveolabium Handoyo, Naive, Ormerod & J.Champ. , sp. nov ( Fig. 1–2 )

This species is similar to Dendrobium papyraceum J.J.Sm. (1913: 113) but differs significantly in having narrowly oblong to lanceolate leaves, oblong to obovate petals, strongly recurved, plain white labellum with white, entire basal keel and larger midlobe ( Fig. 3 ). Type:— INDONESIA. West Papua, Sorong Regency , cultivated plant, August 2020, JKC 22 (holotype THBB) .

Epiphytic herbaceous plant. Roots 3–4 mm wide, smooth, flattened. Stems clustered, erect to ascending, up to 50 cm long, 3–4 mm in diameter, terete; internodes 1.4–2.0 cm long, covered with persistent sheaths; sheaths green, glabrous when young, brown, striate, puberulous when old. Leaves distichous, 6–7 cm long by 1.5 cm wide, narrowly oblong to lanceolate, subcoriaceous, green adaxially, pale green abaxially, glabrous on both sides, margin entire, apex obtuse, unequally bilobed. Inflorescence emerging from leaf-sheaths between the nodes, 2 (very rarely 3) flowered; peduncle erect to suberect, 4–6 mm long, flattened, white; floral bract triangular, 1–2 mm long, white, apex acute. Pedicel and ovary clavate, 13–15 mm long, sulcate, glabrous, light green to yellowish green. Flowers opening widely, up to 22 mm across, ephemeral, lasts 2–3 days. Dorsal sepal erect to reflexed, 11.5–12 mm long by 5.5–5.7 mm wide, oblongelliptic, fleshy, brownish yellow to greenish yellow, glabrous, margin entire, apex acute. Lateral sepals spreading to reflexed, 10–15 mm long by 6.5–8.0 mm wide near the base, obliquely triangular-ovate to slightly falcate, base fused together for 4 mm forming a mentum, apex obtuse to subacute; mentum broadly conical, obtuse, slightly incurved, 5–7 mm long by 5–6 mm in diam. Petals spreading to reflexed, 10–13 mm long by 4–5 mm wide, oblong to obovate, subfalcate, fleshy, brownish yellow to greenish yellow, glabrous, margin entire, apex obtuse to subacute. Lip 3-lobed, strongly recurved, 13 mm long, 8–9 mm wide when flattened, with a basal keel extending to the base of the midlobe, entire; sidelobes erect to suberect, 6–7 mm long, 1.8–2 mm wide, obliquely oblong to somewhat triangular, margins irregularly crenulate, rugulose, apex obliquely acute, slightly serrate; midlobe 6–7 mm long, 8–9 mm wide when flattened, obovate to obcordate, decurved, rugulose adaxially, centre thickened, margin slightly revolute, apex broadly apiculate. Column porrect, stout, 4–4.5 mm long, c. 2.7 mm in diam. at base, white, glabrous; column foot conspicuous, c. 5 mm long, incurved, white with burgundy streaks, tip yellowish; stelidia short, 2–3 mm long, broadly ensiform, apex praemorse; pollinia 2, each pair can be divided into two parts, c. 1.2 mm long, narrowly ovoid, yellowish; anther cap c. 1.7 mm long by 1.4 mm across, oblong, cucullate. Capsule not seen.

Distribution:— The species is currently only known in Sorong Regency, West Papua Province, Indonesia.

Ecology:— Found growing as an epiphyte in lowland tropical forests. In cultivation, the species thrive at an elevation of 1,100 m a.s.l. with brightly lit environment.

Phenology:— Observed flowering in cultivation in March, May and November.

Etymology:— The specific epithet ‘ niveolabium ’ was coined from the Latin word niveo which means white and labium meaning lip in reference to its pure white labellum.

Provisional conservation status:— Owing to the insufficient information on its distribution and population size in the wild, we herein treat Dendrobium niveolabium as ‘Data Deficient’ (DD) following the Red List criteria of the IUCN Standard and Petitions Subcommittee (2019). Further investigation and assessment should be done to determine whether there are known populations in other areas, information on population size and trends and threats to the species in New Guinea.

Taxonomic Notes:— Based on overall morphology, Dendrobium niveolabium appears to be closely similar to D. papyraceum . However, D. niveolabium differs significantly in having narrowly oblong to lanceolate (vs. lanceolate in D. papyraceum ) leaves, oblong (vs. elliptic in D. papyraceum ) petals, strongly recurved, plain white (vs. slightly recurved, pale yellow, lateral lobes white, at apex violet, inside with short transverse violet stripes, midlobe white in the centre, with narrow violet margins in D. papyraceum ) labellum with white, entire (vs. pale orange, crispate in D. payraceum ) basal keel, and 6–7 mm long by 8–9 mm wide (vs. 4 mm long by 5.7 mm wide) midlobe. The species also resembles D. hollandianum J.J.Sm. (1913: 112) , D. igneum J.J.Sm. (1908: 17) , D. ocranthum Schltr. (1905: 171) and D. patentissimum J.J.Sm. (1913: 112) . A key to Dendrobium niveolabium and its morphologically allied species is presented below.

Figures

FIGURE 1. Dendrobium niveolabium Handoyo, Naive, Ormerod & J.Champ.A. Habit B. Leaves C. Flower D. Dorsal sepal, petal, lateral sepal E. Column F. Labellum G. Profile view of column, column foot, labellum. Drawn by: Feby Nazuar.

FIGURE 2. Dendrobium niveolabium Handoyo, Naive, Ormerod & J.Champ. A. Flower with spreading floral segments B. Flowers with reflexed floral segments C. Dorsal sepal D. Petals E. Lateral sepals F. Labellum G. Profile view of column, column foot and labellum H. Detail of column and column foot I. Ventral view of column and column foot. Photos by: J.K. Champion.

FIGURE 3. Comparison between D. papyraceum (A–D) and D. niveolabium (E–H). A. Flower (scale bar: 10 mm) B. Details of labellum (scale bar: 10 mm) C. Column and column foot D. Pedicel, ovary, column, mentum (scale bar: 10 mm) E. Flower (scale bar: 10 mm) F. Details of Labellum (scale bar: 10 mm) G. Column and column foot H. Pedicel, ovary, column, mentum (scale bar: 5 mm). Photos by: J.K. Champion.