Schizostachyum dakrongense N.H.Xia, Z.Y.Cai, Y.H.Tong & T.C.Vu, 2020

Cai, Zhuo-Yu, Tong, Yi-Hua, Vu, Tien-Chinh, Ni, Jing-Bo & Xia, Nian-He, 2020, Schizostachyum dakrongense (Poaceae, Bambusoideae), a new species from Dakrong Nature Reserve, Vietnam, PhytoKeys 138, pp. 179-186 : 179

Schizostachyum dakrongense N.H.Xia, Z.Y.Cai, Y.H.Tong & T.C.Vu sp. nov. Figures 1 , 2

Type.

Vietnam. Quang Tri Province: Dakrong Nature Reserve, 16°37'16.80"N, 106°52'1.80"E, alt. ca. 200m, 15 Nov. 2018, N.H. Xia et al BVN20181114 (holotype: IBSC!; isotype: VNMN!).

Diagnosis.

This new species resembles Schizostachyum hainanense in having culm sheaths with an asymmetrically concave apex and well-developed oral setae. However, S. dakrongense differs from S. hainanense in its pseudospikelets having a terminal rachilla segment with ciliate margin, and 6 bracts; the base of the culm sheath outer margin with a slight projection below its point of attachment; culm sheath blades that are usually less than half as long as the sheath proper; pale-puberulent and sparsely pilosulous leaf blade abaxial surfaces.

Description.

Culms erect, apex pendulous, 6-8 m tall, ca. 1.5 cm in diameter; internodes ca. 40 cm long, slightly siliceous and scabrous, with sparse white hairs, sometimes with white waxy powder, with an especially conspicuous white-powdery and brown-yellow setaceous zone ca. 1 cm wide just below each node; walls 1-2 mm thick. Culm sheaths up to 23 cm long, dark brown, covered with white powder and appressed brown hairs, margins sparsely ciliate, apex asymmetric, concave (ca. 9 mm deep), base of outer margin with a slight projection below point of attachment; auricles absent; oral setae well-developed, up to 20 mm or longer; ligule up to ca. 1 mm long, fringes of margin ca. 10 mm long; culm sheath blade narrowly lanceolate, reflexed, entire, usually less than half as long as culm sheath, adaxial side covered with dense white and brown hairs, especially at the base. Branches numerous and subequal, 30-50 cm long. Foliage leaves complements with 6-10 leaves; leaf blades oblong-lanceolate or linear-lanceolate, 10-21 cm long, 1.3-3.7 cm wide, adaxial surface slightly scabrous, abaxial surface pale-puberulent and sparsely pilosulous; sheaths 3-8 cm long, glabrous; auricles absent; oral setae well developed, pale, 10-15 mm long; ligule up to ca. 0.5 mm long, margin fimbriate. Pseudospikelets with 1 floret, clustered on leafy flowering branches, fusiform, ca. 20 mm long; prophylls ca. 2.5 mm long, ovate-lanceolate or triangular, apex acute or emarginate, abaxial surface glabrous or hairy; bracts (5-)6, ovate or ovate-lanceolate, apex emarginate, obtuse to acute or mucronate, abaxial surface glabrous or hairy, margin ciliate or not, the lowest bract without buds in its axils, the top two each with a bud in their axils, the middle ones with a bud in their axil or not; glumes absent; rachilla ca. 1 mm long, terminal segment enlarged, disciform, margin ciliate; lemma ca. 12 mm long, ovate-lanceolate, involute, apex acuminate mucronate, many-veined, margins ciliate or not; palea ca. 15 mm, strongly involute, upper portion indurate, lower portion soft, apex mucronate; lodicules absent; filaments white, ca. 13 mm long, free, anthers ca. 6 mm long, brownish yellow; ovary ovoid, glabrous, style ca. 15 mm long, stigmas 3, purple, ca. 1.5 mm long, plumose. Fruit unknown.

Etymology.

The species epithet “dakrongense” refers to the type locality: Dakrong Nature Reserve, Quang Tri Province, Vietnam.

Phenology.

New shoots are found from summer to autumn.

Distribution and habit.

According to our investigations and the available data, S. dakrongense is only distributed in Dakrong Nature Reserve. It commonly occurs in evergreen forest at an elevation of ca. 200 m, together with Eurycoma longifolia Jack, Ficus hirta var. roxburghii King, Archidendron occultatum (Gagnep.) I.C. Nielsen, and a species of Ochna .

Conservation status.

The species is found in a protected area, so its environment appears to be relatively stable. It is locally common. However, the area of distribution is less than 400 km2. According to International Union for Conservation of Nature (IUCN) Red List categories and criteria, this species should be treated as Endangered (EN) ( IUCN 2012).

Figures

Figure 1. Morphological character of S. dakrongense sp. nov. A Culm sheath B, C apex of culm sheath D branches E pseudospikelets and anthers F foliage blades G pseudospikelets and stigmas.

Figure 2. Morphological character of S. dakrongense sp. nov. and comparisons between S. dakrongense and S. hainanense. A Ovary and style B stigmas C prophylls D, G bracts E stamens F Palea (left) and Lemma (right) H 1 base of culm sheath outer margin of S. dakrongense H 2 base of culm sheath outer margin of S. hainanense I 1 rachilla of S. dakrongense with ciliate margin I 2 rachilla of S. hainanense with glabrous margin J 1 Leaf abaxial surface of S. dakrongense pale-puberulent and sparsely pilosulous J 2 leaf abaxial surface of S. hainanense glabrous. Scale bars: 1 cm (A, F, H 1, H 2); 1 mm (B-E, G, I 1, I 2, J 1, J 2).