Schizostachyum sumpurkudusense Ritonga 2025, sp. nov.

Schizostachyum sumpurkudusense Ritonga, sp. nov. (Figs. 1–3). Type:— INDONESIA. Sumatra: West Sumatra, Sijunjung, Sumpur Kudus District, Sumpur Kudus Village, 0°27’16.0”S 100°53’36.4”E, 521 m, 9 August 2024, Muhammad Azli Ritonga 115 (holotype BO!, isotype ANDA!). Diagnosis:— Schizostachyum sumpurkudusense is morphologically similar to S. hantu such as culm- and leaf- sheath auricles prominent with long bristles, but S. sumpurkudusense is distinguished from S. hantu by culm is green, up to 7 m high and relatively erect (vs. pale green, up to 20 m high, first erect then leaning with age with long drop tips on S. hantu); culm internodes are up to 57.5 cm long (vs. up to 100 cm long on S. hantu); culm diameter is up to 1.3 cm (vs. up to 2.5 cm on S. hantu); culm sheath ligules are entire and glabrous (vs. dentate with bristles on S. hantu); culm sheath blades are spreading (vs. erect when young, later deflexed on S. hantu); adaxially blades at the base are glabrous or sometimes with scattered light brown to white hairs (vs. dense long white hairs adaxially at the base on S. hantu); and leaf sheath ligules are glabrous (vs. with bristles on S. hantu). Tufted clump, sympodial. Shoots green, covered by light brown hairs and scattered white wax, margin of sheaths blackish purple, blades erect to spreading, junction between the base of the blades and the culm sheath proper purplishgreen. Culms green, 5‒7 m high, 1.2‒1.3 cm in diameter, internodes 37.4‒57.5 cm long, erect, wall 2–4 mm thin, near the culm nodes of young culms covered by pale appressed hairs and white wax. Branches consist of several slender, sub-equal branches. Culm sheath relatively persistent or tardily caducous, covered by long, light brown hairs particularly near the base, 20.6‒24.1 × 6.9‒24.1 cm, green with a purplish flush, especially in the upper part near the base of the blades when young, turning brown with age; auricles 2‒3 mm high, prominent, curved outward with acute tips (look like a sickle), dark purple when young, turning brown with age, bristles up to 7 mm long; ligules entire, up to 2 mm high, glabrous; blades 8.8‒11.3 × 1.3‒1.7 cm, spreading, narrowly triangular to lanceolate with a narrow base, green with purplish flush near the base when young, turning brown with age, glabrous or sometimes covered by scattered light brown to white hairs adaxially particularly at the base, glabrous abaxially. Leaf blades 29‒37.3 × 4.5‒6 cm, green, oblong-lanceolate, abaxial pubescent; auricles up to 2 mm high, prominent, curved outward with acute tips (look like a sickle), bristles 7‒9 mm long; ligules entire, up to 1 mm high, glabrous. Inflorescence 5.6‒10.1 cm long, terminating a leafy branches, bearing dense groups of pseudospikelets at the nodes of its axis; pseudospikelet 2.3‒3.4 cm long, cylindrical with pointed tips, slender, green or green with purple tinges near the tip when young, becoming brown with age, covered by light brown to white hairs; glume c. 1.4 × 0.6 cm with long acute tips, covered by light brown to white hairs on outer part; lemma c. 1.3 × 0.5 cm long with long acute tips; palea c. 1.2 × 0.4 cm long with acute tips; stamens 6; filament 6‒6.5 mm long; style 1.4‒3.1 cm long; stigma 3, feathery, purple. Fruits not available. Phenology:—This species flower from August to December, with new shoots emerging from July to December. Distribution:—This species is known to grow only in West Sumatra, specifically in Sumpur Kudus Village, Sumpur Kudus District, Sijunjung Regency (Fig. 4). Habitat:—This species grows on forest edges, roadsides, and cliff edges in open areas at an elevation of 521 meters above sea level (Fig. 5). Etymology:—The specific epithet of the newly described species is derived from its type locality, Sumpur Kudus Village, West Sumatra, Indonesia. Uses and vernacular name:—The culms of S. sumpurkudusense are commonly used as stakes to support chili or cucumber plants. The vernacular name of this species in the Minangkabau language is buluah mounti. Provisional conservation status assessment:— Schizostachyum sumpurkudusense is endemic to West Sumatra and is known to exist in only a single clump. The AOO for S. sumpurkudusense is 4 km ², which falls under the criteria for Critically Endangered (CR) according to the IUCN Red List criteria B. Meanwhile, the EOO is recorded as 0 km². The observed clump consists of no more than 90 mature culms. This species grows along roadsides and near cliffs, making it vulnerable to threats such as landslides. Additionally, future road expansion could lead to the loss of this bamboo clump. Its use in local agriculture poses another potential threat through overexploitation. However, these threats have not yet been precisely measured. Accordingly, based on the IUCN (2024) criteria, S. sumpurkudusense is provisionally categorized as Near Threatened (NT), as the specific threats to its existence remain unclear and further surveys are needed to confirm its presence in other locations. Notes:— Schizostachyum sumpurkudusense shares similarities with S. hantu and also S. latifolium Gamble (1896: 117). A comparison of the morphological characteristics among S. sumpurkudusense, S. hantu, and S. latifolium is presented in Table 1.