Sonerila cornuta K.S.Nguyen, Aver. & C.W.Lin, 2025

Nguyen, Khang Sinh, Averyanov, Leonid V. & Lin, Che Wei, 2025, New species, Sonerila cornuta and S. phaluongensis (Melastomataceae), from northern Vietnam, Phytotaxa 696 (2), pp. 158-168 : 159-162

Sonerila cornuta K.S.Nguyen, Aver. & C.W.Lin , sp. nov. ( Figs. 1 & 2 )

Type: — VIETNAM. Nghe An Province: Ky Son District, Na Ngoi Municipality, eastern slopes of Phu Xai Lai Leng Mountain, primary very humid broad-leaved forest on steep mountain slopes composed of sandstone and gray shale at elevation of 2400–2700 m a.s.l., around point 19°12’17.7’’N 104°11’06.6’’E, lithophytic or terrestrial creeping herb, flowers purple, very common from 2,400 – 2,700 m a.s.l., 25 October 2013, L. Averyanov, N. T. Hiep, N. S. Khang, L. M. Tuan, N. A. Trang, L. H. Dan, CPC 6245 (holotype: LE LE 01253136 http://re.herbariumle.ru/01253136, photos LE LE 01124785 http://re.herbariumle.ru/01124785).

Diagnosis: — Sonerila cornuta resembles S. reptans J.Wai & J.M.Hu (2023: 131) with creeping to ascending, many branched stems, hairy leaves, and terminal scorpioid, few-flowered cymes. However, it is distinguished from S. reptans in ovate or broadly lanceolate leaves (vs. elliptic or elliptic-ovate) acute or acuminate at apex (vs. acute or obtuse), and 3 or 4 (vs. 2 or 3) pairs of secondary veins, obclavate hypanthium (vs. cylindrical-campanulate or obconical) covered by purple hispid, partially glandular hairs (vs. hairs white, simple, woolly), and purple subulate anthers (vs. yellow linear-lanceolate) with two prominent, S-curved basal lobes (vs. basal lobes rather straight, inconspicuous).

Etymology: —The species name refers two prominent, horn-shaped basal lobes of anther.

Description:— Lithophytic or terrestrial, perennial herbs. Stems creeping with suberect upper stem, many-branched, rooting at nodes when procumbent; stem terete, 8–14 cm tall, internodes 1–3.5 cm long, 1.5–2.5 mm thick, shorter on the distal branches, pale yellow, pale pinkish, pink, or light greenish, villous, hirsute or pilose. Leaves opposite, decussate, isomorphic or slightly dimorphic, subequal or unequal in sizes in each pair; petioles yellowishgreen, 0.7–2.8 cm long, densely pink to magenta, villous, hirsute or pilose; leaf blade chartaceous, symmetrical or sometimes slightly oblique, ovate or broadly lanceolate, 0.7–4.2 × 0.5–3 cm; adaxial surface bright green, densely white to pinkish hirsute, abaxial surface sparsely to densely white to pinkish hirsute; apex acute or attenuate, base cordate or rounded, margins denticulate with rows of magenta hairs; venation pinnate, primary vein shallowly grooved above, and prominent on the abaxial surface; secondary veins 3 or 4 pairs, arising from both sides of primary vein in an alternate or occasionally sub-opposite manner. Inflorescence terminal, simple scorpioid cyme, erect or ascending, 2–6-flowered; peduncles terete, 0.8–3.5 cm long, yellowish-pink, pale orange or light green, sparsely to densely hirsute with glandular hispid hairs; pedicels, ovary, hypanthium, sepals and petals pubescent with scattered to dense, purple, long, hispid, multicellular, simple and glandular (capitate) hairs to 1 mm long. Flowers 3-merous; pedicels 1.5–2 mm long, yellowish-pink. Hypanthium obclavate, pink to yellowish, 5–6 mm long, 2.2–3 mm in diameter. Sepals 3, broadly triangular, 1–1.5 × ca. 1.5 mm. Petals 3, pink-purple, oblong to obovate-oblong, slightly oblique, 13–15 × 4–5 mm. Stamens 3, isomorphic, entirely purplish-pink and glabrous; filaments slightly flattened, 7–10 mm long; anther narrowly cylindric, incurved, subulate and falcate, 8–10 mm long, with two pores at apex; anther base forked into 2 finger-like, S-curved lobes, 2–2.5 mm long. Ovary ca. 3–4 mm long, 3-locular; ovary crown shortly cylindrical, 3-winged, ca. 1 mm high; ovules numerous. Style filiform, purple, 15–17 mm long; stigma obscurely capitate. Fruit cupuliform capsule, 6–7 × 3.5–4.5 mm.

Distribution: — Vietnam, Nghe An Province (Ky Son District). Probably stenoendemic to Phu Xai Lai Leng Mountains.

Ecology and phenology: —Lithophytic and terrestrial creeping herb. Primary humid broad-leaved evergreen highland tropical forest on sandstone and shale at elevations of 2100–2700 m a.s.l. Occasional. Flowers in September– October.

Proposed IUCN conservation status: —This species is presently known from two close locations distant for ca. 10 km from each other in the highlands of the Phu Xai Lai Leng Mountains. The current population status of the new species is unknown after the accomplishment of road network construction in the past. Therefore, its conservation status should be considered as Data Deficient (DD).

Note: —Among the known Sonerila species in Vietnam, S. cornuta bears morphological resemblances to S. cantonensis Stapf (1892: 302) . Both species share characteristics such as shorter plants, hairy stems and inflorescence, and ovate leaves. However, S. cornuta is distinct from the latter due to its lamina densely hirsute above (vs. sparsely appressed setose or strigose) with a cordate or rounded base (vs. cuneate to obtuse), and the anthers uniformly purple (vs. yellow) with two S-curved base lobes (vs. base deeply cordate). A detailed comparison of S. cornuta and two other morphologically similar species, S. reptans and S. cantonensis are presented in Table 1.

Additionally studied specimen (paratype): — VIETNAM, Nghe An Province, Ky Son District, Na Ngoi Municipality, north-eastern slopes of Phu Xai Lai Leng mountain system, primary very humid broad-leaved forest with Cunninghamia konishii Hayata as emergent on steep mountain slopes composed of gray shale at elevation 2100–2700 m a.s.l. around point 19°13’52.9’’N 104°05’30.5’’E, terrestrial creeping herb on very steep shady humid slope of northern exposition, flowers purple, locally common, 25 October 2013, L.Averyanov, N.T.Hiep, N.S.Khang, L.M.Tuan, N.A.Trang, L.H.Dan, CPC 6261 (LE LE01253092 http://re.herbariumle.ru/01253092).

Figures

FIGURE 1. Sonerila cornuta A. Flowering plant; B, B'. Portions of leaf, adaxial and abaxial surfaces; C, C'. Flower, frontal and side views; D, D'. Stamens, frontal and half-side views; E. Hypanthium, side view; F. Fruit, side view. Drawing by Che Wei Lin from the type specimen, L. Averyanov, N.T. Hiep, N.S. Khang, L.M. Tuan, N.A. Trang, L.H. Dan, CPC 6245.

FIGURE 2. Sonerila cornuta A, B. Flowering plants in natural habitat; C. Inflorescence; D, E. Flower, frontal and side views.All photos by Khang Sinh Nguyen of plants used for the preparation of the type herbarium specimen, L. Averyanov, N.T. Hiep, N.S. Khang, L.M. Tuan, N.A. Trang, L.H. Dan, CPC 6245.