Sporoxeia vietnamensis D.V.Hai, Z.L.Lin & S.Jin Zeng, 2022

Thuy, Nguyen Thu, Zeng, Sijin, Hai, Do Van, Hoan, Duong Thi, Lin, Zheli & Deng, Yunfei, 2022, Sporoxeia vietnamensis (Melastomataceae), a new species from northern Vietnam, Phytotaxa 558 (3), pp. 283-290 : 284-289

Sporoxeia vietnamensis D.V.Hai, Z.L.Lin & S.Jin Zeng , sp. nov. ( Figs. 1–4 )

Type: — VIETNAM. Lao Cai Province: Van Ban District, Nam Xe Commune , elev. 1018 m, 22°03’28.1”N, 103°57’32.3”E, 31 July 2018, Do Van Hai, Hoang Van Chien DVH 99 (holotype HN!; isotypes HN!, IBSC!) .

Diagnosis: —The new species resembles S. blastifolia in having obtusely quadrangular stems, slightly unequal leaf blades with cuneate bases, and two secondary veins on each side of midvein, but differs by the leaf blades stiffly papery (vs. papery), larger (ca. 10 mm long vs. 3 mm long) and densely horned (vs. sparsely verrucose) hypanthia, larger (3–4 × 1.5–2 mm vs. almost invisible) calyx lobes, and larger (14–16 × 9–11 mm vs. ca. 4 × 4 mm) petals.

Description: —Shrubs to 1.5–2.5 m tall, bark smooth, grayish brown; young branchlets green, densely puberulent, obtusely quadrangular, old branchlets turning to brown, sparsely puberulent and lenticellate. Leaves opposite; petiole ferruginous to rufous, terete, 2.5–6 cm long, puberulent when young, then glabrescent; blade oblong to ovate-oblong, or broadly ovate, 9.5–19 × 4.5–10 cm, stiffly papery, base obtuse, broadly cuneate, margin inconspicuously denticulate, apex acuminate with a tip up to ca. 1 cm, adaxially light green, often with prominent whitish spots arranged in two lines on both sides of the midvein when young, abaxially green, ferruginous to rufous along midvein; secondary veins 2 on each side of midvein; tertiary veins numerous, parallel. Inflorescences of an axillary umbel, 3–5-flowered; peduncle ca. 3 mm, puberulent; bracts subulate, ca. 3 mm long, margin serrate, caducous. Pedicel 0.8–1 cm long, ± puberulent. Hypanthium campanulate-cupuliform, ca. 1 cm long, obtusely quadrangular, ± puberulent, with irregular horns up to ca. 3 mm long. Calyx lobes triangular, 3–4 × 1.5–2 mm, adaxially puberulent and strongly concave to nearly folded, abaxially convex and ridged, margin irregularly dentate, apex obtuse. Petals pink, broadly ovate, oblique, 1.4–1.6 × 0.9–1.1 cm, glabrous, apex acuminate. Stamens 8, antisepalous 4 longer, antipetalous 4 shorter, arranged in 2 whorls. Antisepalous stamens 2.0– 2.2 cm long; filaments pink, 1.0– 1.1 cm long, glabrous; anthers pink, lanceolate, strongly curved, 1.0– 1.1 cm long; connective slightly decurrent, basally with 2 ventral cream tubercles ca. 1.0– 1.2 mm long and a dorsal short cream spur ca. 0.7 mm long. Antipetalous stamens 1.2–1.4 cm long; filaments pink, 6–7 mm long, glabrous; anthers pink, lanceolate, strongly curved, 6–7 mm long; connective slightly decurrent, basally with 2 ventral yellow tubercles 1.0– 1.2 mm long and a dorsal short yellow spur ca. 0.7 mm long. Ovary inferior, urceolate to ovoid, quadrangular, ca. 8 × 4 mm, crown 4-lobed, apex irregularly denticulate with glandular trichomes; style white to pinkish, slightly curved, 1.6–1.7 cm long, glabrous, stigma obtuse. Capsule ovoid, obtusely quadrangular, ca. 8 × 4 mm. Seeds more than 100, ellipsoid, ca. 0.5 mm long.

Etymology:— The species is named after the country Vietnam where it was discovered.

Phenology:— Flowering from July to August; fruiting from August to March of next year.

Distribution and habitat:— The species is currently only known from a few localities in Lao Cai and Bac Kan, northern Vietnam. It grows at shady places under primary or secondary evergreen broad-leaved submontane forests on steep granite and quartzite slopes along streamside at elevations of 680–1350 m.

Conservation status:— The species was collected from several localities in Lao Cai and Bac Kan, northern Vietnam. All localities are protected areas of the Hoang Lien-Van Ban Nature Reserve and Kim Hy Nature Reserve . The new species grows at undisturbed sites and no anthropogenic threat has been detected. There are no data on population assessment in the field now. According to our prediction, the new species could be present in other locations with similar habitat conditions of the type locality. Therefore, it may be accessed to be ‘Data Deficient’ (DD) according to the IUCN Red List Categories and Criteria ( IUCN 2022).

Additional specimens examined (paratypes):— VIETNAM. Lao Cai Province: Van Ban District, Nam Xe Commune, 26 February 2001, Daniel K. Harder, Phan Ke Loc, Nguyen Tien Hiep, George E. Schatz, Sharon A. Bodine & Nguyen Quang Hieu DKH 6870 (HN, MO); Van Ban District , Nam Xay Commune , elev. 1200–1350 m, 1 km to the W of point 22°59’00’’N, 104°02’00’’E, 9 March 2002, L.Averyanov, P.K.Loc, Do Tien Doan HAL 2179 (HN); Van Ban District , Khanh Yen Ha Commune , elev. 680–880 m, around point 21°58’28’’N, 104°15’52’’E, 14 March 2002, L.Averyanov, Phan Ke Loc, Do Tien Doan HAL 2343 (HN); Van Ban District , Nam Xe Commune , elev. 1018 m, 22°03’28.1”N, 103°57’32.3”E, 1 July 2018, Do Van Hai, Zheli Lin, Sunan Huang HL 69 (HN, IBSC); ibid., 25 March 2019, Do Van Hai, Zheli Lin, Xixi Zhang HL 159 (HN, IBSC); ibid., 28 November 2019, Do Van Hai, Zheli Lin, Yuantao Xie HL 291 (HN, IBSC) . Bac Kan Province: Na Ri District, Kim Hy Commune , 17 August 2016, Do Van Hai et al., DVH 17082016 (HN) .

Taxonomic notes: —Until now, the genus Sporoxeia consists of eight species including the new species. Sporoxeia vietnamensis can be easily distinguished from other species of Sporoxeia by the stiffly papery leaf blades, larger and densely horned hypanthia, and larger calyx lobes and petals. Its horned hypanthia and nearly folded calyx lobes are uncommon in the Asian Melastomataceae . The horned hypanthia also occur to some species of Pternandra Jack (1822: 60) of the tribe Kibessieae , e.g., P. echinata Jack (1822: 3) . An identification key to the species of Sporoxeia is provided below.

Figures

FIGURE 1. Sporoxeia vietnamensis. A: flowering branch; B: flower, lateral view C. hypanthium, transverse section, showing obtusely quadrangular shape and 4-celled ovary; D: hypanthium, longitudinal section, showing urceolate ovary; E: flower, front view, showing eight subequal stamens; F: petals; G: antipetalous stamen (left) and antisepalous stamen (right), front view; H: antipetalous stamen (left) and antisepalous stamen (right), lateral view; I: ovary and style. Drawn by Le Kim Chi.

FIGURE 2. Sporoxeia vietnamensis. A: habitat; B: branch, showing spotted leaves; C: axillary inflorescences, showing subulate bracts and flower buds. Photos by Zheli Lin.

FIGURE 3. Sporoxeia vietnamensis. A: flowering branch; B: adaxial leaf surface; C: abaxial leaf surface; D: bracts; E: flower bud, lateral view; F: opening flower, lateral view; G: opening flower with petals removed, lateral view. H: opening flower, front view; I: petals; J: antipetalous stamen (left) and antisepalous stamen (right), lateral view; K: ovary and style; L: hypanthium, bottom view; M: hypanthium, front view, showing calyx lobes; N: hypanthium, longitudinal section, showing urceolate ovary; O: hypanthium, transverse section, showing obtusely quadrangular shape and 4-celled ovary; P: ovules; Q: obtusely quadrangular capsule with hypanthium removed. Photos by Do Van Hai.

FIGURE 4. Holotype of Sporoxeia vietnamensis.