Phyllagathis phamhoangii V.T.Pham, T.C.Vu & Ranil, 2017

Pham, Van The, Vu, Tien Chinh, Rajapaksha, Ranil, Trinh, Ngoc Bon, Averyanov, Leonid & Nguyen, Thi Lien Thuong, 2017, Phyllagathis phamhoangii (Sonerileae, Melastomataceae), a new species from central Vietnam, Phytotaxa 314 (1), pp. 140-144 : 141

Phyllagathis phamhoangii V.T.Pham, T.C.Vu & Ranil , sp. nov. ( Fig. 1 )

Type:— VIETNAM. Quang Nam Province, Dai Loc District, Dai Hong Municipality, environs of Dai Hong town , on large shady mossy boulders on very steep humid rocky slope in rich secondary broad-leaved evergreen forest, 500 m, 15°49’44”N 107°57’19”E., 19 May 2011, L.Averyanov, P.K.Loc, N.Q.Hieu, P.V.The, N.T.Vinh, CPC 3419, (holotype: HN!; isotype: LE!) .

Acaulescent rhizomatous herb, with leaves up to 25 cm tall, sparsely hairy in all parts except petals and stamens, fewer on the leaves. Rhizome creeping to suberect, tuberous, orange-brown setose, 1.5 cm in diameter, with conspicuous leaf scars. Leaves 3–5, petiolate; petiole 14–17 cm long; leaf blade cordate to reniform, 7–11 cm wide, 8–13.5 cm long, at base cordate, apex shortly acuminate, margin finely denticulate; lamina with 4 pairs of basal veins and a midrib, membranous, adaxial surface often light green, abaxial surface often light purple with prominent veins. Inflorescence a dichasial cyme; peduncle reddish, 14.5–18.5 cm long, cylindrical, usually longer than petioles, with minute glands. Flowers 4-merous, subtended by a few subulate bracts 1.5–2 mm long; pedicel ca. 1 cm long, with minute glands. Hypanthium campanulate, 4-ridged, about 6–7 mm long and 2.8 mm wide, with minute brown glands. Sepals triangular, about 0.5 mm long, acute. Petals pink, broadly obovate to almost round, obtuse or, shortly acuminate, glabrous, 6.5–7 mm long, 8.5–9 mm wide. Stamens 8, dimorphic, unequal in length, arranged in 2 whorls; antesepalous stamens 4, filaments 7.5–8 mm long, glabrous, anthers narrowly ovate, glabrous, 6.5–7 mm long, light violet, strongly curved on ventral side, connective with an inflated base, ventrally with two laterally compressed lobes, pore 1, apical, more or less oblique on the ventral side; antepetalous stamens 4, filaments 5.5 mm long, anthers narrowly ovate, 2.5 mm long, yellow, glabrous, connective with a short dorsal spur. Ovary 4-locular, ca. 2.5 mm long, a little longer than one third of hypanthium length, crown consisting of four thick connate lobes. Styles ca. 7 mm long. Capsules subquadrangular, cup-shaped, about 3 mm wide and 4–5 mm long (when dry), crown persistent. Seeds numerous, ca. 0.25 × 1 mm (when young), narrowly conical, glabrous.

Phenology:— Flowering was observed in April to May. Fruiting started in May.

Diagnostic characters:— The described species is closely allied to P. nanakorniana from Thailand and P. subrotunda from north of Vietnam in habit and some morphologic characters, such as the tuberous rhizome and leaf shape. However, it differs from P. nanakorniana in the sparse hairs on all of its parts except petals and stamens, much longer petioles, dichasial inflorescences, longer hypanthia, stamens unequal in length, longer petals and ovary. It differs from P. subrotunda by the taller plants, smaller leaves with longer petioles, cordate to reniform blades with a shortly acuminate apex, dichasial inflorescences, longer and cylindrical peduncles, longer and narrower hypanthia. The detailed comparison between P. phamhoangii , P. nanakorniana and P. subrotunda are given in Table 1.

Distribution:— The species is only known from Quang Nam and Quang Binh Provinces of Vietnam ( Fig. 2 ).

Habitat and ecology: — The new species grows in rich secondary broad-leaved evergreen forests at an elevations of 400–500 m as a lithophytic herb on large wet mossy boulders and cliffs composed of eroded sandstone on steep slopes.

Conservation status:— Phyllagathis phamhoangii was recorded only from two small subpopulations in Quang Nam and Quang Binh provinces of Vietnam. Though it is locally abundant, existing populations are facing a risk of extinction in the wild, since the areas where this species is found do not belong to any protected forest. The habitats are highly disturbed by local people for collecting timber, fire-wood and non-timber forest products. In addition, the new species has beautiful plants and flowers, and may be used as ornamental and collected by local people in the future. The estimated total known area of its distribution is less than 20.000 km 2, in habitats that are seriously threatened. Based on our information, we propose a conservation status of P. phamhoangii as Vulnerable (VU) under IUCN criteria B1 a b(iii) ( IUCN 2017).

Etymology:— The species is named after Prof. Pham Hoang Ho, who spent most of his life studying the flora of Vietnam. He has published many books on the flora which are useful for students, teachers and researchers all over Vietnam.

Vernacular name: —Vietnamese: Me nguồn phạm hoàng hộ

Additional specimen examined:— VIETNAM. Quang Binh province, Minh Hoa District, Dan Hoa Municipality, Giang Man Mountain, Vietnam-Laotian border, about 6 km to N of Cha Lo border station, ca. 1100 m, 17º41’09’’N, 105º45’54’’E, 21 April 2008, L. Averyanov, P.K. Loc, N.T. Vinh, N.S. Khang, HAL 11790 (HN!, HNU!, MO!, LE!).

Figures

FIGURE 1. Phyllagathis phamhoangii V.T.Pham,T.C.Vu & Ranil.a. flowering plant in its natural habitat.b. flattened flowering specimen. c. portion of stem. d. leaf adaxial surface. e. leaf abaxial surface.f. leaf blade margin, adaxial surface. g. leaf blade margin, abaxial surface. h, i. inflorescence. j, k. petals adaxial (left) and abaxial (right) views. l, n. removed stamens. m. intact stamens. o. removed antepetalous stamen. p. style. q. style and ovary, longitudinal section. r. flower bud. s. petals, transverse section of flower bud, view from below. t. transverse section of flower bud, view from above. u. inflorescence with flower buds and young fruits. v. young fruit, view from above. w. young fruit transverse section. x. young fruit longitudinal section. y. young seeds. z. scape apex. Scale bars: a, b, d, e = 5cm; c = 1cm; f, g, h, i, j, k, m = 0.5cm; l, n, o, p, q, r, s, t, v, w, s, y = 1 mm; u = 5 mm; z = 2 mm. Photos and design by Pham Van The based on the type, HAL 11790 (LE, VNMN).

FIGURE 2. Distribution of Phyllagathis phamhoangii V.T.Pham, T.C.Vu & Ranil. Locations in Quang Binh and Quang Nam provinces are marked by black rounds.