Nephoanthus nubigenus C.W.Lin, Luu & T.C.Hsu, 2022

Lin, Che-Wei, Hsu, Tian-Chuan, Luu, Hong Truong, Yang, Tsung-Yu Aleck & Li, Chia- Wei, 2022, Nephoanthus (Melastomataceae: Sonerileae), a new genus segregated from Phyllagathis s. l., with a new species from Southern Vietnam, Phytotaxa 547 (1), pp. 66-76 : 70

1. Nephoanthus nubigenus C.W.Lin, Luu & T.C.Hsu , sp. nov. ( Figs. 4 & 5 ).

Type: — VIETNAM. Khanh Hoa Province: Khanh Vinh District, Son Thai Commune , 12°12’59.4”N, 108°44’54.5”E, ca. 1,000 m elev., 23 September 2018, T. C . Hsu 10952 (holotype TAIF-537150!; isotype: SGN!) .

Diagnosis: — Nephoanthus nubigenus resembles N. prostratus in terms of habit, inflorescence structure and morphology of stamens but is readily distinguishable in having apically ascending (vs. creeping) stems, adaxially slightly bullate (vs. densely rugose), uniformly green (vs. silvery striped or dotted) and sparsely shortly hirsute (vs. densely long pilose) laminae, glabrous or subglabrous (vs. pilose) peduncles, 5-merous (vs. both 4 and 5-merous) flowers and yellow (vs. orange to orangish-magenta) anther appendages.

Perennial caulescent herbs, terrestrial. Stems poorly branched, rooting at lower nodes and creeping, erect or ascending in upper part of the twigs; olive green to reddish brown, to 15 cm or longer, 0.4–0.9 cm diam.; terete or inconspicuously ribbed in young stems, 6-ribbed when older; slightly woody at base, sparsely covered with white to pale-brown velutinous trichomes 1–3 mm long; internodes 1.2–5 cm long. Leaf blades ca. 3 pairs on each branch, decussate, 6–11 × 4–7 cm, isophyllous, widely ovate, base subcordate, margin denticulate, ciliate, apex shortly acuminate; chartaceous; adaxially green, sparsely shortly hirsute between veins, trichomes 0.5–1 mm long; abaxially pale green, velutinous on all veins, trichomes 0.5–2 mm long, appressed or curved towards the apex; venation acrodromous. Nerves 7 veined, basal; veins slightly depressed on the adaxial surface and prominent on the abaxial surface, secondary and tertiary veins numerous and conspicuous, reticulate. Petioles 1.5–2.5 cm long, subterete and slightly grooved adaxially, densely velutinous. Bracts hyaline, persistent, largest pair ovate to widely ovate, 14–18 mm long, 6–13 mm wide, apex attenuate, sparsely velutinous on abaxial surface, margin ciliate, becoming oval-lanceolate or lanceolate, smaller towards the inflorescence interior. Inflorescences terminal, umbelliform and nearly capitate when young, peduncle 1.4–2.5 cm long, glabrous or very sparsely hirsute. Flowers pentamerous, pedicels 2–3 mm long, densely short villous and long hirsute. Hypanthium campanulate, 3–3.8 mm long, 2–2.5 mm diam., sparsely short villous and long hirsute; terete or slightly 10-ribbed. Sepals 5, narrowly triangular to lanceolate, apex aristate, each sepal with a subapical fleshy trichome, trichomes multi-branched, 1.5–2.5 mm long; sepals connate at the base and forming a ring, with an acute triangular external tooth on the notch between sepals, each tooth tipped by a long seta, trichomes branched; perishing with the tubular part of hypanthium shortly after flowering. Petals 5, oblique, glabrous, widely elliptic to oblong, ca. 7 mm long, 4 mm wide, rosy pink, apex mucronate apiculate. Stamens 10, isomorphic, filaments slightly flat, ca. 6.5 mm long, white, pink tinged toward base, anthers subulate, apex attenuate, slightly curved ventrally, 3–4 mm long, pinkish to purplish, pore 1, connective extended for ca. 0.5 mm below anther sacs widening basally and produced into an ovate, yellow spur dorsally and into two erect, narrowly triangular, yellow lobes ventrally. Style 10–13 mm long, pinkish, stigma capitate. Ovary ca. 1/2 as long as the hypanthium, crown with fully connate lobes, margins entire or slightly repand, anther pockets shallow, placentae stalked. Capsules on pedicels ca. 5 mm long, hypanthium cupshaped, 10-ribbed, ca. 4.5–6 × 4–5 mm, placental column distally horned, placentas thready.

Distribution and ecology: — Nephoanthus nubigenus is endemic to Southern Vietnam. Currently it is only known from the type locality in Khanh Hoa Province, where it grows under humid and cloudy broadleaved forests on mountain slopes at an elevation of 1,000 –1,041 m.

Etymology: —The specific epithet nubigenus means “cloud-born”, referring to the foggy habitat where the new species has been found.

Additional specimens examined (paratypes): — VIETNAM. Khanh Hoa Province: Khanh Vinh District, Son Thai Commune , 12°13’1.34”N 108°44’49.99”E, 1,041 m elev., 12 November 2012, H. T . Luu & G . Tran KH277 ; KH278 ; KH279 ( SGN!) .

Taxonomic remarks: — Nephoanthus nubigenus shares similar floral structure with N. prostratus , but the two species are vegetatively quite distinct. A detailed morphological comparison between the two species is presented in Table 2.

Figures

FIGURE 4. Nephoanthus nubigenus C.W.Lin, Luu & T.C.Hsu. A. Habit; B, B’. Portion of leaf, adaxial and abaxial surfaces; C. Cross section of stem, showing 6-ribs; D. Inflorescence; E, E’. Bracts; F, F’. Flower, face and side views; G. Petal; H, H’, H’’. Stamens, side, ventral and dorsal views; I. Style; J. Hypanthium, top view; K, K’. Old capsule, top and side views.

FIGURE 5. Nephoanthus nubigenus C.W.Lin, Luu & T.C.Hsu. A. Habit and Habitat; B. Habit; C. Flowering branch; D, E. Portion of leaf adaxial and abaxial surfaces; F. Petioles, also showing stem and peduncle; G. Bracts; H. Flower, face and side views; I. Hypanthium; J. Old capsule, top view; K. Old capsules; L. Longitudinal section of an old capsule. All photos from T.C.Hsu 10952 (TAIF), A−K by Tian-Chuan Hsu, L by Che-Wei Lin.