Nephoanthus C.W.Lin & 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 : 67-69

Nephoanthus C.W.Lin & T.C.Hsu gen. nov.

Type: — Phyllagathis prostrata Hansen (1990: 39) .

Diagnosis: — Nephoanthus resembles Tigridiopalma in the herbaceous habit, ovate leaves and stamens with the decurrent connective of anthers forming an spur dorsally and two erect lobes ventrally. However, it is distinct from Tigridiopalma in its much smaller foliage by 3–11 × 1.7–7 cm (vs. 20–51.8 × 13.6–44.9 cm), umbellate (vs. scorpioid) inflorescences, terete or slightly 8- or 10-ribbed (vs. 5-winged) hypanthia, isomorphic (vs. dimorphic) anthers, and old capsules with distally horned (vs. not horned) placental columns and thready (vs. non-thready) placentas.

Herbs caulescent, perennial. Stems slender, terete or ribbed, basally creeping, rooting at nodes and branched, apically creeping or ascending, velutinous or hirsute. Leaves opposite, isomorphic, equal to subequal, 7-nerved, ovate to broadly ovate, velutinous or hirsute, trichomes 0.5–1.5 mm long, upper surface flat to rugose, base cordate, apex acuminate to rounded, margin denticulate or crenulate, ciliate. Petioles subterete and slightly grooved adaxially, pilose, trichomes 2–5 mm long. Inflorescences terminal or rarely axillary, umbellate, nearly capitate, peduncles short, glabrous or sparsely hirsute, bracts persistent, deltoid, ovate to cordate, apex attenuate to obtuse, abaxial surface hairy, margin ciliate. Flowers 4- or 5-merous, shortly pedicellate. Hypanthium cup-shaped, terete or slightly 8- or 10-ribbed, pilose. Sepals triangular and keeled, apex aristate, each with a subapical fleshy trichome, trichomes multi-branched, 1.5–2.5 mm long; sepals connate at the base and forming a ring, hirsute; perishing with the tubular part of hypanthium shortly after flowering. Petals oblique, elliptic, obovate to oblong, rosy pink, apex mucronate-apiculate, glabrous or with a few apical glandular trichomes dorsally. Stamens isomorphic, filaments slightly flat, white to purplish-red, anthers subulate, apex attenuate, slightly curved ventrally, pale pink to purplish, pore 1, connective extended below anther sacs and forming an ovate, yellow or orangish-red spur dorsally and two erect narrowly triangular, yellow or orangishred lobes ventrally. Style white to pink, stigma capitulate; Ovary ca. 1/2 as long as the hypanthium, crown with fully connate lobes, margin entire or denticulate with some minute uni-seriate glandular trichomes, anther pockets shallow, placentae stalked. Capsules shortly pedicellate, hypanthium cup-shaped, 8 or 10-ribbed, placental column distally horned, placentas thready. Seeds numerous, pale brown, cuneate, 0.3–0.4 × 0.15–0.2 mm.

Etymology: —The generic epithet is derived from Greek nephos, cloud, and anthus, flower, referring to the cloud forest habitat where species of this genus grow.

Distribution: — Vietnam and China (Hainan Island) ( Fig. 1 ).

Taxonomic remarks: —The gross morphology of Nephoanthus is somewhat similar to Phyllagathis rotundifolia , the type species of Phyllagathis , as they share dwarf herbaceous habits, basally creeping stems and nearly capitate inflorescences embraced by large persistent bracts ( Fig. 2 , A & B). However, Nephoanthus is distinguishable by the absence of stellate minute brown glands on vegetative organs, pink to purplish anthers, and also by the presence of a pair of ventral appendages at the base of the anther sac. Because molecular data ( Zhou et al. 2019a; 2019b; 2019c; Zeng et al. 2021) strongly supports the fact that Nephoanthus and P. rotundifolia are in different major clades within Sonerileae , their morphological similarities are either symplesiomorphies or the result of parallel evolution. Within the superclade recognized in Zhou et al. (2019c; also see INTRODUCTION), Nephoanthus is morphologically most similar to Tigridiopalma ( Fig. 2 , C–E) but it is easily distinguished by its much smaller foliage by 3–11 × 1.7–7 cm (vs. 20–51.8 × 13.6–44.9 cm), umbellate (vs. scorpioid) inflorescences, terete or slightly 8- or 10-ribbed (vs. 5-winged) hypanthia, isomorphic (vs. dimorphic) anthers, and old capsules with distally horned (vs. not horned) placental columns and thready (vs. non-thready) placentas. A detailed comparison between Nephoanthus and phylogenetically allied taxa ( Fig. 3 ) is presented in Table 1.

Figures

FIGURE 1. Distribution map of Nephoanthus nubigenus (yellow star) and N. prostratus (pink circle).

FIGURE 2. Two taxa morphologically similar to Nephoanthus: Phyllagathis rotundifolia (A & B); Tigridiopalma magnifica (C−E). A. Habit; B. Inflorescence; C. Habit; D, E. Flower, face and side views. A & B by Che-Wei Lin; C−E by Wei-Yen Chen.

FIGURE 3. A selection of taxa within the superclade recognized by Zhou et al. (2019c) that contains Nephoanthus, showing varied habits and morphological characters: Driessenia inaequalifolia (M), D. phasmolacuna (K & L); Medinilla laxiflora (B), M. speciosa (G & H), M. sp. (I & J); Phyllagathis gymnantha (N), P. rajah (A, C & D), P. stellata (E & F). A. Terrestrial in lowland mixed dipterocarp forest; B. Understory epiphyte on tree trunks and branches; C. Pleiochasium; D. Side view of flower, appendages firmly connected with the anther sacs, concolorous, hypanthium 10-ribbed; E. Umbelliform inflorescence; F. Side view of flower, anthers with concolorous appendages, connective slightly prolonged below anther sacs, hypanthium 10-ribbed; G. Paniculate inflorescence; H. Face view of flower, appendages firmly connected with the anther sacs, discolorous; I. Paniculate inflorescence; J. Face view of flower, appendages firmly connected with the anther sacs, concolorous; K. Thyrse, also showing the old capsule as empty cups; L. Face view of flower, anthers with concolorous appendages, connective slightly prolonged below anther sacs; M. Old capsule as empty cups; N. Old capsules, ovary with 4-horned placental column, placentas thready.All photos by Che-Wei Lin.