Sonerila dongii D. D. Nguyen & C. W. Lin. A. Habit 2024, sp. nov.
Creators: name: Nguyen, Danh Duc
name: Nguyen, Van Canh
name: Lin, Che Wei
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Melastomataceae
Sonerila
Sonerila dongii

description: Sonerila dongii D.D.Nguyen & C.W.Lin, sp. nov. (Figs. 1−3)
Type: — VIETNAM. Lam Dong province: Duc Trong district, growing on mossy granite stone boulders in semi-shaded areas near seasonal waterfall in Ta Nang commune, ca. 1,200 m elevation. Specimens were pressed from plants originally collected by Nguyen Danh Duc and Truong Nguyen Dong on 29 June 2018, and grown in the variegated plant nursery (Dong Nai province) owned by Mr. Truong Nguyen Dong, 2 December 2020, Nguyen Danh Duc NDD- 499 (holotype VNMN!; isotype LE!).
Diagnosis: Sonerila dongii resembles the Thailand endemic S. peninsularis J.Wai & J.M.Hu (2023: 122) in its variegated ovate foliage and stems and inflorescence covered with minutely brown glandular trichomes. However, the new species is readily distinguished from S. peninsularis by its non-tuberous habit (vs. tuberous), terete and branched stem (vs. quadrangular and usually unbranched), glabrous petals (vs. abaxial surface with long stipitate glandular trichomes) and longer anthers by 4.5–5 mm (vs. 1.5–2.5 mm) long.
Perennial lithophytic herbs. Stems ascending, rooting at lower nodes when procumbent, branching, stout, reddish-brown to olive green, terete, 5–8 mm thick, fleshy, with dense, minute, glandular trichomes, translucent when young, becoming brown when mature; internodes 0.8–3.5 cm long. Leaves decussate, isomorphic; petiole sub-terete, grooved above, yellowish-green to pale reddish-brown, 0.3−1.2 cm long, 3−4 mm across, glabrous or with sparse, minute, glandular trichomes; leaf blades thick, chartaceous, slightly succulent, symmetric, ovate to widely elliptic, rarely lanceolate, 4−9.8 × 2.7–5.6 cm, base subcordate to cuneate, apex acute to attenuate, margin denticulate with each tooth tipped by a short trichom, adaxially very sparsely puberulous, maroon to dark bluish-brown, adorned with irregular, olive-green to greyish-green semi-continuous spots of variable sizes between the midrib and margin, spots becoming more dense towards the inner side, forming a light-colored zone along the midrib, sometimes accompanied by sparsely silvery green dots, margin with a narrow greyish-green rim 1–2 mm wide, subvelutinous, abaxially glabrous, purplish-red to magenta, with whitish-green irregular splash spots corresponding to the pattern on adaxial surface; venation acrodromous, primary vein shallowly grooved above. Inflorescences terminal or axillary, scorpioid cymes, 6–18-flowered; peduncles pinkish-brown to yellowish-red, 3.5–5 cm long, erect to ascending, covered with minute transparent brown glandular trichomes; bracts minutely narrowly triangular, ca. 0.3 mm long. Flowers 3-merous; pedicels pinkish-brown to yellowish-red, 3–6 mm long, densely covered in minute, transparent, brown, glandular trichomes. Hypanthium cylindrical to narrowly campanulate, 4.3–6.5 × 2.2–2.8 mm, dusky magenta, purplish-brown to reddish-brown, with dense, minute, transparent, brown, glandular trichomes; ca. two-fifths of hypanthium free from the ovary. Sepals 3, widely triangular, 1.3–1.7 × ca. 2.2 mm, apex acuminate. Petals widely oblong-ovate, 11–15 × 7.5–9 mm, apex acuminate, rosy pink to rich magenta, glabrous. Stamens 3, equal; filaments 7–9 mm long, magenta, glabrous; anthers lanceolate, slightly incurved, deeply cordate at base, apex attenuate, 4.5–5 mm long, golden yellow, apex opening with two pores. Ovary 4–4.5 mm long, 3-locular; ovary crown crescent-shaped to widely oblong, ca. 1.3 mm high, margin denticulate; ovules numerous; style 11–15 mm long, magenta; stigma capitate, papillate, white. Capsule not seen.
Distribution & IUCN preliminary assessment: —Despite extensive investigations in southern Vietnam, where the first author conducted research, only a few individuals of this new species have been discovered in the highlands of South Vietnam (Fig. 4) at elevation of around 1,200 meters. Future expeditions are expected to provide more clarity on the status of this species. The current status of S. dongii is proposed to be Data Deficient (DD) following the IUCN Red List Categories and Criteria (2024).
Ecology and phenology: —It grows on wet granite stone cliffs along the bank of a waterfall in evergreen broadleaved forest mixed with pine forest, and is typically found in semi-shaded areas. This species blooms mainly from July to September and enters dormancy from January to March. Its growth cycle in greenhouse cultivation closely resembles that in its natural habitat, however, the flowering period may extend due to cultivation conditions. Whether in its natural habitat or in experimental greenhouses, leaf fall and dormancy occur during winter.
Etymology:— The specific epithet is named after Mr. Truong Nguyen Dong, who cultivated the type specimen of this new species until it flowered. He is a young enthusiast of ornamental plants and operates a nursery in Long Thanh City, Dong Nai province, where he grows a variety of wild plants collected from across Vietnam, including begonias, aroids, and gingers, among others.
Note:— Unlike any known Indochinese Sonerila species with a periodically dormant habit, the new species, Sonerila dongii lacks a tuber but has a thick and fleshy stem, the habit is similar to some sympatric orchids such as Ludisia discolor (Ker Gawl. 1818: 271) Blume (1859: 95) (figure 3: A & B) or certain species of Cheirostylis Blume (1825: 16). Sonerila dongii exhibits great horticultural potential, attributed to its colorful, variegated leaves, relatively compact growth habit, and excellent adaptability to various environmental conditions. The new species bears a superficial resemblance to S. peninsularis but is distinct due to its non-tuberous habit, terete stem, glabrous petals, and longer anthers. A detailed comparison of the two Sonerila species is presented in Table 1.
Specimens examined (Paratype): — VIETNAM. Lam Dong province: Duc Trong district, growns on mossy granite stone boulders in semi-shaded areas near seasonal waterfall in Ta Nang commune, ca. 1,200 m elevation. Specimens were pressed from plants grown in experimental greenhouse at the Taipei Botanical Garden, 15 July 2024, C.W.Lin 722 (TAIF!).
description: Published as part of Nguyen, Danh Duc, Nguyen, Van Canh & Lin, Che Wei, 2024, Sonerila dongii (tribe Sonerileae, Melastomataceae), a new species from Lam Dong province, South Vietnam, pp. 149-156 in Phytotaxa 663 (3) on pages 150-155, DOI: 10.11646/phytotaxa.663.3.4, http://zenodo.org/record/14515655