Syzygium honbaense Tagane, V.S.Dang & Yahara, 2018

Tagane, Shuichiro, Dang, Van-Son, Souladeth, Phetlasy, Nagamasu, Hidetoshi, Toyama, Hironori, Naiki, Akiyo, Fuse, Kengo, Tran, Hop, Yang, Ceng-Jui, Prajaksood, Amornrat & Yahara, Tetsukazu, 2018, Five new species of Syzygium (Myrtaceae) from Indochina and Thailand, Phytotaxa 375 (4), pp. 247-260 : 251-252

Syzygium honbaense Tagane, V.S.Dang & Yahara , sp. nov. ( Figure 2 ).

TYPE:— VIETNAM. Khanh Hoa Province, Mt. Hon Ba, 12°07′29.45″N, 108°57′51.11″E, elev. 1204 m, 21 July, 2013, Tagane S., Yahara T., Nagamasu H., Fuse K., Toyama H., Tran H., Dang V.S., Loi X.N., Thach N.D., Cuong Q.N., Hieu P.N.H. & Thach K.N. V612 [fl.] (holotype KYO!, isotypes KAG!, VNM, the herbarium of Hon Ba Nature Reserve).

Syzygium honbaense is distinct from all the other Syzygium species in the region by having terminal inflorescences with 3 to 5 reddish flowers, ca. 1.1 cm long hypanthium and relatively smaller leaves, to 7.2 × 2.7 cm.

Tree, 10 m tall. Young twigs terete, grayish brown, glabrous, ca. 1 mm in diam., old twigs grayish brown, internode (0.5–) 1.2–2.6 cm long. Leaves opposite, blade elliptic, elliptic-oblong, rarely obovate, (1.7–)2.6–7.2 × (0.8–)1.2–2.7

cm, 1.8–3.2 times longer than wide, coriaceous, dark yellowish green to grayish green adaxially, dull brownish yellow abaxially, glabrous on both surfaces, base cuneate, apex acuminate or acute, margin entire, slightly recurved when dry, midrib sunken adaxially, prominent abaxially, secondary veins 8–10 pairs, prominent on both surfaces, intersecondary veins distinct adaxially, intramarginal veins 1 (rarely 2, faintly visible), 1–2 mm apart from margin; petiole (0.4–) 0.8–1 cm long, concave adaxially, rounded abaxially, grayish green to yellowish brown, glabrous. Inflorescences terminal, racemose, 3- to 5-flowered, rarely solitary, peduncle 0.8–1.4 cm long, rachis and lateral branches terete or occasionally slightly compressed; bracteoles caducous, not seen. Flower buds subglobose, ca. 1.1 cm in diam., reddish purple (in vivo). Hypanthium funnel-shaped, ca. 1.1 cm long, glabrous, pseudostipe indistinct, or very short to 1 mm long. Sepals 4, depressed ovate, 2.5–4 × 7–8 mm, apex rounded, margin fringed with whitish, membranous part, petals 4, suborbicular, ca. 9 mm in diam., membranous, with ca. 180 gland dots per petal. Stamens many, more than 340, 1.1–1.5 cm long, anthers 0.8–0.9 mm long, filaments reddish purple (in vivo), glabrous. Style ca. 1.4–1.7 cm long, glabrous, ovary 2-locular, ovules 18–20 per locule. Fruit and seeds not seen.

Distribution:— Vietnam (so far only known from the type locality, Mt. Hon Ba).

Habitat and Ecology:— Hill evergreen forest, at ca. 1200 m elevation.

Phenology:— Flowering specimens were collected in July.

Etymology:— The new species is named after the type locality, Hon Ba Nature Reserve in Khanh Hoa Province of Vietnam.

Vernacular name:— Trâm hòn bà.

Preliminary conservation assessment:— Critically Endangered (CR). During our intensive botanical surveys in Mt. Hon Ba from 2011 to 2013, only one flowering individual was found at the edge of the evergreen forest, along the road to the summit of Mt. Hon Ba. This situation satisfies the CR (critically endangered) status in criterion D of IUCN Red List Categories ( IUCN 2012).

Note:— Among the Syzygium species having relatively large (hypanthium> 1 cm in diam.) and reddish to purplish flowers in Indochina, S. honbaense is easily distinguished from the other species by a combination of its smallest leaves ((1.7–) 2.6–7.2 cm long vs. longer than (6–) 12 cm) and terminal inflorescences.

Figures

FIGURE 2. Syzygium honbaense Tagane, V.S.Dang & Yahara. A) Habit, B) Flowering branch, C) Bark, D) Lower leaf surface, E) Inflorescence, F & G) Flowers, H) Flower after anthesis showing hypanthium, sepals and style; Stamens and petals fallen. Photographs: A–H for Tagane et al. V612, taken by S. Tagane on 21 July 2013.