Syzygium phamhoangii 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 : 252-253

Syzygium phamhoangii Tagane, V.S.Dang & Yahara , sp. nov. ( Figure 3 ).

TYPE:— VIETNAM. Khanh Hoa Province, Mt. Hon Ba, 12°06′46.88″N, 108°58′14.43″E, elev. 919 m, 20 Feb. 2014, Toyama H., Dang V.S., Tagane S., Fuse K., Yahara T., Nagamasu H., Tran H., Nguyen V.N., Nguyen Q.C., Do N.T. & Ho N.P.H. V909 [fl.] (holotype KYO!, isotypes FOF!, KAG!, VNM!, the herbarium of Hon Ba Nature Reserve).

Syzygium phamhoangii is similar to Syzygium balsameum ( Wight 1841: 16) Walpers (1843: 179) in the shape of leaves and axillary inflorescences but distinguished by its obtuse to slightly cordate leaf base (vs. cuneate to long attenuate), shorter petioles ((1–) 2–4 mm long vs. 4–15 mm long), larger hypanthium (3.5–4 mm long vs. 2.5–3.5 mm long) and more ovules per locule in ovary (12–16 ovules vs. 3–8 ovules).

Shrub, 1.5 m tall. Young twigs slightly compressed, yellowish to reddish brown, old twigs terete, yellowish brown, glabrous, internode (1.5–) 2.5–7.4 cm long. Leaves opposite, blade elliptic-oblong, (5–)9.3–17 × (2.2–) 3.4–6.5 cm, 2.1–3.5 times longer than wide, thinly coriaceous, grayish green to dull brownish yellow adaxially, light yellowish brown abaxially, glabrous on both surfaces, apex acuminate, acumen to 1.5 cm long, base obtuse, rounded, slightly cordate, margin entire, slightly recurved when dry, midrib sunken adaxially, prominent abaxially, secondary veins 10–12 pairs, (0.5–) 1–2.1 cm apart, slightly prominent abaxially, intersecondary veins usually distinct, tertiary veins indistinct on both surfaces, intramarginal vein 1, outer one ca. 0.8 mm from margin, inner one ca. 5 mm apart from margin; petiole (1–) 2–4 mm long, glabrous. Inflorescences axillary on leafy twig, paniculate, 4–5.8 cm long, 18–48 flowered, peduncle up to 1.3–1.9 cm long, rachis and lateral branches slightly compressed, bracteoles triangular, ca. 1.1 mm long, apex acute, glabrous, caducous. Flower bud ca. 2 mm in diam., whitish (in vivo). Hypanthium funnel shaped, 3.5–4 mm long, reddish brown when dry, glabrous, sessile. Sepals 4, broadly triangular, ca. 0.5 × 1.5 mm, petals 4, orbicular, ca. 2 mm in diam., membranous, 3 gland dots per petal. Stamens 44–50, 1.7–3 mm long, anthers ca. 0.6 mm long, filaments white (in vivo), 1.2–2.4 mm long. Style ca. 2 mm long. Ovary 2-locular, ovules 12–16 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. 920 m elevation.

Phenology:— Flowering specimens were collected in February.

Etymology:— The specific epithet is chosen in honor of the excellent Vietnamese botanist Prof. Dr. Phạm Hoàng Hộ, who significantly contributed to the study of the flora of Vietnam.

Vernacular name:— Trâm phạm hoàng hộ.

Preliminary conservation assessment:— Critically Endangered (CR). Syzygium phamhoangii is known only from a single population in Mt. Hon Ba, at ca. 900 m above the sea level. The population with fewer than 15 mature individuals is very close to the road and can be easily affected by human disturbance. Therefore, this species is qualified as CR under criterion D ( IUCN 2012).

Figures

FIGURE 3. Syzygium phamhoangii Tagane, V.S.Dang & Yahara.A) Leafy branch, B) Flowering branch, C) Portion of lower leaf surface, D) Inflorescence, E) Flowers. Photographs: A–E for Toyama et al. V909, taken by S. Tagane on 20 Feb. 2014.