Syzygium samianum W.K.Soh & J.Parn., 2024

Soh, Wuu Kuang, Sam, Hoang Van & Parnell, John A. N., 2024, Three new species of Syzygium Gaertn. (Myrtaceae) from Cambodia and Viêtnam, Adansonia (3) 46 (4), pp. 29-36 : 32

Syzygium samianum W.K.Soh & J.Parn. , sp. nov.

( Fig. 2 )

A species morphologically similar to Syzygium sublaetum (Craib) Byng & Christenh. in the distinct tertiary veins, the pyriform hypanthium with distinct pseudostalk, the racemose inflorescence and the pedicellate flowers but can be distinguished from this species by the relatively small leaves ( S. samianum : 2.5-5 × [0.7-] 1.2-2.5 cm; S. sublaetum : 5.5-12 × 2-4 cm), straight intramarginal veins ( S. sublaetum : looped intramarginal veins), the relatively short pedicel ( S. samianum : 1-2 mm long; S. sublaetum : 5-45 mm long) and the relatively small hypanthium ( S. samianum : [5.5-]7-8 × [4-] 5-6 mm; S. sublaetum : 8.8-11 × 5.5-6.7 mm).

TYPE MATERIAL. — Viêtnam • Khánh Hòa province [Pro. Nha Trang], peninsula of Mt Hòn Hèo; 3.V.1923; Poilane 6237; holo-, P [ P01065741 ]!, iso-, P [ P01065739 , P06871647 , P00855380 ]!).

ADDITIONAL SPECIMENS EXAMINED. — Viêtnam • West of Nhatrang , between [Song -tan] and [D’out]; 1500 m a.s.l.; 27.V.1922; Poilane 3781; P [ P04884449 ] !).

ETYMOLOGY. — This particular species is named in honour of Dr Hoang Van Sam, a botanist affliated with the Vietnam National University of Forestry, who has significantly contributed to advancing our knowledge of the Vietnamese flora and to train emerging botanists in the country.

DISTRIBUTION. — Endemic to Viêtnam, so far known only in the South-central Viêtnam in the Khánh Hòa province including the Hòn Hèo peninsula.

HABITAT. — This species occurs in both lowland and highland habitats: one gathering was collected at the peninsular of Mt Hòn Hèo between 350 and 500 m elevation, which habitat would likely be hill evergreen forest. Another specimen was collected in the same province at 1500 m elevation on rocky, peaty and acidic soil, which altitude would infer a habitat dominated by montane forest.

PHENOLOGY. — Flowers were collected in May.

CONSERVATION STATUS. — Near Threatened (NT) ( IUCN 2012). On the satellite imager in Google Earth (images taken between 2018 and 2021), the landscape at Mt Hòn Hèo and the areas above 1000 m elevation in Khánh Hòa province appear to be arboraceous. The forest at Mt Hòn Hèo is protected. The estimated Extent of Occurrence which ranges from Mt Hòn Hèo to the west of Khánh Hòa province is approximately 3600 km 2. However information on the exact location and habitat quality is not available to satisfy either the Critically Endangered, Endangered or Vulnerable criteria. Therefore the species is provisionally evaluated as Near Threatened (NT).

DESCRIPTION

Shrub, 2.5 m tall, trunk 6 cm diameter, glabrous. Twig terete, 1.5-2.5 mm diameter, slender, surface smooth, pale brownish, not contrasting to leaf colour. Leaves opposite, coriaceous, brownish, 2.5-5 × (0.7-) 1.2-2.5 cm, 1.5 to 3.5 times as long as wide, elliptic, obovate, oblong-elliptic, oblongobovate, base cuneate, slightly attenuate, margin revolute, apex acute, blunt, acumen indistinct; midrib sunken above, raised below; secondary veins very slender, 11-15 per side, narrowly spaced, 1.5-3 mm apart, 40-55 degrees from midrib, prominent, raised above and below; tertiaries faint, reticulate; intramarginal veins c. 0.5 mm from margin, straight; petiole (1-) 2.5-6 mm long, 1/6-1/15 of blade length, c. 1 mm diameter, slender or stout, brownish, not contrasting to blade colour. Inflorescence terminal, to 2 cm long, racemose or first order branching, flowers 3 to 17; axes 0.5-0.8 cm long; bracts and bracteoles caducous, not seen. Flower white (in vivo), sessile or pedicellate, pedicel 1-2 mm, hypanthium not glaucous, not fibrous, (5.5-)7-8 × (4-) 5-6 mm, pyriform, pseudostalk distinct, 3-3.5 mm long; sepals 4, free, 3 × 5 mm, semiorbicular; petals 4, free, 6-7 × 6-7 mm, semiorbicular; outer stamens c. 1 cm long, anther sacs parallel, connective gland conspicuous; style c. 11 mm long, ovules c. 4 per locule, irregularly radiating. Fruit not seen.

REMARKS

The specimen collected at 1500 m elevation (Poilane 3781) displays smaller and narrower leaves (2.5-3.4 × 0.7-1.2 cm, 3 to 3.5 times as long as wide) and shorter petiole (1-2.5 mm long) than lowland specimen (Poilane 6237) which has larger and broader leaves (2.5-5 × 1.5-2.5 cm, 1.5 to 2 times as long as wide) and longer petiole (4-6 mm long). It is often the case that plants collected in the mountains along ridges are found in exposed habitats and therefore their leaves frequently reflect extreme environmental conditions in such features as the recurved leaf margin, reduced foliage, coriaceous leaf texture, and reduced petiole ( Van Steenis 1948).

Figures

FIG. 2. — Syzygium samianum W.K. Soh & J.Parn., sp. nov.: A, flowering branch; B, flower bud; C, longitudinal section of mature flower; D, leaf venation. Poilane 6237. Scale bars: A, 1 cm; B, C, 5 mm; D, 2 mm. Drawn by Wuu Kuang Soh.