Syzygium sirindhorniae Chantar., Suksathan & M.Wongnak, 2016

Chantaranothai, Pranom, Suksathan, Piyakaset & Wongnak, Methee, 2016, Syzygium sirindhorniae (Myrtaceae), a new species from Thailand, Phytotaxa 289 (2), pp. 193-196 : 193-195

Syzygium sirindhorniae Chantar., Suksathan & M.Wongnak , sp. nov., Figures 1 – 2

Syzygium sirindhorniae is similar to S. bokoense Soh & Parnell (2011: 557) in having strongly cordate leaf base but differs in having larger habit and leaves, blades with fewer lateral veins and no intramarginal vein and terminal inflorescences with larger flowers.

Type:— THAILAND. Chiang Mai, Fang district: Doi Fah Hom Pok , Sanju , 1,700 m elev., along cliff and steep slope in open pine-oak forest, 25 December 2009, P. Suksathan 4925 (holotype QBG!; isotypes BKF!, KKU!) .

Shrub or small tree 3–5 m tall; bark brownish; branchlets terete, smooth. Petiole 0.5–1 mm long, the leaves appearing sessile. Leaves strongly opposite decussate, thickly coriaceous, stiff; blades, 8–12 × 5–7 cm, ovate, ovate lanceolate or ovate elliptic, base cordate, apex acute, margin revolute; midrib on the upper surface flat near the top but raised with a furrowed central channel from middle to the base of leaf, prominent and semi-terete on the lower surface; lateral veins 11–12 pairs, widely spaced, 8–13 mm apart, raised above; intramarginal veins absent; tertiary venation slightly prominent, raised above. Inflorescence up to 4 cm long; peduncle up to 3 mm long, rachis and branches stout, terete. Flowers white, sessile; bracts 3 × 1 mm, caducous; bracteoles 1 × 1 mm, triangular, caducous. Hypanthium 8–10 × 8–10 mm, funnel-shaped, ridged, creamy white. Pseudostalk 2–3 mm long. Calyx lobes 4, 4–5 × 1.5–3 mm, semi-orbicular, rim hyaline, slightly persistent, purplish red. Petal s 4, free, 7–7.5 × 8–10 mm, orbicular, membranous, with 30–50 dots per petal, creamy white, pale green at the base. Outer stamens white with pale pink at base, 2.8–3.5 cm long; inner stamens 1.5–2 cm long, white to creamy white; anther pale yellow, 1–1.2 mm long, linear oblong or ovate oblong. Style 2.3–2.5 cm stout. Ovary 2-locular, 18–20 ovules per locule. Fruits up to 3 cm in diameter, sub-globose, purplish green when mature, calyx ring with persistent sepal lobes. Seeds 4, 2–2.5 cm long, quarter spherical.

Distribution and ecology: —Endemic to Thailand and known only from the type locality in Chiang Mai. The species is scattered on vertical cliffs in open pine-oak forest at 1,600 –1,700 m elev.

Phenology: —Flowering between December–March. Fruiting between May–June.

Etymology: —The specific epithet is given in honour of Her Royal Highness Princess Maha Chakri Sirindhorn of Thailand who has long been interested in botanical diversity. She has initiated the Plant Genetic Conservation Project under The Royal Initiative of H.R.H. Princess Maha Chakri Sirindhorn.

Vernacular name: —Rat-cha-rat (name given by H.R.H. Princess Maha Chakri Sirindhorn).

Paratype: — THAILAND. Chiang Mai, Doi Fah Hom Pok (Mae Fang), 1,600 m elev., on rocky cliff, 16 February 2006, C. Maknoi 652 (QBG 25612!).

IUCN Conservation status: —This species has been collected twice but only from Doi Fah Hom Pok, Chiang Mai, presently the species is known from only about 20 individuals in the collection site. The habitat is a protected area and therefore the species does not strictly qualify for any of the IUCN threatened categories ( IUCN 2012), and is this provisionally assessed as Near Threatened (NT). Living plants now are grown in highland area of Queen Sirikit Botanic Garden, Chiang Mai.

Note: —The general aspect of Syzygium sirindhorniae is similar to S. bokoense , a Cambodian species but differs in having larger leaves and flowers, fewer lateral veins without intramarginal vein (see comparison of the species in Table 1).

Figures

FIGURE 1. Syzygium sirindhorniae: A. Habit; B. A portion of lower surface of leaf base; C. Flower; D. Sepal; E. Petal; F. Portion of stamens; G. Longitudinal section of ovary, showing two locules; H–I Fruit (A–I from P. Suksathan 4925; drawn by W. Thammarong).

FIGURE 2. Syzygium sirindhorniae: A. & B. Habit & habitat; C. Inflorescences; D. Fruits (Photos taken by P. Suksathan).