THAI FOR. BULL. (BOT.) 36: 81–85. 2008.
Hoya imperialis Lindl. (Apocynaceae:Asclepiadoideae), a new record for Thailand
JAREARNSAK SAE WAI*, KITICHATE SRIDITH* & OBCHANT THAITHONG**
ABSTRACT. Hoya imperialis Lindl. is newly recorded for Thailand from Betong district in Yala province. The species is described and illustrated.
KEYWORDS: Hoya, Asclepiadoideae, Apocynaceae, new record, Yala province.
The Genus Hoya R.Br. (Apocynaceae: Asclepiadoideae) comprises approximately at least 200 species (Wanntorp et al., 2006). It is distributed inAsia andAustralasia (Hooker, 1883; Ridley, 1923; Li et al., 1995). Kerr (1951) recognised 24 species of Hoya in Thailand. Recently, during a survey on some isolated rocky mountains along Thai-Malaysian border, many Malesian elements were collected. One of them is Hoya imperialis Lindl., which is a new record for Thailand.
Hoya imperialis Lindl. has one of the largest flowers of all species in the genus Hoya. It has been, in fact, well known in the trade name Hoya “Chakra Bhad” (meaning “Emperor Hoya” -Authors). Introduced plants from Borneo have been cultivated as ornamental plants in Thailand for some years. The species was previously recorded from mangrove and lowland forests in Johore, Melaka, Perak, Selangor and Borneo (Rintz, 1978). Until the discovery of this species in southern Thailand, the Perak region in the north of Malaysia was the northernmost limit of wild populations of this species.
Hoya imperialis Lindl., Bot. Reg. sub t. 68. 1846; Hook.f., Fl. Brit. India 4: 59. 1883; Ridl., Fl. Malay Penins. 2: 399. 1967; Rintz, Malay. Nat. J. 30 (3–4): 501, 503. Fig. 18. 1978. Figs. 1–2.
Climber, stem scandent, 0.5–1.5 cm in diam., pubescent, internodes 5–25 cm long; latex white. Leaves coriaceous, rigid, thick and fleshy; petioles 1–1.5 cm long, diameter 2– 2.5 mm, pubescent; blades obovate-lanceolate to oblong, elliptic or oblanceolate, 5–15 by 2–5 cm, glabrous on both surfaces, upper surface shining, apex short acuminate and usually reflexed, base rounded or acute, margin entire or undulate, slightly recurved, ciliated; midrib channelled above when dry, prominent underneath, ciliated on both surfaces, secondary
Herbarium (PSU), Centre for Biodiversity of Peninsular Thailand (CBIPT), Department of Biology,
Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand. ** Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.