Friday, February 16, 2018

[Botany • 2018] Hoya phuluangensis • A New Species of Hoya (Marsdenieae), Three New Combinations and Two New Names in Vincetoxicum (Asclepiadeae) from Thailand

Hoya phuluangensis  Kidyoo  
in Kidyoo & Kidyoo, 2018. 

Hoya phuluangensis Kidyoo, a new species from northeastern Thailand is here described and compared to the similar species, H. rostellata and H. siamica. All three species have glabrous stems and branches, glabrous coriaceous leaves, adaxially puberulent ovate corolla lobes with an acute apex, and flat to slightly erect coronal scales with an obtuse or rounded apex. However, H. phuluangensis differs from the other two species in the following characters: flowers with a shallow cup-shaped corolla tube and a corona diameter measuring less than half of the corolla tube diameter. Full description of H. phuluangensis is provided, together with line drawings and photographs. In addition, three new combinations and two new names in the genus Vincetoxicum, namely V. indicum (Burm.f.) Mabb. var. glabrum (Decne.) A. Kidyoo, V. kerrii (Craib) A. Kidyoo, V. sootepense (Craib) A. Kidyoo, V. lindleyi A. Kidyoo and V. potamophilum A. Kidyoo, are proposed.

Keyword: Apocynaceae, Asclepiadoideae, Hill evergreen, Hoya phuluangensis, Thailand, Vincetoxicum

Fig. 2. Photographs of Hoya phuluangensis Kidyoo.
 A: Habitat. B: Flowering branch. C: Inflorescence. D: Flower, top view. E. Flower, side view.
All photographs by M. Kidyoo.

Hoya phuluangensis is distinguished from H. rostellata by a flower with corolla lobes not reflexed when in full bloom and with slightly revolute margins, shallow cup-shaped corolla tube, and corona diameter less than half of the corolla tube diameter. In contrast, H. rostellata has corolla lobes with strongly revolute margins and apex, corolla tube spreading in a flat form, and corona of diameter more than half of the corolla tube diameter.

Ecology and distribution: This plant usually grows in shady areas in hill evergreen forest from 1,400 m a.s.l., climbing on tree trunks and branches.  

 Etymology: The specific epithet of the new species is derived from ‘Phu Luang Wildlife Sanctuary’, the place where it was first discovered. 

Fig. 3. Comparison between A & D: Hoya phuluangensis Kidyoo, B & E: H. rostellata Kidyoo, and C & F: H. siamica Craib. A – C: Flower, D – F: Leaf.
All photographs by M. Kidyoo.

Aroonrat Kidyoo and Manit Kidyoo. 2018. A New Species of Hoya (Marsdenieae), Three New Combinations and Two New Names in Vincetoxicum (Asclepiadeae) from Thailand. Taiwania. 63(1); 25-31.  DOI:  10.6165/tai.2018.63.25

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