Sunday, August 3, 2014

[Botany • 2014] Hoya papaschonii • A New Species (Apocynaceae: Asclepiadoideae) from southern Thailand with A Peculiar Corona

FIGURE 4. Photographs of a living plant of Hoya papaschonii Rodda
cultivated at the Singapore Botanic Gardens (acc. no. 20132440):
a. Flowering branch and paired fruits; b. Bud; c. Flower, lateral view; d. Flower with two corolla lobes removed, showing the position of the corona basally enveloped by the corolla lobes; e. Flower, longitudinal section; i. Corona, lateral view; j. Corona, top view; k. Flower, longitudinal section with the position of the guide rail highlighted in black; l. Anther and anther appendages (after removal of one staminal corona lobe).
Photographs by M. Rodda. The parts of the gynostegium are labelled as: A = Anther; Aa = Anther appendage; C(is) = interstaminal corona lobe; Cs = Staminal corona lobe; G = Guide rail; Re = Retinaculum; S = Stigma; Sh = Stigma head.

The new Hoya species, here described and fully illustrated, is an epiphytic shrub with white-cream coloured flowers superficially similar to those of Hoya telosmoides. Its gynostegial corona includes five staminal and five interstaminal lobes, the latter never before observed in Hoya. The placement of the new species within Hoya was confirmed by a phylogenetic analysis based on nuclear ribosomal ITS and 5’-ETS regions, and chloroplast psbA-trnH and trnT-trnL intergenic spacers. It belongs to a group of species including Hoya multiflora and Hoya praetorii, characterised together with H. papaschonii by non-climbing habit, thin leaves lacking basal colleters, and short-lived peduncles.
Keywords: Hoya sect. Centrostemma, Hoya sect. Cystidianthus, Hoya sect. Plocostemma, ITS, 5’-ETS, psbA-trnH, trnT-trnL 

Hoya papaschonii Rodda

Similar in habit to Hoya multiflora, and in corolla morphology to Hoya telosmoides but the gynostegial corona presents a unique combination of both staminal and interstaminal lobes.
Type:—THAILAND. Original collection in Yala: Betong, cultivated in Thailand, Ratchaburi Province, Ratchaburi, November 2012, Papaschon Chamwomg KEW2012-011 (holotype BKF, isotypes BCU, K, SING).

Etymology:— The new species is named after the collector and Hoya enthusiast Mr. Papaschon Chamwong who, in 2012, sent a specimen of the new species to Singapore Botanic Gardens for identification.

Distribution and ecology:— Hoya papaschonii is only known from two collections in Betong District, Yala Province in southern Thailand. It was collected in evergreen forest, where it was growing epiphytically. 

Conservation status:— Known only from two collections from Yala Province in Thailand. The distribution area, the population size and the possible threats to the habitat are unknown. We therefore consider H. papaschonii as Data Deficient (DD) (IUCN 2014).

Michele Rodda and Enrico Ercole. 2014. Hoya papaschonii (Apocynaceae: Asclepiadoideae), A New Species from southern Thailand with A Peculiar Corona. Phytotaxa. 175(2): 097–106.