Hoya wongii Rodda, Simonsson & L.Wanntorp, 2011

Hoya wongii Rodda, Simonsson & L.Wanntorp View in CoL , sp. nov. — Fig. 1 View Fig , 2

Ad Hoyam campanulatam Blume similis ob corollam campanulatam, sed differt coronae lobis inferius inflatis et superne erectis, compressis cum binis appendicibus membranaceis bidentatis. — Typus: K. M. Wong ( KMW) 1566 (holo BRUN; iso K, L, SAN, SING), Borneo, Brunei, Tutong district, Pasir Puteh , 5 Oct. 1989 .

Etymology. Hoya wongii is named after its first collector Dr. Wong Khoon

Meng, who has greatly contributed to the knowledge of the SE Asian flora.

All measurements from rehydrated material.

Semi-woody, slender glabrous vine with white latex. Leafy stems cylindrical 2.5 –3 mm diam, older stems leafless, bark waxy, peeling at least on dry material. Internodes 15–150 mm, adventitious roots absent. Leaves opposite, petiolate; petiole 3 –7 by 0.7–1.2 mm; lamina coriaceous, flexible, not succulent, elliptic, 50– 90 by 20– 40 mm, widest in the central portion, apex apiculate-cuspidate, base shortly attenuate, margin entire, penninerved, main vein depressed on adaxial surface, evident on abaxial surface, secondary veins 5–7 pairs evident when dry, anastomosing near leaf margins. Inflorescences pseudo-umbelliform, 1-flowered; peduncle extra-axillary, perennial, about 10 mm long, pedicels 15– 25 by 0.4 –1 mm, glabrous. Calyx c. 5 mm diam, sepals oblong, about 2 by 1.6 mm, apex rounded, margins ciliate. Corolla campanulate, pale yellow, 25– 30 mm diam; corolla lobe fused for c. 18 by 16 mm, free lobes c. 5 mm long with acute tips. Corona staminal pale yellow, 5– 6 mm high, 6 mm diam, outer processes broadened into a rounded free process with revolute lateral margins, inner processes laterally compressed, ending in two bidentate membranaceous appendages, about 2 mm higher than outer processes and 0.3 mm higher than inner processes; anther skirt revolute, free from the filament tube. Guide rail forming a ridge, laterally compressed, prominent at the base of the anther skirt and extending 0.3 –0.5 mm laterally. Pollinarium c. 1 mm long, pollinia oblanceolate, 830 by 300 μm, apex rounded to obtuse, retinaculum 280 by 180 μm, caudicles 120 μm long. Ovary rounded, 2.5 mm long. Fruits and seeds not seen.

Distribution — Brunei, possibly other areas of Borneo.

© 2011 Nationaal Herbarium Nederland

1 mm 1 mm

Habitat & Ecology — A climbing epiphyte only found in the type locality. The type locality is in a coastal kerangas heath forest with white sand, 15– 30 m above sea level .

Additional specimens seen. Hoya campanulata Blume sin.coll., L 0004389 (type L), Java, Ex Hort Bogor. Hoya collettii (Collett & Hemsl.) Schltr., Collett 833 (type K), Myanmar, Shan Hills, 6000 ft, June 1888. Hoya manipurensis Deb, Micholitz s.n. ( holotype of Micholitzia obcordata N.E.Br., K ), ‘ India & Burma’, cult. Royal Bot. Gard. Glasnevin, Dublin, 1909. Hoya danumensis Rodda & Nyhuus, M. Rodda 2008.1h ( holotype FI) ex hort., 3 Sept. 2008. Hoya phyllura O.Schwartz, Winkler 339 (type HBG), Lebang Hara, West Borneo, 24 Nov. 1924. Hoya telosmoides Omlor , Clemens 29828 ( holotype BM), Malaysia, Sabah, Mt Kinabalu, Tenompok, 1500 m, 7 June 1932. Hoya vacciniiflora O.Schwartz, Winkler 518 (type HBG), Bukit Mulu, West Borneo, 2 Dec. 1924.

Conservation status — Hoya wongii should be considered

Data Deficient ( DD) according to IUCN Red List criteria ( IUCN

Fig 2 Hoya wongii Rodda, Simonsson & L.Wanntorp. The peculiar single-flowered inflorescences are evident on this specimen ( holotype in BRUN herbarium). Photo by Dr. Jacqueline Henrot, BRUN.

2001) because it is known from only one collection and thus remains in need of further investigation with respect to future conservation efforts. This species was found in kerangas heath forest, a nutrient poor habitat rarely used for cultivation. However, felling and burning activities may degrade kerangas into an open savanna of shrubs ( Whitmore 1984) making it inhospitable for many epiphytic plant species including Hoya .

Notes — Due to its broadly campanulate corolla, specimens of H. wongii can be easily confused with specimens of H. campanulata , H. danumensis , H. nyhuusiae , H. phyllura or H. vacciniiflora . However, none of these species have coronas showing the same morphological characters as in H. wongii . Here, the corona has broadly inflated outer processes and laterally compressed inner processes with two bidentate membranaceous appendages. All other Bornean species of Hoya with a campanulate or semi-campanulate corolla have spreading elongated corona lobes and a well-developed anther skirt forming a disk at the base of the corona. Among species with a campanulate to semi-campanulate corolla, H. collettii , resembles H. wongii in the morphology of the corona. This species, which is endemic to Myanmar, is so far only known from the type specimen. It differs from H. wongii in being a small shrub with very thick, narrowly lanceolate leaves and not a vine with thin, elliptic leaves. Further, H. collettii has rounded outer corona processes much less developed than those of H. wongii . The outer corona processes are very elongated but not laterally compressed and lack the two bidentate appendages of H. wongii .

Two additional species of Hoya , one again endemic to Borneo and the other found in India, Thailand and China, show a slightly similar corona to that of the new species. The first, H. telosmoides ( Omlor 1996) , from Borneo, has only been collected from Mt Kinabalu, to which it is possibly restricted. The corolla in H. telosmoides is not campanulate as that of H. wongii but urceolate and hairy on the inside. These two species have similar coronas, with well-developed erect outer processes. The inner coronal processes of H. telosmoides are, however, much less developed than those of H. wongii and lack the bidentate appendages. The second species, H. manipurensis ( Deb 1955) , is a species growing at low to middle altitudes in cool sub-tropical zones of India, China and Thailand. It also has an urceolate corona similar to that of H. telosmoides . In addition, H. manipurensis also differs in habit, being an epiphytic shrub and not a vine, and in having c. 10 mm long greenish red tubular flowers instead of pale yellow campanulate flowers.