Hoya danumensis subsp. amarii S.Rahayu & Rodda, 2019

Rahayu, Sri & Rodda, Michele, 2019, Hoya of Sumatra, an updated checklist, three new species, and a new subspecies, European Journal of Taxonomy 508, pp. 1-23 : 4-7

Hoya danumensis subsp. amarii S.Rahayu & Rodda subsp. nov.

urn:lsid:ipni.org:names:77194999-1

Figs 1 A–B, 2A–B

Etymology

The new species is named after Amar Husein Sitompul, who collected the type specimen.

Type material

Holotype INDONESIA • Sumatra, North Sumatra, Padang Sidempuan ; ca 900 m a.s.l.; 16 Sep. 2014; Amar Husein Sitompul s.n. leg.; BO.

Description

Epiphytic shrub, with white latex in all vegetative parts. Roots only basal, no adventitious roots observed. Stems erect or spreading, 4–6 mm in diameter, bright green, sparsely pubescent when young; older stems grey, glabrous; internodes 2–4(6) cm. Leaf blades 5–12 × 2.5–5 cm, thin, not succulent, chartaceous when dry, broadly lanceolate to oblong, base rounded, apex acuminate or caudate, mid green on adaxial surface, pale green on abaxial surface, glabrous (sparsely pubescent when young), venation pinnate, midrib slightly depressed on adaxial surface, convex on abaxial surface, secondary veins 3–7 pairs, basal colleters absent; petioles 5–10 × 2–3 mm, terete, channelled above, twisted, mid green, sparsely pubescent when young, otherwise glabrous. Inflorescences sciadioidal, convex, of 5–15 flowers, with peduncles extra-axillary, positively geotropic, unbranched, one at each node, producing flowers subsequently a few times, terete, 10–15 × 1.5–2.5 mm, green, sparsely pubescent when very young. Flowers with terete pedicels 2.5–3 cm × 0.06–0.08 mm, pale green, glabrous. Calyx lobes triangular, apex round, 1.5–2 × 0.5–0.6 mm, sparsely pubescent outside or glabrous, inside glabrous, ciliate; basal colleters 0.15–0.25 × 0.15–0.2 mm, one at each calyx sinus, ovoid. Buds globose, 5-ridged, dark brown or deep purple when young, turning green. Corolla shallowly campanulate, 20–23 mm in diameter; tube 9–11 mm long, creamy white, glabrous outside, pilose inside, basally densely pubescent; lobes 2–3 × 11–12 mm, very broadly triangular, valvate in bud, creamy white, glabrous outside, very sparsely pubescent inside, tip glabrous. Corona staminal 4–5 mm high, 10–12 mm in diameter, stiff and waxy-looking, white; lobes 4.5–5 × 2.3–2.5 mm, spreading, ovate, attached at the back of the anthers, inner process apiculate, not touching in the middle, outer process acute with a rounded tip, lobes with revolute margin underneath. Anthers ca 0.7 × 0.5 mm, ovate, with apical round membranaceous appendage covering the style-head apex. Pollinia 550–650 × 220–270 μm, oblong, with a round base and an obliquely truncated apex; pellucid margin present all along the outer edge; caudicles ca 280 × 180 μm, broadly triangular, almost transparent; corpusculum 300–350 × 100–120 μm, oblong; style-head 5-angled in cross section, with five spreading lobes alternating with the stamens, style-head depressed with a central raised conical apex ca 0.5 × 0.5 mm broad at the base, apex rounded; ovary 1.4–1.6 mm high, 0.3–0.4 mm in diameter, narrowly conical, apex acute. Fruit and seed not observed.

Distribution and habitat

Hoya danumensis subsp. amarii subsp. nov. is only known from the type locality in northern Sumatra, Indonesia, ca 900 m a.s.l.

Conservation status

Known only from a single collection and lacking information on the distribution area, the population size and the possible threats to the habitat, H. danumensis subsp. amarii is considered as Data Deficient (DD) ( IUCN 2012).

Notes

Hoya danumensis subsp. amarii subsp. nov. can be separated from H. danumensis Rodda & Nyhuus (2009) subsp. danumensis because of the shape and size of the corolla that is shallowly campanulate, 20–23 mm in diameter and deeply campanulate, vs 25–35 mm in the latter; in the shape and size of the corona lobes that are ovate-oblong and 5.5–6 × 2.4–2.6 mm in H. danumensis subsp. danumensis vs ovate and 4.5–5 × 2.3–2.5 mm in the new subspecies.

Figures

Fig. 1. Flowers. A, C, E. Top view of the flower. B, D, F. Side view of the flower, with part of corolla removed. A–B. H. danumensis subsp. amarii S.Rahayu & Rodda subsp. nov. (Amar Husein Sitompul s.n. leg., BO). C–D. H. solokensis S.Rahayu & Rodda sp. nov. (Fadly s.n. leg., BO). E–F. H. rigidifolia S.Rahayu & Rodda sp. nov. (S. Rahayu 865 leg., BO). Drawing: X. Y. Loh.