Hoya sumatrana Rahayu & Rodda 2019, sp. nov.
Creators: name: Rahayu, Sri
name: Rodda, Michele
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Apocynaceae
Hoya
Hoya sumatrana

description: Hoya sumatrana S.Rahayu & Rodda sp. nov.
urn:lsid:ipni.org:names:77195002-1
Figs 3–4
Etymology
The new species is named after the Indonesian island of Sumatra.
Type material
Holotype INDONESIA • Sumatra, Lampung, Taman Nasional Bukit Barisan Selatan, Tambling; 20 Sep. 2013; S. Rahayu 861 leg.; lowland forests; BO.
Isotype INDONESIA • Same data as for the holotype; SING.
Description
Epiphytic climber, with white or yellowish latex in all vegetative parts. Roots adventitious below the nodes and along the internodes. Stems 2–4 mm in diameter, climbing, dull green, pubescent; older stems grey, glabrescent; internodes 2–5(10) cm. Leaf blades 3–7(15) × 3.5–5.5 cm, stiff and succulent, oblong, ovate or elliptic, base round to attenuate, apex acute, mid green on adaxial surface with sparse grey spots, pale green on abaxial surface, glabrous, or very sparsely pubescent when young, venation pinnate, inconspicuous, basal colleter ca 1 × 1.5 mm, one at each lamina base, broadly triangular, pale brown; petioles 10–20 × 3–6 mm, terete, dark brown, sparsely pubescent when young. Inflorescences 2.5–3 cm in diameter, of 10–15 flowers, sciadioidal, flat; peduncles 15–35 × 1.5–2 mm, extra-axillary, positively geotropic, 1 at each node, producing flowers over an extended period of time, terete, dark red, sparsely pubescent. Flowers with terete pedicels 5–15 × 0.7–1 mm, dark red at the base, fading to pale pink towards the calyx, sparsely papillose. Calyx lobes narrowly triangular, spaced 0.6–0.8 mm apart, apex acute or rounded, 1.4–2 × 0.5–0.8 mm, reddish, papillose outside, inside glabrous, sparsely ciliate; basal colleters 0.16–0.18 × 0.09–0.11 mm, one at each calyx sinus, ovoid. Corolla 7–9 mm in diameter when flattened, rotate; tube ca 1.5 mm long, cream, glabrous outside, densely pubescent inside; lobes triangular, valvate in bud, with recurved edges and revolute tip, 5–6 × 2–3 mm, glabrous outside, densely pubescent inside with a glabrous tip ca 1.5 mm long. Corona staminal 2–2.5 mm high, 2.8–3.2 mm in diameter, red; lobes ca 2.2 × 0.8 mm, attached at the back of the anthers, held at ca 60° angle, ovoid, slightly carinate above, inner process bilobed, outer process rounded, with a narrow basal revolute margin. Anthers ca 0.5 × 0.4 mm, ovate, with a linear apical round membranaceous appendage to 2.8 mm long. Pollinia 280–320 × 100–120 μm, oblong, with a round base and obliquely truncate; pellucid margin all along the outer edge; caudicles 100–120 × 70 μm, broad, almost transparent; corpusculum 90–110 × 40–60 μm, oblong; style-head 5-angled in cross section, with five spreading lobes alternating with the stamens, style-head apex 0.8–0.9 mm long, 0.4–0.5 mm broad at the base, conical, with apex acute; ovary 1.5–2 × ca 0.5 mm at the base, conical, with apex acute. Fruit and seed not observed.
Distribution and habitat
Hoya sumatrana sp. nov. is only known from the type locality in in Lampung, Sumatra, Indonesia. It was collected in a coastal swamp forest, where it was growing as an epiphyte.
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. sumatrana sp. nov. is considered as Data Deficient (DD) (IUCN 2012).
Notes
Hoya sumatrana sp. nov. is a new species in H. sect. Peltostemma Schlechter (1916: 14), characterized by upright corona lobes, long linear anther appendages extending well above the style-head and pollinaria with well developed caudicle wings. This section includes six species, two of which, H. soidaoensis Kidyoo (2013) and H. phuwuaensis Kidyoo (2016), have been recently published. Hoya sumatrana sp. nov. can be separated from all other members of this section because its flowers are much smaller; for example, the corolla of H. sumatrana sp. nov. is 7–9 mm in diameter, while the corolla of the second smallest species, H. flagellata Kerr (1940: tab. 3407), is> 10 mm in diameter, as well as the corona of Hoya sumatrana sp. nov. is 2.8–3.2 mm in diameter, while that of H. flagellata is> 4 mm in diameter. Another useful character to separate H. sumatrana sp. nov. from all other members of the section is the inner corona lobe process, that is bilobed in H. sumatrana sp. nov., while the other species have acute or rounded processes.
description: Published as part of Rahayu, Sri & Rodda, Michele, 2019, Hoya of Sumatra, an updated checklist, three new species, and a new subspecies, pp. 1-23 in European Journal of Taxonomy 508 on pages 15-18, DOI: 10.5852/ejt.2019.508, http://zenodo.org/record/2612875