Hoya solokensis 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 : 14-15

Hoya solokensis S.Rahayu & Rodda sp. nov.

urn:lsid:ipni.org:names:77195001-1

Figs 1 C–D, 2C–D

Etymology

The new species is named after the collection locality in Solok, Sumatra.

Holotype

INDONESIA • Sumatra, Solok ; ca 1000 m a.s.l.; 10 Oct. 2016; Fadly 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, 2.5–5 mm in diameter, dull green, sparsely pubescent when young; older stems grey-brown, glabrous; internodes 1–2(5) cm. Leaf blades 5–10(12) × 2.5–4 cm, thin, not succulent, chartaceous when dry, elliptic, base and apex acute or acuminate, mid green on adaxial surface, pale green on abaxial surface, glabrous, venation pinnate, midrib slightly depressed on adaxial surface, convex on abaxial surface, with 4–7 pairs of secondary veins, basal colleters absent; petioles 5–10 × 1.7–2 mm, terete channeled above, mid green, sparsely pubescent. Inflorescences sciadioidal, convex, of 3–10 flowers; peduncles 8–12 × 1.2–1.4 mm, extra-axillary, positively geotropic or horizontal, unbranched, one at each node, producing flowers only once, terete, green, sparsely pubescent just below the rachis, otherwise glabrous. Flowers with terete pedicels 5–8 × 1–1.5 mm, pale green, sparsely pubescent. Calyx lobes ovate- round, apex round, 1.4–2.2 × 1.2–1.6 mm, light green, pubescent outside, glabrous inside, ciliate; basal colleters 1.5–2.3 × 1.3–1.5 mm, 1–3 at each calyx sinus, ovoid. Corolla tube basally bulbous, tightly enveloping the lower half of the corona, with a contracted throat, a short funnel-shaped tube and free, lanceolate, spreading lobes, white; basal bulbous part 2.5–3 mm high, 3–3.5 mm in diameter; free lobes 5–6 × 2.5–3 mm, narrowly triangular, valvate in bud, with recurved edges and tip, tube pubescent inside with retrorse hairs, sparsely pubescent outside with spreading hairs, lobes sparsely pubescent inside and outside with spreading hairs. Corona staminal 4.5–5 mm high, 2.5– 3 mm in diameter, stiff and waxy-looking, white; lobes 4.5–5 × 1–1.2 mm, erect, oblong and sinuose, attached at the back of the anthers, upper apicis rounded, touching in the middle, outer tips obtuse, with a narrow revolute margin.Anthers ca 0.5 × 0.3 mm, ovate, with apical round membranaceous appendage just covering the style-head apex. Pollinia 470–520 × 200–240 μm, oblong, with a round base and apex; pellucid margin missing; caudicles ca 130 × 70 μm, ovoid, almost transparent; corpusculum 300–320 × 160–180 μm, ovoid; style-head 5-angled in cross section, with five spreading lobes alternating with the stamens, style-head apex conical, 1–1.2 mm high, 0.9–1.1 mm in diameter at the base, apex acute; ovary 1.5–1.7 mm high, conical, with apex acute. Fruit and seed not observed.

Distribution and habitat

Hoya solokensis sp. nov. is only known from the type locality in Solok, Sumatra, Indonesia, at ca 1000 m a.s.l. It was collected in an evergreen forest, where it was growing epiphytically.

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. solokensis sp. nov. is considered as Data Deficient (DD) ( IUCN 2012).

Notes

Hoya solokensis sp. nov. is one of the few species of Hoya that exhibits a non-climbing habit but is instead an epiphytic shrub. It is morphologically similar to H. papaschonii Rodda (Rodda & Ercole 2014) , a species only found in southern Thailand. Both species share a shrubby habit, short-lived peduncles, and flowers with a tubular corolla. However, H. papaschonii has the free part of the corolla lobes mostly held upright, while in H. solokensis sp. nov. the lobes are spreading; furthermore, the corona of H. papaschonii has both staminal and interstaminal elements while H. solokensis sp. nov. only has a staminal corona. Another species with a tubular corolla is H. telosmoides Omlor (1996) from Borneo, that is, however, a climber. The flowers of H. solokensis sp. nov. superficially resemble those of the Bornean H. hamiltoniorum A.L. Lamb, Gavrus, Emoi & Gokusing (Lamb et al. 2014) because both species have the free part of the corolla lobes spreading, however H. hamiltoniorum is a climber and its inner apex of the corona lobe is bifid, while the apex of the inner lobes of H. solokensis sp. nov. is entire.

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.