Hoya liddleana Simonsson & Rodda, 2022

Hoya liddleana Simonsson & Rodda View in CoL , sp. nov. — Fig. 7 View Fig , 8 View Fig

Similar to Hoya onychoides P.I.Forst., Liddle & I.M.Liddle in flower size (c. 5 cm diam in natural state), corolla shape, with inflexed ‘claw-like’ lobes and with oblong corona lobes, but differs in corolla pubescence (thinly pubescent inside in H. liddleana vs glabrous or occasionally only sparsely pubescent in H. onychoides ), and corona shape (inner part conical, outer part spreading in H. liddleana vs entirely conical in H. onychoides ). — Type: N. Simonsson & T. Nyhuus NS 0116 L (holo SING), Papua New Guinea,Milne Bay Province, Alotau, trail towards Gamopupu waterfall, 20 m, in lowland disturbed primary forest,living accession NS08 –100, vouchered in cultivation in Stockholm, Sweden, on 26 Mar. 2016 .

Etymology. Named after David and Iris Marie Liddle of Mareeba, Australia. David Liddle (–2009) was a keen plant collector, grower and amateur scientist.He described 15 new taxa together with Paul I. Forster ( IPNI 2021) and ran a plant nursery with Iris Marie containing a large selection of Hoya species.

Epiphytic climber with white latex in all vegetative parts. Stems up to 10 m long, cylindrical, 2 –10 mm diam, green to greyish brown, glabrescent; older stems leafless and lignified, up to 15 mm diam, internodes 3–30 cm long. Adventitious roots numerous, scattered along the stems. Leaves: petiole 15– 50 by 3–7 mm, green to brown, glabrous (sometimes sparsely pubescent when young); lamina pendulous, lanceolate, very succulent and fleshy, 7–20 by 2–10 cm, up to 5 mm thick, dark green on adaxial surface, medium green on abaxial surface, glabrous, apex acute, base cordate; venation pinnate, midrib depressed on adaxial surface, secondary veins 4–7 each side, anastomosing in the middle between midrib and leaf margin or closer to the leaf margin. Inflorescence one per node, positively geotropic, pseudo-umbelliform, convex, consisting of 3–12 flowers; peduncle extra-axillary, terete, 2 –7 cm by 2 – 5 mm, grey-brown, older peduncles forming a rachis from previous flowerings, glabrous; pedicels terete, 5 –7 cm by c. 2 mm, light green, glabrescent. Calyx 10–12 mm diam; lobes triangular-ovate, 3.5–5 by 3.5–4.5 mm, apex rounded. Corolla rotate with inflexed ‘claw-like’ lobes, c. 5 cm diam in natural state (to 7 cm when flattened), deep pink to wine-red with whitish centre beneath the corona; tube 1.2–2.5 cm long, outside glabrous, inside pubescent with thin hairs, glabrescent towards the centre; lobes fleshy, triangular-acuminate, 2 – 3 by 1.5–2.5 cm, margin c. 5 mm reflexed to revolute, apex acute, outside glabrous, inside pubescent with thin hairs. Corona staminal, c. 1.5 cm high, 2–2.8 cm diam, fleshy, cream, with a pink or maroon centre, inner part conical, c. 1.5 cm across, outer part spreading; lobes oblong, centrally ridged, 1.4–1.8 by 0.3–0.4 cm, inner process 6–8 by 4–6 mm, apex acuminate, meeting in centre, outer processes oblong, laterally concave, 1–1.3 cm long, 4–6 mm high, tip apically slightly raised, basally bilobed, with basal margins becoming revolute and touching each other only towards the apex of the outer corona lobe. Pollinia oblong, c. 1300 by 400–450 µm, with pellucid margin; corpusculum rhomboid with slight constriction in the middle, 600–700 by c. 400 µm; caudicles attached to the middle of the corpusculum, c. 200 by 150 µm. Ovary conical, c. 4 mm long, glabrous. Fruit and seed not observed.

Distribution — This species is known from the easternmost part of the Milne Bay Province of Papua New Guinea only. It is available in the horticulture trade as collection numbers SV416 and SV441, collected by Arne Kastberg ( Sweden), from Tawali, also in eastern Milne Bay province.

Habitat & Ecology — A climber on trees in coastal or riverine forests, in bright or sunny habitats. Locally common in some of the forest remnants. It was also sighted on a Ficus sp. tree in a garden near Alotau town.

Conservation status — Critically endangered CRB1a,b(iii) (CR; IUCN 2012). This species appears to be common at the type locality, but it may be locally endemic as it has not been recorded elsewhere in Papua New Guinea, neither from herbarium specimens nor during the recent extensive fieldworks. Much of Milne Bay Province’s lowland rainforest has been, or is being, logged ( Shearman et al. 2009) and the type locality is not inside a protected area, and surrounded by human settlements and by Alotau town, so may be lost in the near future.

Specimens examined ( paratypes). Cultivated plant grown on from Papua New Guinea, Milne Bay Province, Alotau town, on tree along the beach, living accession NS08­077, vouchered at the Singapore Botanical Garden , Singapore, on 25 Sept. 2013 as Rodda , M. MR426 ( SING) .

Notes — Hoya liddlean a is most similar to the widespread (yet endemic to New Guinea) H. onychoides because both species have inflexed ‘claw-like’ corolla lobes and oblong corona lobes. They can be easily separated because the inner surface of the corolla of H. onychoides is glabrous (except a few scattered hairs inside at the base of the staminal corona and along margins) while in H. liddleana it is pubescent throughout inside. In H. onychoides the corona is distinctly conical and about as tall as wide, dark wine-red, while the corona of H. liddleana has a conical centre with prominent spreading outer processes and it is about half as tall as wide, cream, with pink or maroon centre.

Hoya liddleana is also similar to the recently discovered H. stenaokei Simonsson & Rodda (name improved, originally H. stenakei ; IPNI 2021), once again endemic to New Guinea. Both species have the inner surface of the corolla pubescent. The two species can be separated based on the shape of the corolla (inflexed in H. liddleana and rotate in H. stenaokei ) and the shape of the corona (star-shaped with lobes oblong and only basally bilobed at the outer tip in H. liddleana ; almost pentagonal with lobes rhomboid and distinctly bilobed at the outer tip in H. stenaokei ).