Hoya tarikuensis Rodda & Simonsson, 2022

Hoya tarikuensis Rodda & Simonsson View in CoL , sp. nov. — Fig. 14 View Fig

Similar to Hoya uncinata Teijsm. & Binn. from Java and Sumatra in the deeply lobed rotate corolla with inflexed lobes but distinct in the shape of the corona (stipitate, with corona lobes laterally compressed in H. uncinata vs sessile with spreading lobes in H. tarikuensis ). — Type: W. M. Docters van Leeuwen 9869 (holo L [ L.2720319]; iso K), Indonesia, Papua Province, Rouffaer River , 175 m, Aug. 1926 .

Etymology. Named after the type locality by Tariku river (Sungai Tariku), formerly known as Rouffaer river.

Climber, latex colour unknown. Stems cylindrical, slender, 2–3 mm diam, glabrous, internodes 4–15 cm long. Roots not observed. Leaves: petiole terete, channelled above, 5 –10 by 1.5–2 mm, pubescent to glabrescent; lamina elliptic-lanceolate, very coriaceous when dry, 4–15 by 1.5–7 cm, glabrous, apex acuminate to acute, base rounded to acute; venation pinnate, midrib depressed on adaxial surface, secondary veins 3 – 6 each side, barely visible. Colleter 1, along midrib and slightly sunken in, 2–3 mm from lamina base, broadly conical, c. 0.5 by 0.5 mm. Inflorescence one per node, tropism unknown, pseudo-umbelliform, consisting of 3–6 flowers; peduncle extra-axillary, terete, 4–10 cm by 1–2 mm, glabrous, older peduncles forming a rachis from previous flowerings; pedicels filiform, 11–14 cm by c. 0.3 mm, glabrous. Calyx 1.5–2 mm diam; lobes deltate, 0.5–0.7 by 0.2–0.3 mm, apex acute, glabrous. Basal colleters one at each calyx lobe sinus, conical, c. 0.1 mm long. Flowers white. Corolla rotate with inflexed lobes, 8–10 mm diam when flattened; tube c. 1 mm long, outside glabrous, inside pubescent, glabrescent towards the centre; lobes ovate, 3–4 by 2.5–3 mm, margins reflexed apex acute, outside glabrous, inside pubescent. Corona staminal, sessile, c. 1 mm high, 3.5– 4.5 mm diam; lobes spreading, ellipsoid, 1.4–2.2 by 0.7–1 mm, inner process acuminate, outer processes raised, rounded, with basal revolute margins. Pollinia oblong, c. 380 by 120 µm, with pellucid margin; corpusculum oblong, with slight constriction in the middle, c. 120 by 80 µm; caudicles attached in the middle of the corpusculum, c. 80 µm long. Ovary conical, 0.7–1 mm long, glabrous. Fruit and seed not observed.

Distribution — The species is only known from the type locality in Indonesia, Papua Province, by the Tariku River.

Habitat & Ecology — The only data provided on the type specimen indicate that this species was found in hills, in the forest.

Conservation status — Data Deficient ( DD; IUCN 2012 ). Hoya tarikuensis is known only from the type specimen collected 96 years ago .

Notes — Hoya tarikuensis is most similar to H. uncinata , which is not native to New Guinea but found in Java and Sumatra. Hoya uncinata is peculiar in having clear latex. We do not know the latex colour of H. tarikuensis . We suspect that the similarities in corolla shape between the two species do not reflect a close relationship between the species as other features such as the corona and the pollinarium are clearly different: corona stipitate, with corolla lobes laterally compressed in H. uncinata vs sessile with spreading lobes in H. tarikuensis ; corpusculum of the pollinarium almost as large as the pollinium in H. uncinata vs corpusculum less than half as long as pollinium in H. tarikuensis .

In New Guinea the most similar species to H. tarikuensis in habit is H. chloroleuca Schltr. as both species have large thin leaves with acute base in combination with small flowers (c. 1 cm when dry), but H. chloroleuca has rotate corollas, while H. tarikuensis has deeply lobed inflexed corollas. Other species with deeply lobed corollas are H. exilis Schltr. and H. oreostemma Schltr. , but their corolla lobes are reflexed (vs inflexed in H. tarikuensis ). Hoya pulleana (published here) has deeply lobed corollas with inflexed corolla lobes just like H. tarikuensis but the leaves of H. pulleana are ovate to round, 8–16 by 5–12 mm (vs elliptic-lanceolate, 4–15 by 1.5–7 cm in H. tarikuensis ).