Hoya lucida Simonsson & Rodda, 2022

Rodda, M. & Simonsson, N., 2022, Contribution to a revision of Hoya (Apocynaceae: Asclepiadoideae) of Papuasia. Part II: eight new species, one new subspecies, Blumea 67 (2), pp. 139-155 : 146-149

Hoya lucida Simonsson & Rodda , sp. nov. — Fig. 9 , 10

Similar to Hoya magnifica P.I.Forst. & Liddle in having large narrowly elliptic to broadly ovate leaves, 6–25 cm long, and white campanulate flowers,> 3.5 cm diam,but distinguished by the stem and leaf pubescence (glabrous or sparsely pubescent in H. lucida vs densely pubescent in H. magnifica ), and by the size and shape of the calyx lobes (narrowly lanceolate, 4–6 mm long in H. lucida vs lanceolate to ovate, 1.3–1.6 cm long in H. magnifica ). — Type: M. Rodda & E. H. Yap MR 2143 (holo SING; iso K, L, LAE), cultivated plant grown on from Papua New Guinea, Morobe Province, Garaina valley, along trail to Mt.Bishrop, NS 12­072, vouchered at the Singapore Botanic Gardens on 25 May 2021 .

Etymology. The specific epithet ‘ lucida ’ (Latin lucidus: light or bright), refers to the bright white showy flowers of the species.

Climber, epiphytic, latex white. Stems cylindrical, 3–15 mm diam, glabrous (sometimes sparsely pubescent when young), internodes 5–30 cm long. Roots adventitious. Leaves: petiole terete, channelled above, 1.5–2.5 by c. 0.3 cm, glabrous (pubescent when young); lamina variable in shape from narrowly elliptic to broadly ovate, succulent, (6–)10–25 by 3–15 cm, apex rounded to acuminate, base rounded or attenuate; glabrous (sparsely pubescent above when young); venation pinnate, midrib depressed on adaxial surface, secondary veins 5–10 each side. Basal colleters in groups of 5–7, oblong, 0.5–0.7 mm long. Inflorescence one per node, positively geotropic, pseudo-umbelliform, consisting of 5–15 flowers; peduncle extra-axillary, terete, 1–3 cm by 3–8 mm, older peduncles forming a rachis from previous flowerings, glabrous to pubescent; pedicels filiform, 30–40 by c. 1.5 mm, glabrous to sparsely pubescent. Calyx 12–15 mm diam; lobes narrowly lanceolate, 4–6 by 2–3 mm, apex acute, outside glabrous (sparsely pubescent), inside glabrous, ciliate. Basal colleters 2–4 in each sinus, narrowly acute, c. 0.5 mm long. Corolla rotate to broadly campanulate, 3.5–6 cm diam when flattened, snow-white, sometimes with red marking beneath corona; tube 10–12 mm long, outside glabrous, inside pubescent only beneath corona and near margins with short hairs; lobes deltate, 12–15 by 10–14 mm, apex acuminate, outside glabrous, inside pubescent along margins with short hairs. Corona staminal, 5–6 mm high, 8–12 mm diam, cream-white; lobes ovate or round to rhomboid, c. 3 by 5 mm, with inner process pointing diagonally and not covering the style head, c. 2.5 by 0.5 mm, apex acuminate, and a spreading or diagonally held outer process, c. 3.5 by 3 mm, apex rounded, with basal revolute margins. Pollinia oblong, 1000–1100 by 400–500 µm, with pellucid margin; corpusculum ovoid, 500–600 by 300–400 µm; caudicles attached towards the base of the corpusculum, 200–300 µm long. Ovary c. 3 mm long, conical, glabrous at base, pubescent near tip. Fruit and seed not observed.

Distribution — Widely distributed in New Guinea, with most records in the more explored provinces of Madang and Morobe. However, several collections in herbaria are difficult to assign to either H. lucida or to H. calycina Schltr. subsp. glabrifolia P.I.Forst. & Liddle , especially when the characteristic buds are not present.

Habitat & Ecology — It inhabits montane forests between 800 and 1800 m altitude, where it grows as an epiphyte in both primary and mature secondary forests, on exposed trees along forest edges, paths or rivers, rarely inside the forest in full shade. Occasionally seen recolonising mature trees in subsistence gardens, if there are extant populations in primary forests nearby, showing an ability to recolonize disturbed areas.

Conservation status — Least Concern (LC; IUCN 2012). A species occurring over a large area in Morobe and Madang provinces but under-represented in herbarium collections.

Specimens examined ( paratypes). Cultivated plant grown on from Papua New Guinea, NS12­106, vouchered at the Singapore Botanic Gardens on 1 Apr.2021 as M . Rodda & E. H . Yap MR 2133 ( SING);cultivated plant grown on from Papua New Guinea, NS12­087, vouchered at the Singapore Botanic Gardens on 29 July 2021 as M . Rodda & E. H . Yap MR 2159 ( SING); cultivated plant grown on from Papua New Guinea, Morobe Province, Garaina valley,along trail to Mt.Bishrop NS12­078, vouchered in Papua New Guinea, Eastern Highlands Province, Ukarumpa, on 2 Dec. 2013 as N . Simonsson & F . Juhonewe NS 0083 L ( SING, LAE); cultivated plant grown on from Papua New Guinea, Morobe Province, Garaina valley, Saureli , camp 1, newly cre- ated garden in primary forest area. 1612 m, NS12­082, vouchered in Papua New Guinea, Eastern Highlands Province, Ukarumpa, on 2 Dec. 2013 as N . Simonsson & F . Juhonewe NS0082 L ( LAE, SING) .

Notes — As mentioned in the diagnosis,the flowers of H. lucida are similar in size, corolla and corona morphology to these of H. magnifica , but the two species can be separated on size and shape of the calyx lobes (narrowly lanceolate, 4–6 mm long in H. lucida , lanceolate to ovate, 1.3–1.6 cm long in H. magnifica ) and stem and leaf pubescence (glabrous or sparsely pubescent in H. lucida , densely pubescent in H. magnifica ).

Based on herbarium records, specimens of H. lucida are often misidentified as H. calycina subsp. glabrifolia because of the large glabrous or glabrescent leaves and large flowers. Both taxa are widespread in the mountains of New Guinea and cannot be distinguished when not in flower, but upon seeing living materials we noticed that H. lucida has flattened buds and more broadly campanulate corollas that are thinner and flexible upon touch, while the buds are rounded and the corolla is stiffer and succulent in H. calycina subsp. glabrifolia . The scent from cultivated specimens from Morobe and Madang is similar to that of Lily of the Valley ( Convallaria majalis L., Asparagaceae ).

Figures

Fig. 9 Hoya lucida Simonsson & Rodda. a. Flower (from underneath), b. flower (from above); c. bud; d. corona (side view); e. corona (from above); f. calyx and ovary; g. pollinarium (a–c: M. Rodda & E.H. Yap MR2133, SING; d–g: M. Rodda & E.H. Yap MR2143, SING). — Photos: M. Rodda.

Fig. 10 Hoya lucida Simonsson & Rodda. Habit with inflorescence (from M. Rodda & E.H. Yap MR2143, SING). — Photo: M. Rodda.