 |
| Hoya sumatrana S.Rahayu & Rodda
in Rahayu & Rodda, 2019.
DOI: 10.5852/ejt.2019.508
|
Abstract
The list of the species of Hoya R.Br. occurring on the Indonesian island of Sumatra is updated and the type citation is clarified. Sixteen taxa are added to the latest checklist. Hoya danumensis subsp. amarii S.Rahayu & Rodda subsp. nov., H. rigidifolia S.Rahayu & Rodda sp. nov., H. solokensis S.Rahayu & Rodda sp. nov., and H. sumatrana S.Rahayu & Rodda sp. nov. are newly described. Hoya parviflora Wight, H. parvifolia Schltr., and H. purpureofusca Hook. are lectotypified.
Keywords: Apocynaceae; Asclepiadaceae; Asclepiadoideae; Indonesia; Marsdenieae
Checklist of the genus Hoya of Sumatra
Class Magnoliopsida Brongn.
Subclass Asteridae Takht.
Order Gentianales Juss. ex Bercht. & J.Presl
Family Apocynaceae Juss.
Genus Hoya R.Br.
Hoya andalensis Kloppenb.
Hoya beccarii Rodda & Simonsson
Hoya brooksii Ridl.
Hoya campanulata Blume
Hoya caudata Hook.f.
Hoya coriacea Blume
Hoya coronaria Blume
Hoya danumensis subsp. amarii S.Rahayu & Rodda subsp. nov.
Etymology The new species is named after Amar Husein Sitompul, who collected the type specimen.
Notes Hoya danumensis subsp. amarii subsp. nov. can be separated from H. danumensis Rodda & Nyhuus (2009) subsp. danumensis because of the shape and size of the corolla that is shallowly campanulate, 20–23 mm in diameter and deeply campanulate, vs 25–35 mm in the latter; in the shape and size of the corona lobes that are ovate-oblong and 5.5–6 × 2.4–2.6 mm in H. danumensis subsp. danumensis vs ovate and 4.5–5 × 2.3–2.5 mm in the new subspecies.
Hoya deykeae T.Green
Hoya diversifolia Blume
Hoya elliptica Hook.f.
Hoya fauziana subsp. angulata Rodda, A.L.Lamb, Gokusing & S.Rahayu
Blumea 63: 144 (Rodda et al. 2018).
Hoya finlaysonii Wight
Hoya forbesii King & Gamble
Hoya glabra Schltr.
Hoya imperialis Lindl.
Hoya kastbergii Kloppenb.
Hoya lacunosa Blume
Hoya lasiantha (Korth. ex Blume) Miq.
Hoya latifolia G.Don
Hoya mitrata Kerr nom. cons.
Hoya multiflora Blume
Hoya obtusifolia Wight
Hoya omlorii (Livsh. & Meve) L.Wanntorp & Meve
Hoya parviflora Wight
Hoya parvifolia Schltr.
Hoya purpurascens Teijsm. & Binn.
Hoya purpureofusca Hook.
Hoya revoluta Wight ex Hook.f.
Hoya rhodostele Ridl.
 |
| Fig. 2. Inflorescence, pollinarium, and leaf. C, E. Inflorescences. D, G. Pollinaria. F. Leaf. C–D. Hoya solokensis S.Rahayu & Rodda sp. nov. (Fadly s.n. leg., BO). E–G. Hoya rigidifolia S.Rahayu & Rodda sp. nov. (S. Rahayu 865 leg., BO).
Photos: Fadly (C), S. Rahayu (E–F), and M. Rodda (D, G).
|
Hoya rigidifolia S.Rahayu & Rodda sp. nov.
Etymology The new species is named for its rigid and stiff leaves.
Notes Hoya rigidifolia sp. nov. flowers only open for a single day. The flowers of H. finlaysonii are also open for a single day and have a similar flower morphology (rotate corolla, ovoid corona lobes of similar size). Both species are, however, easily separated based on leaf characters. Hoya finlaysonii has lanceolate to oblong leaves with pinnate venation, usually darker than the rest of the lamina; H. rigidifolia sp. nov. also has pinnate venation, but additionally it has two basal secondary veins running along the entire length of the lamina. The leaf venation of H. erythrina Rintz (1978) is similar to that of H. rigidifolia sp. nov.; however, both species can be separated based on flower charaters: H. erythrina has flowers with corolla > 15 mm in diameter when flattened, long-pubescent inside, and lasting > 2 days, while H. rigidifolia sp. nov. has flowers with corolla < 12 mm in diameter when flattened, glabrous inside, and lasting one day.
Hoya rintzii Rodda, Simonsson & S.Rahayu
Hoya rundumensis (T.Green) Rodda & Simonsson
Hoya sarcophylla Ridl.
Hoya scortechinii King & Gamble
Hoya sigillatis T.Green subsp. sigillatis
Hoya solokensis S.Rahayu & Rodda sp. nov.
Etymology The new species is named after the collection locality in Solok, Sumatra.
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.
 |
| Fig. 3. Hoya sumatrana S.Rahayu & Rodda sp. nov. A. Buds. B. Inflorescence, from underneath. C. Flower, from top. D. Corolla, from underneath, calyx and pedicel. E. Flower, side view. F. Corona, from underneath. G. Pedicel, calyx and ovaries. H. Pollinarium. Photos: M. Rodda. |
Hoya sumatrana S.Rahayu & Rodda sp. nov
Etymology The new species is named after the Indonesian island of Sumatra.
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.
Hoya uncinata Teijsm. & Binn.
Hoya vitellinoides Bakh.f.
Hoya vitellina Blume
Hoya wrayi King & Gamble
Discussion:
Since Rahayu & Wanntorp (2012), the Sumatran specimens identified as H. erythrostemma Kerr (1939) have been identified as H. rintzii, H. micrantha Hook.f. (Hooker 1883) has been re-determined as H. rundumensis, and H. verticillata was reported as H. parasitica Wall. ex Wight (1834). Nine species have been added to the inventory of Sumatran Hoya (Rahayu & Wanntorp 2012), all described based on Sumatran collections. These are H. andalensis, H. beccarii, H. brooksii, H. deykeae, H. omlorii, H. parvifolia, H. purpurascens, H. sarcophylla, and H. uncinata.
Hoya variifolia is considered a new synonym of H. parviflora. Two further species, H. glabra Schltr (Schlechter 1908) and H. kastbergii, are newly recorded.
The total count of taxa of Hoya known from Sumatra now stands at 43 and includes 41 species and two subspecies
Sri Rahayu and Michele Rodda. 2019. Hoya of Sumatra, An Updated Checklist, Three New Species, and A New Subspecies. European Journal of Taxonomy. 508; 1–23. DOI: 10.5852/ejt.2019.508
