Jasminanthes borneensis Rodda, 2019

Rodda, Michele, 2019, A revision of Jasminanthes (Apocynaceae) with four new species from Borneo, Phytotaxa 405 (3), pp. 127-146 : 130

Jasminanthes borneensis Rodda , spec. nov. ( Figs 1–3 )

Jasminanthes borneensis is most similar to Jasminanthes suaveolens in lamina shape (elliptic or lanceolate) but distinguished on corolla lobe shape and size, lanceolate or elliptic-ovate 10–30 × 5–9 mm in J. borneensis vs. linear in J. suaveolens , 6–9 × 1–1.5 mm.

Type:— Brunei, Temburong, Kuala Belalong , 200 ft., climber, 18 March 1957, Smythies, B.E., Wood, G.H.S., Ashton, P.S. SAN17365 (holotype SING [SING0121956]; isotypes A, BO n.v., BRI n.v., BRUN, K, KEP, L [L.2716805], SAN, SING n.v.) .

Stems up to 4.5 m long, latex transparent. Leafy stems 2–4 mm in diameter, pubescent with retrorse trichomes; internodes (2.5–)6–10(–20) cm long. Leaves petiolate, petiole channelled above, 1–2.5 cm long, 1–1.5 mm in diameter, pubescent with spreading trichomes, lamina variable, elliptic to lanceolate (6–)9–15(–20) × (2–) 3–6 cm; base round to acute; apex acuminate to caudate with a tip 7–10 mm long; sparsely pubescent along main vein above, elsewhere glabrous, sparsely pubescent underneath more so along the main and secondary veins, basal colleters 2–8 at each lamina base, conical or oblong, 0.2–0.5 mm long, 0.1–0.2 mm wide; lateral veins 4–10 each side. Inflorescences extra-axillary, simple, racemiform, up to 10-flowered; peduncle 1–2.5 cm long, 1.5–2.5 mm in diameter, pubescent, trichomes spreading. Pedicel 8–20 mm long, 1–1.5 mm in diameter, pubescent with spreading trichomes. Flower bud just before anthesis fusiform, 19–35 mm long, c. 5 mm in diameter. Calyx lobes narrowly ovate, lanceolate or almost linear, apex acuminate, 5–12 × 1.5–4 mm, outside very sparsely pubescent, inside glabrous, sparsely ciliate; colleters 1–3 occurring between the lobes, oblong, 0.1–0.35 × 0.1–0.15 mm. Corolla salverform, white to pale green, tube 9–17 mm long, 2–4 mm wide at throat, adaxially with 5 patches 5–7 mm long of retrorse trichomes in the lowermost third of the tube, throat glabrous or sparsely pubescent, abaxially pubescent, sometimes glabrous at the lowermost third, lobes lanceolate or elliptic-ovate, 10–30 × 5–9 mm, base symmetric, apex acuminate, inside glabrous or papillose, outside pubescent or glabrescent. Corona staminal absent; Gynostegium conical, 3.5–5.5 mm high, 1.5–2 mm wide, glabrous. Guide rails 1.5–2.0 mm long. Pollinia erect, oblong, 600–700 mm × 200–250 μm; caudicle c. 100 μm long; corpusculum oblong 500–700 × 250–300 μm. Anther appendages erect, covering the style head, 2–2.2 × 1–1.2 mm. Style head umbonate, c. 1.1 mm in diameter. Ovary bi-carpellate, carpels ovate, 1.3–2 mm long, 0.7–1 mm wide at the base, apically sparsely pubescent. Fruit a single follicle, 10 × 2.5 cm, glabrous, seed ovate, 23–26 × 4–5 mm, not comose.

Etymology:— Named after the island of Borneo where all the specimens of the taxon have been collected.

Distribution and ecology:— Borneo: Malaysia (Sabah and Sarawak), Brunei and Indonesia, West Kalimantan. From the scarce collection information on specimen labels, J. borneensis appears to be restricted to lowland forests from sea level to 500 m a.s.l. and it is often found along rivers.

Conservation status:— Using GeoCAT ( Bachman et al. 2011) the estimated Extent of Occurrence (EOO) is> 50000 km 2 and the Area of Occurrence (AOO) is 28 km 2. Jasminanthes borneensis is likely to occur in many more localities in lowland forests of Borneo and it is therefore assessed as Least Concern (LC, IUCN 2012).

Notes:— Despite being known from only five localities, Jasminanthes borneensis is the most common and variable species in Borneo. The lamina can be elliptic or lanceolate, with specimens with very long and narrow leaves representing the extreme (Rantai Jawa et al. S.8282). The size of the calyx, corolla tube and lobe is also very variable, with specimens with lanceolate leaves having some of the largest flowers. Its seeds are unique among Jasminanthes because they lack the coma of hairs at the germinating end. Despite its morphological variability it is readily distinguished from the other Bornean species. Jasminanthes kinabaluensis , J. maingayi and J. hosei have cordate lamina base vs. J. borneensis has round to acute lamina base. Jasminanthes sarawakensis is smaller in calyx, tube and corolla lobe size, J. suaveolens has shorter and narrower corolla lobes. These differences are summarised in Tab. 1.

Figures

FIGURE 1. Distribution map of Jasminanthes species in Borneo, based on the examined specimens listed. Generated using SimpleMappr (www.simplemappr.net).

FIGURE 2. Jasminanthes borneensis. Form with acute lamina base and pubescent upper corolla tube. A, Flowering branch; B, Calyx and ovary; C, Bud; D, Open corolla; E, A single corolla lobe and section of corolla tube showing the arrangement of the hairs; F, Gynostegium lobe; G, Pollinarium. Based on Chew 1072, drawn by Loh Xiang Yun.

FIGURE 3. Jasminanthes borneensis. Form with round lamina base and glabrous upper corolla tube. A, Flowering branch; B, Calyx and ovary; C, Bud; D, Open corolla; E, A single corolla lobe and section of corolla tube showing the arrangement of the hairs; F, Gynostegium lobe; G, Pollinarium. Based on Sands et al. 5570, drawn by Loh Xiang Yun.