Vincetoxicum xinpingense H. Peng & Y.H. Wang, 2018

Jiang, Li-Qiong, Li, Yuan-Yuan, Zhu, Xin-Xin, Wang, Yue-Hua & Peng, Hua, 2018, Vincetoxicum xinpingense (Asclepiadeae, Asclepiadoideae, Apocynaceae), a new species from Yunnan Province, China, Phytotaxa 361 (1), pp. 56-64 : 57

Vincetoxicum xinpingense H. Peng & Y.H. Wang , spec. nov. ( Figs. 1–3 )

Vincetoxicum xinpingense is distinguished from V. sublanceolatum ( Miquel 1866: 128) Maximowicz (1876: 796) mainly by its horizontal (vs. pendulous in V. sublanceolatum ) pollinia, corolla with a diameter of 2.1–3 cm (vs. 0.7–1.5 cm in V. sublanceolatum ), corona 2/3 of the length of anthers (vs. far shorter than anthers in V. sublanceolatum ). Vincetoxicum xinpingense can also be distinguished from Tylophora forrestii M.G. Gilbert & P.T. Li (1995: 13) by its dark purple (vs. yellowish green in T. forrestii ) corolla with a diameter of 2.1–3 cm (vs. c. 1.2 cm in T. forrestii ), corona ovoid (vs. narrowly ovoid in T. forrestii ), and apex of corona lobes obtuse (vs. acute in T. forrestii ).

Type: — CHINA. Yunnan: Xinping County, Ailao Mountains , 23°58 ′ 24 ″ N, 101°31 ′ 30 ″ E, 2030 m, 23 May 2017, H. Peng, Z.H. Wang & L. Chen XP314 (holotype: KUN! [KUN1344773]; isotypes: K!, KUN! [KUN1344774], PE!, TI!) .

Perennial twining herbs, with colourless latex. Stem slender, terete, branched, sparsely pubescent with short curved trichomes in one or two lines. Leaves opposite; lamina chartaceous, ovate-oblong or elliptic, 7.4–12.5 × 3.5–6.5 cm, margin and nerves on both surfaces pubescent, elsewhere glabrous, apex acute to acuminate, base truncate or retuse, margin entire; petiole 1.3–4.9 cm long, usually with two glands, upper surface grooved, both surfaces densely covered with curved trichomes. Inflorescence dichasial, axillary, 1–2 per axil, flowers (1–) 4–10 (–12); peduncle 2.2–6.6 cm long, puberulent, pedicel slender, 0.5–3.0 cm long, puberulent. Calyx rotate, lobes 5, lanceolate, apex acute, glabrous, with five basal glands. Corolla rotate, dark purple, 2.1–3 cm in diameter; deeply 5-lobed, lobes narrowly lanceolate, 0.8–1.4 × 0.1–0.4 cm, apex truncate, glabrous on both surfaces, margin recurved; corona 3/5 as long as gynostegium, dark purple, deeply 5-lobed, lobes adnate to surface of gynostegium, c. 0.8 × 0.6 mm, ovoid, fleshy; connective appendage membranaceous, ovate, c. 0.59 × 0.72 mm, pollinia 2 per pollinarium, horizontal; corpusculum oblong, c. 0.1 × 0.03 mm; pollinia ellipsoid, c. 0.23 × 0.16 mm; caudicle c. 0.08 mm long. Follicles fusiform, c. 8 × 2.3 cm, glabrous, solitary. Seeds flat, ovate, c. 7 × 5 mm, blackish brown, coma c. 4.3 cm long, white.

Phenology: —Flowering from May to July and fruiting from June to September.

Conservation Status: —Currently, V. xinpingense is only known from three adjacent locations in Ailao Mountains. However, these locations have all been developed into scenic area. In the present survey, very few mature plants (less than 100) were found. The extent of occurrence for V. xinpingense is less than 500 km 2. The plants are directly threatened by disruptive human activities like tourism. Following the IUCN (2017), V. xinpingense could be considered Endangered [EN B2ab(i, ii, v) + D] in a preliminary conservation statement.

Distribution & Habitat:— Vincetoxicum xinpingense is known from the Ailao Mountains in Xinping County, Yunnan Province, China. It is a perennial twining herb growing in the mid-montane humid evergreen broad-leaved forest at an elevation of about 2030 m. The dominant species of the community include Schima wallichii ( Candolle 1824: 528) Korthals (1842: 143) ( Theaceae ), Camellia cuspidata ( Kochs 1900: 586) H.J. Veitch (1912: 228) ( Theaceae ), Rhododendron leptothrium I. B. Balfour & Forrest (1919: 84) ( Ericaceae ), Styrax grandiflorus J.F. Gmelin (1792: 659) ( Styracaceae ), and Symplocos groffii Merrill (1917: 107) ( Symplocaceae ). The dominant shrubs of the region contain Ternstroemia gymnanthera ( Wight & Arnott 1834: 87) Beddome (1871: 91) ( Theaceae ), Osmanthus matsumuranus Hayata (1911: 192) ( Oleaceae ), Illicium verum J.D. Hooker (1888 : pl. 7005) ( Illiciaceae ), and Decaisnea insignis ( Griffith 1855: 187) J.D. Hooker & Thomson (1855: 350) ( Lardizabalaceae ). The main herbs consist of Elatostema tenuicaudatum W.T. Wang (1980: 31) ( Urticaceae ), Ophiorrhiza hispida J.D. Hooker (1880: 83) ( Rubiaceae ), Asplenium unilaterale var. udum Atkinson & C.B. Clarke (1880: 481) ( Aspleniaceae ), and Polystichum nudisorum Ching (1941: 71) ( Dryopteridaceae ).

Etymology: —The specific epithet ‘ xinpingense ’ refers to ‘Xinping County’, from where the species is found.

Figures

FIGURE 1. Vincetoxicum xinpingense.A. plant; B. close up of pubescent stem; C. glands at the base of lamina; D. corolla; E. gynostegium; F. abaxial view of stamen; G. adaxial view of stamen; H. pollinarium; I. ovary, cross section; J. follicle; K. seed. Drawn by L. Wang from H. Peng, Z.H. Wang & L. Chen XP314 (KUN).

FIGURE 2. Vincetoxicum xinpingense (at the type locality). A. habitat; B. root; C. twining stem; D. follicle; E. flowers; F. leaves. Photographed by L.Q. Jiang (A–C) and Y.Y. Li (D–F).

FIGURE 3. Morphology of corona and gynostegium of Vincetoxicum xinpingense. A. abaxial view of corona and gynostegium; B. top view of corona and gynostegium; C. style-head; D. abaxial view of corona; E. connective appendage; F. pollinia, showing its position; G. calyx and ovary; H. pollinarium. Photographed by L.Q. Jiang from H. Peng, Z.H. Wang & L. Chen XP314 (KUN).