Vincetoxicum emeiense S.Y.Zeng & Q.Y.Yang, 2021

Zeng, Si-Yuan, Yang, Qi-Yi, Yu, Jie & Shen, Jian-Yong, 2021, Vincetoxicum emeiense (Asclepiadeae, Asclepiadoideae, Apocynaceae), a new species from Sichuan, China, Phytotaxa 505 (1), pp. 56-62 : 59-60

Vincetoxicum emeiense S.Y.Zeng & Q.Y.Yang , sp. nov. ( Figs.1 , 2 )

Type:— CHINA. Sichuan: Emeishan City, Mount Emei , 29.569 N; 103.391 E, 757 m elev., 19 May 2020, Qiyi Yang 0001 (holotype: HITBC!; isotypes: FAFU) .

Diagnosis:— Vincetoxicum emeiense can be distinguished from V. hui ( Tsiang 1936: 236, pl. 30, f. 20) by several morphological features (summarised in Table 1). V. emeiense has glabrous (vs. yellowish pubescent along 1 side in V. hui ) stem and adaxially puberulent (vs. adaxially glabrous in V. hui ) leaf shape, and with adaxially puberulent and orange to purple (compared with green in V. hui ) corolla.

Plants twining, to 3 m high. Latex transparent. Stem glabrous throughout, slender. Leaves discolorous, ovate to ovatelanceolate, 6–10× 2–3.5cm, papery to membranous, margin finely ciliate, base cordate, truncate or cuneate, apex acuminate, basal veins 3, with three–six conical colleters, 0.2–0.5mm in length, lateral veins 4–5 on each side of the midrib; petiole 1–2cm, pubescent along a single line. Inflorescence one per node, dichasial, axillary, 7–11 cm, longer than leaves, peduncle 0.6–3cm. 8–20-flowered; basal bracts triangular, margin ciliolate; pedicel 0.7–1.5 mm long, glabrous; Flowers buds subsphaeroidal, 2–3 mm in diam. Calyx rotate; sepals linear-lanceolate, margin translucent, with two basal glands. Corolla orange yellow and purple at base, rotate, 6–11mm in diam, tube short, lobes ovatelanceolate, apex acuminate, abaxially puberulent, margin revolute. Corona 2/3 as long as gynostegium, dark red, deeply 5-lobed, lobes elliptic-oblong, adnate to surface of gynostegium, turgid, basally spreading, central extending outward horizontally, convex front slightly concave or flat. Gynostegium sessile, ca. 1.5 mm long, ca. 1 mm in diam; anther-appendages triangular to rounded, entire, incurved; style-head raised, 2-lobed, 0.2–0.3 mm high. Pollinarium: corpusculum ca. 0.2 mm long, margins of the corpuscular cleft straight, caudicles basally inserted on the corpusculum, ca. 0.2 mm long, flattened, straight, thickened at the insertion of the pollinium; pollinia laterally attached to the caudicles, 0.3 mm long, ovate to round in cross-section, oblong. Fruits and seeds not seen.

Phenology:— Flowers were observed in May.

Distribution & habitat:— The new species is so far only recorded from the type locality, Mount Emei, Sichuan Province at an elevation of ca. 757 m, where it grows in evergreen broad–leaved forest.

Etymology: —The specific epithet “ emeiense ” refers to Mount Emei, the locality of the type collection. 峨眉白 Ñ(é Méi Bái Qián) is suggested as a suitable Chinese name for it.

Conservation assessment:— We were able to observe only one individual of V. emeiense in Mount Emei, Sichuan. Because of the steep slope and dense plantation at the type locality, we only surveyed along the road, and no additional population were observed. The investigation has not been thorough enough to fully understand the species natural distribution. Hence, this new species is better regarded as Data Deficient (DD) according to the IUCN Red List categories and criteria ( IUCN 2012).

Notes:— Vincetoxicum emeiense is similar to V. hui and V. koi . in twining herbaceous life form, leaf, pleiochasium and corolla shape, but there are numerous features that can be used to distinguish them. The blade of V. emeiense bears 3–4 lateral veins on each side of the midrib and is adaxially puberulent while the blade of V. hui and V. koi bears 4–5 veins on each side of the midrib and are adaxially glabrous; V. emeiense and V. hui bear tufted colleters at the top of petiole while colleters are missing in V. koi (Fig.3 B, E & H); the inflorescence morphology of these species is very different: they are cymose and compact in V. hui , loosely cymose in V. koi and paniculate in V. emeiense respectively (Fig.3 C, F & I). Then fresh material is available the three species can be distinguished easily by their corolla color, which is greenish and greenish orange in V. hui and V. koi , while it is orange-yellow with a purple base in V. emeiense (Fig. 3 A, D & G). Additionally, the corona is ovate, turgid, crippling outward in V. hui and V. koi , while it is elliptic-oblong, turgid, underpart spreading, extend outward with a long centrifugal concave base in V. emeiense . The differences between the new species and the other two similar species of Vincetoxicum are listed in Table 1.

Figures

FIGURE 1. Vincetoxicum emeiense. (A) plant, (B) colleters at the base of lamina, (C) calyx, (D) corolla, (E) gynostegium, (F) pollinarium. Drawn by Si-Yuan Zeng from Qiyi Yang 0001.

FIGURE 2. Vincetoxicum emeiense (at the type locality). (A) habitat, (B) flowering branch, (C) inflorescence, (D–E) adaxial and abaxial leaf surface, (F–G) corolla lobes, (H) corona and gynostegium in side view, (I) gynostegium in top view, (J) pollinarium, showing its position, (K) pollinarium. Photographed by Ming-Han Li (A & C), Qi-Yi Yang (B, D–G) and Jian-Yong Shen (H–K, the photos were taken from flowers preserved in alcohol).