Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang, 2022

Zhang, Cai-Fei, Wang, Yan, Chen, Feng, Zhou, Hou-Lin, Liao, Miao, Odago, Wyclif Ochieng, Hu, Guang-Wan & Wang, Qing-Feng, 2022, Vincetoxicum pingtaoanum (Apocynaceae: Asclepiadeae), a new species from the Three Gorges District in Central China, Phytotaxa 564 (1), pp. 59-70 : 61-65

Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang , sp. nov. ( Figures. 2–4 and 5 : A).

Vincetoxicum pingtaoanum is similar to V. henryi , but it can be easily distinguished by the longer petioles (5–16 mm vs. 2–3 mm), long inflorescences (2.5–6 cm vs. 1–2 cm) with a rachis (vs. without a rachis and umbel-like) that are mostly longer (vs. shorter) than leaves, greenish-yellow (vs. purplish red) corollas with linear-lanceolate lobes ca. 5 mm (vs. triangular-ovate less than 2 mm) long ( Figure 5 ). Additionally, it is similar to V. emeiense based on the corolla shapes, but differs in the yellowish green (vs. yellowish brown) corollas, shorter inflorescences (2.5–6 cm vs. 7–11 cm), coronas attached above the upper half gynostegia (vs. inserted near base of gynostegia) with obtuse (vs. truncate) lobes ( Figure 5 ), and horizontal (vs. ascending) caudicles.

Type:— CHINA. Chongqing City, Wuxi County, Lanying , Lanying Grand Canyon , 109.835471°E, 31.437667°N, 758 m a.s.l., path side and on rocks in the valley, 13 April 2021, Feng Chen, Hou-Lin Zhou, Xue-Bing Shi et al. YTL20-409 (Holotype: HIB! [ HIB0208169 ]; isotypes: CQNM!, PE!) .

Evergreen woody lianas. Stems green, 1–1.5 mm in diameter, striated, glabrous except for a ring of trichomes around the nodes. Petioles 5–16 mm long, purplish, adaxially densely puberulent along the two sides of the grove, glabrescent when old, uppermost with 4–6 glands; leaf blades thinly coriaceous, lanceolate, lanceolate-ovate, sometimes ovate or elliptic especially when young, green, reddish when young, lower older ones 6–8 × 2.2–3 cm, upper ones 2.2–6.5 × 0.8–1.6 cm; base obtuse, cuneate or rounded, apex attenuate to acuminate, sometimes acute; midrib raised on both surfaces, lateral veins 4 –5 pairs, obscure in younger ones, glabrous except for a few trichomes on main vein, veins of older leaves prominently pale and reticulate. Inflorescences slender, with (2–) 9–14 flowers, 2.5–6.5 cm long, mostly with two cymules (each with 4–6 flowers) separated by a rachis, rarely 2- or 3-branched and zigzagging, usually longer than the adjacent leaves; peduncles 17–34 mm, longer than pedicles, glabrous; bracteoles ciliate. Pedicels slender 13–23 mm, purplish, glabrous. Calyx lobes purplish, triangle-ovate, ca. 1.5 × 0.7 mm, abaxially sparsely puberulent, each with a dark brown gland between adjacent lobes. Corolla yellowish green, purplish at the throat, deeply lobed, starfish-like, ca. 1 cm in diameter, slightly convex, exterior glabrous, interior minutely hairy; lobes spreading, twisted clockwise, ca. 5 × 1 mm, linear-lanceolate, margins revolute, apex rounded. Gynostegium green ca. 2 mm tall. Staminal corona 2–2.3 mm in diameter; lobes fleshy, ovoid, dorsally rounded, ca. 0.5 mm long, radiating from the stamina column and adnate to the upper half of the anthers.Anthers oblong-rhomboid, apex broadly triangular, subacute, inflexed; anther wings 0.5 mm long; apical appendages with conspicuous membranous margin. Pollinarium with two pollinia connected via caudicles to corpusculum; corpuscular narrowly ellipsoid, brownish, ca. 0.12 × 0.04 mm; caudicles horizontal, fusiform, 0.1 mm long; pollinia oblong-reniform, ca. 0.2 × 0.14 mm, apically attached to caudicles. Style-head flat. Follicles single or paired, narrowly fusiform, brownish, 52–55 × 5–6 mm, glabrous. Seeds brownish-black, ca. 7 × 2–2.5 mm, bottle-shaped, much compressed with one side nearly flat and slightly convex & papillose on the other, margins thinner; coma 15–21 mm long.

Etymology:—The specific epithet ‘ pingtaoanum ’ is in honor of Prof. Ping-Tao Li (Ṫfflṧ, P.T. Li; 1936–) from South China Agriculture University, for his contributions to the taxonomy of Chinese Apocynaceae .

Vernacular name:—Following a tradition of using geographic names as part of the plant vernacular names, we suggest ‘Three Gorges swallow-wort’ as the English common name and ‘Sanxia Baiqian (三ΚƦÑ)’ as the common Chinese name for the new species.

Habitat:— 300–1200 m a.s.l, growing on rocks in open or semi-open areas.

Phenology:—Flowering from April to August; exact fruiting period unknown, but the last growing season’s fruits with mature seeds can be found in April.

Distribution and conservation status:— V. pingtaoanum is currently known only from five localities in the Three Gorges District in Central China ( Fig. 1 ). Three localities are in the north of Yangtze River in Wushan and Wuxi Counties, while the other two are in the south of Yangtze River in Fengjie County. The direct distance among the five localities ranges from about 7.5 km to 75 km. Additionally, this species is expected to be found in the Hubei section of the Three Gorges District, especially in the nearby Badong, Zhushan, and Zhuxi counties ( Fig. 1 ). However, the total occupancy area of V.pingtaoanum is estimated to be no more than 100 km 2 and is projected to decline because of continuous human activities and global climate changes. Thus, it is assessed as vulnerable (VU: B2 ab (ii, iii)) according to the IUCN criteria.

Additional specimens examined (Paratypes):— CHINA. Chongqing. Fengjie County, [Xinglong Town], Xinhe, Guohekou , 700 m, in the humid forest along the roadside, 28 April 1964, Hong-Fu Zhou & He-Yi Su 107855 ( IBSC! [0521747, 0521748]); Wushan County , Guanyang Town , Xinmin Village , 1200 m, on rocks near the bamboo woodland, 20 September 2021, Hou-Lin Zhou in Cai-Fei Zhang 6512 ( HIB!) .

Observations:— CHINA. Wushan County, Guanyang Town , Xinmin Village , 1200 m, on rocks near the bamboo woodland photographed by Hou-Lin Zhou in May and August 2020 ( Fig. 3 : B); Wushan County, Pinghe , 31.275212°N, 110.007323°E, 300 m, in valley, photographed by Hou-Lin Zhou on 11 May 2022; Fengjie County, Xiaozhai , Tiankeng , 600 m, on rocks along the path side, photographed by Hou-Lin Zhou on 16 May 2019 ( Fig. 3 : C, D; Fig. 4 : A, B).

Figures

FIGURE 1. Distribution of Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang in the Three Gorges in Central China.

FIGURE 2. Holotype of Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang (HIB [HIB0208169]). Photographed by Cai-Fei Zhang.

FIGURE 3. Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang. A–B, habit; C–D, flowering branch; E–F, inflorescence. A, E, F photographed by Feng Chen from the type locality; B photographed by Hou-Lin Zhou from Fengjie County; C, D photographed by Hou-Lin Zhou from Wushan County.

FIGURE 4. Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang. A, leaf on lower stem, adaxial (leaf) and abaxial (right) surfaces; B, leaf on upper stem, adaxial (leaf) and abaxial (right) surfaces; C, flower in back view; D, flower in front view; E, flower in top view; F, gynostegium in top view; G, gynostegium and corona in side view; H, dissected gynostegium; I, pollinarium; J, compressed seeds with one surface slightly convex and papillose (left) and the other surface nearly flat (right); K, infructescence. C, D photographed by Hou-Lin Zhou from Wushan County; A, B photographed by Yan Wang from Hou-Lin Zhou in Cai-Fei Zhang 6512; E–K photographed by Yan Wang and Cai-Fei Zhang from the type collection.

FIGURE 5. Similar species Vincetoxicum henryi (A–C), V. insigne (D–F), and V. microcentrum (G–I). A, D, G, flowering plant; B, E, H, inflorescence; C, F, I, flower in top view; A, B photographed by Hou-Lin Zhou from Wushan County; C photographed by Cai-Fei Zhang from Hou-Lin Zhou in Cai-Fei Zhang 6531 (HIB); D–F photographed by Rui Tang from Daocheng County, Sichuan Province, China; G–I photographed by Cai-Fei Zhang and based on Miao Liao ZJLM02 (HIB).