Cynanchum pingtaoi S.Jin Zeng, G.D.Tang & Miao Liao, 2024

Liao, Miao, Zeng, Si-Jin, Zeng, Lin-Ya, Yin, Hai-Jun, Yan, Mao-Lin, Zhang, Cai-Fei & Tang, Guang-Da, 2024, A new species and a replacement name in Cynanchum (Apocynaceae, Asclepiadeae) from China, PhytoKeys 241, pp. 49-63 : 49

Cynanchum pingtaoi S.Jin Zeng, G.D.Tang & Miao Liao sp. nov.

Figs 3 , 4

Type.

China. Yunnan: Dehong Dai and Jingpo Autonomous Prefecture, Ruili City , Nongdao Town , Tongbiguan Provincial Nature Reserve , 23°57'N, 97°32'E, elev. 839 m, 24 Aug. 2020, Si-Jin Zeng & Lin-Ya Zeng SJ 4825 (holotype, IBSC[IBSC1009908!]; isotypes, IBSC [IBSC1009907!], [IBSC1009909!], [IBSC1009910!]) .

Diagnosis.

Cynanchum pingtaoi resembles C. longhushanense , differing by its broadly ovate corolla lobes (vs. oblong), the purple-red inner surface of the corolla (vs. white), and the corona-scales apex connivent, slightly exceeding the corolla throat (vs. corona-scales apex connivent, not exceeding the throat of the corolla).

Description.

Twining liana. White latex in stems and leaves. Branchlets fistulous, smooth, glabrous, slightly woody. Leaves opposite; petiole 6-14 cm long, smooth, sparsely white puberulent, later glabrescent, with small yellowish-brown glands at the apex, nodes with small glands; leaf blade deeply cordate to reniform, 7-15 × 4-13 cm, membranous, base cordate, apex acuminate, margin entire, adaxial surface dark green, glabrous, abaxial surface light green, sparsely white puberulent on veins, gradually glabrescent later; basal veins five or seven, palmate, secondary veins three to five pairs, pinnate, tertiary veins reticulate, smooth adaxially, raised abaxially. Inflorescences extra-axillary, subumbellate to subracemic, 5-11 flowers; peduncle 10-12 cm long, smooth; pedicel 3.0-5.5 cm long, smooth, sparsely white puberulent near the base, base with bracteoles triangular, ca. 0.1 × 0.1 cm. Calyx yellowish green, basally fused, lobes elliptic, ca. 0.6 × 0.5 cm, inside the base with small glands, apices obtuse, margins ciliate. Corolla campanulate, glabrous, external surface greenish white, inner surface purple-red, 3.3-3.5 cm in diam; lobes slightly longer than tube, tube 1.2-1.4 cm, lobes broadly ovate, 1.3-1.8 × 1-1.2 cm, apices reflexed, overlapping to the right. Corona lobes linear-subulate, white, separate, ca. 1.1 cm long, inserted at base of gynostegium, longer than gynostegium, corona-scales apex connivent, slightly exceeding corolla throat. Anthers ca. 0.7 × 0.4 cm, apices with inwardly incurved wings. Stigma broadly rounded, slightly depressed, white. Pollinia 2 per pollinarium, ellipsoid, yellow, pendulous, ca. 0.13 × 0.08 cm, caudicle ca. 0.05 cm long, retinaculum ca. 0.1 cm long. Follicles solitary, fusiform, ca. 14.5 cm long, ca. 5 cm diam., glabrous, with a thick fibrous pericarp, triangulate, apex curved outwards; seeds ovoid, 0.8 cm × 0.6 cm, tipped with a white silky coma; coma 3.8-4.2 cm long.

Etymology.

The specific epithet Cynanchum pingtaoi honors the eminent botanist Ping-Tao Li (李秉滔), who is an expert in the Apocynaceae .

Chinese name.

Bingtao Dahuateng (秉滔大花藤).

Distribution.

Endemic to China. Only one population was found at the border of China-Myanmar in Ruili, Yunnan Province, China. Fig. 5 .

Habitat and phenology.

This species occurs near open woods at an elevation of about 850 m. Flowering was observed from September to October, fruiting from November to December.

Provisional IUCN assessment.

The species is currently known only from the type locality, where only a few individuals were seen. Suitable habitat exists in the proximity of the type locality. Nevertheless, as there is no reliable information on the population size or distribution of this species, we propose to treat it as Data Deficient (IUCN 2019).

Notes.

The large and reniform leaves, campanulate corolla, and lanceolate corona indicate that this species is morphologically close to the former Raphistemma species, which have been included in Cynanchum ( Khanum et al. 2016). The molecular phylogenetic analyses also showed that Cynanchum pingtaoi is sister to C. pulchellum + C. longhushanense (Fig. 1 ; Suppl. material 3). We do not currently possess molecular data of C. hooperianum , but the new species can be distinguished from this species by the purple-red inner surface of the corolla (vs. white inner surface of the corolla with purple spots near the top of the corolla lobes), the connivent corona-scales apex, slightly exceeding the corolla throat (vs. corona-scales apex separate, and reaching the middle of the corolla-segments or somewhat further), the longer calyx-segments (6 mm vs. 3-4 mm), and the longer corolla-tubes (12-14 mm vs. 8-9 mm).

Figures

Figure 1. Simplified maximum likelihood tree of Cynanchum based on two nuclear regions (nrETS and nrITS) and three plastid markers (rps 16 and trnL introns, and trnL-F spacer). Bootstrap support values are given for each node. See Suppl. material 3 for maximum likelihood tree. Clade designations follow those of Khanum et al. (2016) and names in parentheses are the corresponding names that were used in Khanum et al. (2016).

Figure 3. Cynanchum pingtaoi S. Jin Zeng, G. D. Tang & Miao Liao a follicle and leaves b inflorescence c glands at the base of leaf d top view of flower e side view of flower with two corolla lobes removed f calyx g corolla lobes (each lobe attached to part of the corolla tube), outer surface on the right, inner surface on the left (four drawn) h corolla separation, showing gynostegium with corona lobes i pollinarium j seed. Illustration based on Si-Jin Zeng & Lin-Ya Zeng SJ 4825 (IBSC), and drawn by Ding-Han Cui.

Figure 4. Cynanchum pingtaoi S. Jin Zeng, G. D. Tang & Miao Liao a habitat b inflorescence and leaf c inflorescence d flower buds e top view of flower f bracteoles at base of pedicel g side view of flower h corolla and corona separation, showing gynostegium, corona and corolla lobes (outer surface: upper right hand corner; inner surface: to the left of the outer surface) i pollinarium from dry specimen j young seeds k longitudinally opened half follicle showing seed arrangement l follicle, different views to show the three ribs m transverse section through follicle n follicle and leaves. All photos based on Si-Jin Zeng & Lin-Ya Zeng SJ 4825 (IBSC).

Figure 5. Distribution map of Cynanchum pingtaoi and the three Cynanchum species formerly were considered to belong to Raphistemma based on specimens cited in Suppl. material 4. The base map [No. GS (2016) 1666] was downloaded from http: // bzdt. ch. mnr. gov. cn /.