Research Article |
Corresponding author: Si-Jin Zeng ( kaileqixia@gmail.com ) Academic editor: Petra De Block
© 2024 Miao Liao, Si-Jin Zeng, Lin-Ya Zeng, Hai-Jun Yin, Mao-Lin Yan, Cai-Fei Zhang, Guang-Da Tang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Liao M, Zeng S-J, Zeng L-Y, Yin H-J, Yan M-L, Zhang C-F, Tang G-D (2024) A new species and a replacement name in Cynanchum (Apocynaceae, Asclepiadeae) from China. PhytoKeys 241: 49-63. https://doi.org/10.3897/phytokeys.241.111499
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Cynanchum pingtaoi S.Jin Zeng, G.D.Tang & Miao Liao, sp. nov. (Apocynaceae) from Yunnan Province, China, is described and illustrated based on morphological and molecular evidence. Its deeply cordate to reniform leaves and campanulate, large flowers show that it is a member of former Raphistemma Wall., which has been included in Cynanchum L.. It is different from all former Raphistemma species by the broadly ovate corolla lobes, purple-red corolla and connivent corona tip slightly exceeding the corolla throat. Meanwhile, Cynanchum longhushanense G.D.Tang & Miao Liao, nom. nov. is proposed as replacement name for Raphistemma brevipedunculatum Y.Wan, which was considered a synonym of Cynanchum hooperianum (Blume) Liede & Khanum but is here reinstated as a distinct species because of significant morphological differences.
Cynanchum hooperianum, Cynanchum longhushanense, Cynanchum pingtaoi, morphology, phylogeny, Raphistemma, taxonomy
Cynanchum L. is one of the largest genera of Asclepiadeae (Apocynaceae) and is mainly distributed in Africa and Asia, but it occurs as well in the New World (
Cynanchum is a large and complex genus, and the Chinese representatives of Cynanchum have not been completely revised since the “Flora of China” (
During a field survey in 2020, we collected an unknown species in Ruili, Yunnan. This species has the typical characters of former Raphistemma species with large and reniform leaves, and large and campanulate corollas. Four names were recorded in Raphistemma: R. ciliata Hook.f. was treated as a synonym of Pergularia daemia (Forssk.) Chiov. (
For the new species, field observations were done and a collection made in Ruili City, Yunnan Province (specimen voucher: Si-Jin Zeng & Lin-Ya Zeng SJ4825 (IBSC)). We collected a living sample of R. brevipedunculatum from the type locality (Longhushan Nature Reserve, Longan County, Guangxi Zhuang Autonomous Region (specimen voucher: Miao Liao LM78 (IBSC)). Literature referring to Cynanchum pulchellum, C. hooperianum, and R. brevipedunculatum was consulted, including protologues (
We obtained total genomic DNA of the new species and R. brevipedunculatum from fresh leaf material dried in silica gel with the plant genomic DNA kit (DP305, Tiangen, Beijing, China). The samples were sent to Novogene (Tianjin, China) for library preparation (350 bp) for genome skimming sequencing. We used an Illumina HiSeq 2000 to conduct a paired-end sequencing (150 bp), generating 10 Gb raw data for each sample. After quality control of the raw data using fastp 0.19.7 (
A plastid genome of Apocynum venetum L., a continuous sequence (18S-ITS1-5.8S-ITS2-26S) of the ribosome genome of Asclepias albicans S.Watson, and the nrETS of Calciphila galgalensis (Liede) Liede & Meve and Cynanchum adalinae (K.Schum.) K.Schum. (GenBank accession numbers: MT313688, JN665082, LN896997, and LN897003) were used as respective references. We employed Geneious Prime 2019 (https://www.geneious.com) to annotate and extract three plastid DNA markers (one spacer of trnL-F and two introns of rps16 and trnL) and two nuclear DNA regions (nrITS: internal transcribed spacer; nrETS: external transcribed spacer). New sequences of the five loci were uploaded to GenBank with accession numbers OP810602–OP810613 and OP853101–OP853103 (https://www.ncbi.nlm.nih.gov/).
Sequences of the new species and R. brevipedunculatum were added to a reduced matrix of
We aligned sequences of the three plastid markers and two nuclear regions separately using the MUSCLE optional in the software MEGA v.7.0.26 (
We used RAxML-HPC2 8.2.12 on XSEDE (
The new species resembles Cynanchum hooperianum, C. pulchellum, and Raphistemma brevipedunculatum, but differs from them by the broadly ovate corolla lobes, purple-red corolla, and connivent corona apex slightly exceeding the corolla throat (Table
Morphological comparison of Cynanchum pingtaoi and closely related species.
Characters | Cynanchum pingtaoi | Cynanchum hooperianum | Cynanchum pulchellum | Cynanchum longhushanense (Raphistemma brevipedunculatum) |
---|---|---|---|---|
Calyx length | ca. 6 mm | 3–4 mm | 3–4 mm | 5–6 mm |
Corolla-tube length | 12–14 mm | 8–9 mm | 12–18 mm | 12–16 mm |
Corolla lobe shape | Broadly ovate (Fig. |
Ovate | Ovate-oblong | Oblong (Fig. |
Corolla color | Outer surface greenish-white, inner surface purple-red (Fig. |
Outer surface light green, inner surface white, with purple spots near the top of corolla lobe | Outer surface slightly greenish, inner surface white | Outer surface greenish-white, inner surface white (Fig. |
Corona-scales apex | Connivent, corona apex slightly exceeding corolla throat (Fig. |
Separate, reaching the middle of the corolla-segments or further | Barely connivent, slightly exceeding corolla throat | Connivent, not exceeding corolla throat (Fig. |
Follicles | Fusiform, with three ribs | Not observed | Oblong, without ribs | Fusiform, with three ribs |
Raphistemma brevipedunculatum is significantly different from Cynanchum hooperianum by the longer calyx lobes (5–6 mm vs. 3–4 mm), the longer corolla-tubes (12–16 mm vs. 8–9 mm), the oblong corolla lobes (vs. ovate), and the corona lobes with connivent corona-scales apex, not exceeding the throat of the corolla (vs. corona-scales apex separate, reaching the middle of the corolla-segments or further). Raphistemma brevipedunculatum flowers in June–July (
The combined phylogenetic analysis shows that the new species forms a monophyletic clade (BS = 100%, Fig.
Simplified maximum likelihood tree of Cynanchum based on two nuclear regions (nrETS and nrITS) and three plastid markers (rps16 and trnL introns, and trnL-F spacer). Bootstrap support values are given for each node. See Suppl. material
≡ Raphistemma brevipedunculatum Y.Wan, in Guihaia 3(3): 197 (1983).
China. Guangxi: Longan County, Longhushan Nature Reserve, open woods, 2 Jul. 1981, D.H. Tan 81329 (holotype: GXSP[GXSP0000038!]; isotype: CANT[CANT00002128!]).
Guangxi Dahuateng (广西大花藤).
Raphistemma brevipedunculatum was considered a synonym of R. hooperianum (
Cynanchum longhushanense G.D.Tang & Miao Liao a flowering branch b cross-section of hollow stem c node with small glands d petiole with glands at the top e inflorescence f bracteoles at the base of the pedicel g flower bud (above: top view; below: side view) h flower (1) top view, (2) lateral view, showing the connivent corona-scales apex, not exceeding the throat of the corolla, (3) side view, showing corolla lobes overlapping to the right and corolla tube i opened corolla, adaxial (above) and abaxial (below) view j ovary with calyx (above: top view, showing glands at the base of the calyx, below: side view of ovary, calyx and pedicel) k ovary l calyx lobes m gynostegium with corona lobes n gynostegium o corona lobes p pollinarium. All photos based on Miao Liao LM78.
China. Guangxi: Longan County, Pingshan Village, 10 Oct. 1977, Longan Investigation Team 2-040 (GXMI[GXMI031735!]); Longan County, Longhushan Nature Reserve, 14 Nov. 1982, Y. Wan & Rui-Ju Liu 82430 (paratype: GXSP[GXSP0000039!]); Longan County, Longhushan Nature Reserve, 25 Jun. 2021, Miao Liao LM78 (IBSC).
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 SJ4825 (holotype, IBSC[IBSC1009908!]; isotypes, IBSC [IBSC1009907!], [IBSC1009909!], [IBSC1009910!]).
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).
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 SJ4825 (IBSC), and drawn by Ding-Han Cui.
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.
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 SJ4825 (IBSC).
The specific epithet pingtaoi honors the eminent botanist Ping-Tao Li (李秉滔), who is an expert in the Apocynaceae.
Bingtao Dahuateng (秉滔大花藤).
Endemic to China. Only one population was found at the border of China-Myanmar in Ruili, Yunnan Province, China. Fig.
Distribution map of Cynanchum pingtaoi and the three Cynanchum species formerly were considered to belong to Raphistemma based on specimens cited in Suppl. material
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.
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).
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 (
This work was supported by the Science and Technology Program from the Forestry Administration of Guangdong Province (2023KJCX001). We are thankful to Prof. Nian-He Xia (South China National Botanical Garden) and Dr. Gang Yao (South China Agricultural University) for their helpful comments and constructive suggestions, and to Guangxi Longhushan Provincial Nature Reserve for supporting our fieldwork, and to the Herbarium of the Guangxi Health Science College (GXSP) for providing the digital specimen images of Cynanchum longhushanense. This paper has been carefully supervised and reviewed by Dr. Guang-Da Tang who was the supervisor of the first author, Miao Liao, but unfortunately passed away on 15 January 2024. We would like to express our deepest remembrance of him here.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This work was supported by the Science and Technology Program from the Forestry Administration of Guangdong Province (2023KJCX001).
Miao Liao: Data curation (Lead); Formal analysis (Lead); Investigation (Supporting); Methodology (Lead); Software (Lead); Validation (Equal); Visualization (Lead); Writing – original draft (Lead); Writing – review & editing (Equal). Si-Jin Zeng: Conceptualization (Supporting); Formal analysis (Equal); Investigation (Lead); Writing – review & editing (Supporting). Lin-Ya Zeng: Investigation (Supporting); Resources (Supporting). Hai-Jun Yin: Investigation (Equal). Mao-Lin Yan: Investigation (Equal). Cai-Fei Zhang: Data curation (Equal); Validation (Equal); Writing – review & editing (Supporting). Guang-Da Tang: Conceptualization (Lead); Data curation (Equal); Formal analysis (Supporting); Funding acquisition (Lead); Methodology (Supporting); Project administration (Lead); Resources (Supporting); Supervision (Lead); Validation (Lead); Writing – review & editing (Lead).
Miao Liao https://orcid.org/0000-0003-2545-9419
Si-Jin Zeng https://orcid.org/0000-0002-3256-0286
Lin-Ya Zeng https://orcid.org/0000-0002-4788-1867
Hai-Jun Yin https://orcid.org/0009-0004-9804-1958
Mao-Lin Yan https://orcid.org/0009-0003-5188-6796
Cai-Fei Zhang https://orcid.org/0000-0002-2818-5751
Guang-Da Tang https://orcid.org/0000-0001-5623-3928
The newly obtained sequences of Cynanchum pingtaoi and C. longhushanense have been submitted to the NCBI website. The DNA sequence data supporting the findings of this study are available in Suppl. material
List of species names changes within Cynanchum in Flora of China
Data type: xlsx
List of ingroup and outgroup taxa used in the phylogenetic analyses
Data type: xlsx
Explanation note: List of ingroup and outgroup taxa used in the phylogenetic analyses with voucher information (geographic origin, collection, herbarium) and Genbank accession numbers. “*” indicates new sequences; “–” indicates missing sequences; bold GenBank accession numbers indicate connected sequences for trnL intron and trnL-F intergenic spacer.
Maximum likelihood tree of Cynanchum
Data type: pdf
Explanation note: Maximum likelihood tree of Cynanchum based on two nuclear regions (nrETS and nrITS) and three plastid markers (rps16 and trnL introns, and trnL-F spacer). Bootstrap support values are given for each node.
Specimens of Cynanchum hooperianum, C. longhushanense, C. pingtaoi, and C. pulchellum used for the distribution map
Data type: docx