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Research Article
Gymnema phuquocense (Apocynaceae, Asclepiadoideae), a new species from Vietnam
expand article infoThu Ha Bui‡, Ngoc Han Le§, The Bach Tran|§
‡ Hanoi National University of Education, Ha Noi, Vietnam
§ Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Ha Noi, Vietnam
| Graduate University of Science and Technology, Ha Noi, Vietnam

Corresponding author: The Bach Tran ( tranthebach.botany@gmail.com )

Academic editor: Andre Simões
© 2025 Thu Ha Bui, Ngoc Han Le, The Bach Tran.
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: Bui TH, Le NH, Tran TB (2025) Gymnema phuquocense (Apocynaceae, Asclepiadoideae), a new species from Vietnam. PhytoKeys 251: 203-210. https://doi.org/10.3897/phytokeys.251.136457
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Abstract

A new species of Gymnema from Vietnam – G. phuquocense – is described, illustrated, and compared with the similar G. yunnanense. Gymnema phuquocense differs from G. yunnanense by the length of peduncle (3–4 mm vs. 10–13 mm), hairs on corolla lobe margin (absent vs. present), shape of seed (broadly ovate vs. ovate-oblong), shape of scale with 2 prominent longitudinal ridges on corolla tube (lanceolate vs. linear), and length of seeds (9–10 mm vs. 13–15 mm). A diagnostic key of the Gymnema species in Vietnam is also provided.

Key words

Asclepiadoideae, Gymnema, Phu Quoc, Vietnam

Introduction

Gymnema R.Br. was established in 1810. The genus comprises approximately 52 species, mainly distributed in tropical or subtropical Asia, S Africa, and Oceania (Li et al. 1995; POWO 2024). Gymnema belongs to Apocynaceae-Asclepiadoideae, and is part of the tribe Marsdenieae (Endress and Bruyns 2000). Since more and more species of Marsdenieae became molecularly analysed, the size of the genus Gymnema has increased, as e.g. many species of the genus Marsdenia (Forster 2021) and Jasminanthes (Liede-Schumann et al. 2022) were transferred to Gymnema. The genus generally consists of lianas, flowers with the corolla tube with 5 scales (5 prominent longitudinal ridges representing corolline corona formings acc. Liede and Kunze 1993), pollinia erect; fruits with a single follicle developing bearing numerous seeds (Li et al. 1995; Tran 2017). In Vietnam, 7 species of Gymnema have been recorded so far (Costantin 1912; Pham 1993; Li et al. 1995; Tran 2005; Tran 2017; POWO 2024).

In March 2022, the authors saw a Gymnema species in An Thoi commune, Phu Quoc district, Kien Giang province in Vietnam. After a literature review as well as comprehensive morphological character analysis, we finally confirmed that the species is new to science and thus describe and illustrate it here.

Materials and methods

The morphology of the new species was observed on both living plants at the field and herbarium specimens. Branches, leaves, flowers and fruits (lf., fl., fr.) of type materials are stored at the Institute of Ecology and Biological Resources (HN) and the Institute of Tropical Biology (VNM) (acronyms follow Thiers 2024). The conservation status of the new species was assessed according to the guidelines of the International Union for Conservation of Nature (IUCN 2019). Other specimens of Gymnema species are studied at HN, VNM and NIMM herbaria that preserved many specimens of species distributed in Vietnam (acronyms follow Thiers 2024).

Taxonomy

Gymnema phuquocense T.B.Tran & T.H.Bui, sp. nov.

urn:lsid:ipni.org:names:77355778-1
Figs 1, 2, 3

Type

Vietnam. • Kien Giang province: Phu Quoc district, An Thoi commune, 28 March 2022, 10°3'32.926"N, 103°59'52.867"E (lf., fl., fr.), Tran The Bach et al. Bach 28032022-1 (holotype: HN80492!; isotypes: HN80493!, HN80494!, HN80495!, HN80496!, VNM00071049!).

Diagnosis

G. phuquocense differs from G. yunnanense by the length of peduncle (3–4 mm vs. 5–6 mm), hairs on corolla lobe margins (absent vs. present), shape of seed (broadly ovate vs. ovate-oblong), and shape of corolline corona scales with 2 prominent longitudinal ridges on corolla tube (lanceolate vs. linear).

Figure 1. 

Gymnema phuquocense T.B.Tran & T.H.Bui A habitat B flowering branch C fruiting branch D leaf, adaxial surface E leaf, abaxial surface F, G, H inflorescence I flower bud J flower (Photos by A.T.Vu, T.B.Tran).

Description

Lianas , 10 m or more. Stem pubescent with white trichomes; internodes 2.5–7.5 cm long. Leaves opposite; petiole 0.5–1.0 cm long, 2.8–3.5 mm diam., pubescent; blade elliptic, 8.8–10.3 cm long, 4.3–6.5 cm wide; adaxial surface glabrous except pubescent nerves, abaxial surface pubescent; base rounded to acuminate; apex acuminate; lateral veins in 4 pairs, retinerved. Inflorescences extra-axillary, 9–10 mm wide, umbelliform, 16–20-flowered; peduncle 3–4 mm long, pubescent. Flowers with buds spherical-elliptic, 2–2.5 mm diam., 3.2–4 mm in diam. when anthetic; pedicel with erect hairs, 1.5 mm long, 0.7–1 mm in diam. Sepals broadly ovate, 1.7–1.8 mm long, ca. 1.4 mm wide; glabrous inside, outside hirsute, margin ciliate, apex rounded, with triangular colleters at the base, 0.34 mm long, 0.23 mm wide;. Corolla campanulate, inside glabrous, outside with sparse hairs; corolla lobes triangular, ca.1.2 mm long, ca.1.3 mm wide, yellowish; corolla tube with 5 prominent longitudinal scales (=corolline corona) in the sinuses of corolla lobes; scales lanceolate with one line of brownish hairs along each side, apex triangular, white, glabrous, .4–1.6 mm long, 0.6–0.7 mm wide, below part of scale rectangular, ca. 1 × 0.5 mm,. Pollinia erect, rectangular-elliptic, 0.31 mm long, 0.13 mm wide; corpusculum rectangle-shaped, 0.16–0.17 mm long, 0.06–0.07 mm wide; caudicles 0.02 mm long, 0.05 mm wide. Style head hemispherical, 0.8–0.9 mm high, 1.2–1.3 mm wide. Ovary bi-carpellate. Follicle 1, developed from only one of the two carpels, lanceolate, 5–6 cm long, 2.2–2.5 cm wide; outside pubescent; pericarp 0.9–1.1 mm thick; mature fruits yellow. Seeds numerous, ca. 60 per follicle; seeds flattened, broadly ovate, 9–10 mm long, 5–6 mm wide, comma 25–30 mm long, white.

Figure 2. 

Gymnema phuquocense T.B.Tran & T.H.Bui A, B corolla C gynostegium D pollinarium E, F fruit G, H, I seeds (Photos by A.T.Vu, T.B.Tran).

Etymology

The specific epithet refers to the type locality, Phu Quoc district in Vietnam.

Distribution and ecology

Gymnema phuquocense was found growing in bright places at the secondary forest of Phu Quoc district, in association with Acacia auriculiformis A.Cunn. ex Benth., Chromolaena odorata (L.) R.M.King & H.Rob., Micromelum minutum (G.Forst.) Wight & Arn., Mimosa pudica L., Parinari annamensis Hance, Psychotria asiatica L., Sida rhombifolia L., Stachytarpheta jamaicensis (L.) Vahl, Streptocaulon juventas (Lour.) Merr.,and Tetracera scandens (L.) Merr.. Flowering and fruiting were observed in March-April.

Figure 3. 

Gymnema phuquocense T.B.Tran & T.H.Bui A fruiting branch B flowering branch C, D, E leaf, adaxial surface F, G, H leaf, abaxial surface I, J inflorescence K calyx L corolla M 5 scales on corolla N gynostegium O, P pollinarium Q, R fruit S seed (Drawn by Le Kim Chi).

Conservation status

Known from only one locality; the preliminary conservation status of Gymnema phuquocense is Data Deficient (DD; IUCN 2019). More fieldwork still need to be done in order to get a better understanding of the full natural distribution of this taxon.

Discussion

The differences between Gymnema phuquocense and G. yunnanense are clear (Table 1). G. yunnanense is widely distributed on the mainland from SE. Bangladesh to China (S. Yunnan, SW. Guangxi) and Vietnam (Kon Tum province, Kien Giang province: Ha Tien) (Tran 2017, POWO 2024) while G. phuquocense is only found on Phu Quoc island (Kien Giang province). However, Gymnema species, especially of the G. sylvestre group to which the new species belong, are difficult to distinguish. The G. sylvestre group includes G. muelleri Benth. (Northern Territory, Queensland), G. tricholepis Schltr. (New Caledonia, New Guinea, Queensland), G. stramineum (P.I.Forst.) P.I.Forst. (Queensland), G. sylvestre (Retz.) R.Br. ex Sm. (Tropical & Subtropical Old World), G. pachyglossum Schltr. (Philippines), G. maingayi Hook.f. (Malaya, Myanmar, Thailand), G. latifolium Wall. ex Wight (India to S. China and and Indo-China) and G. longipedicellatum (P.I.Forst.) P.I.Forst. (Queensland) (Liede-Schumann et al. 2022, POWO 2024). Another species belonging to this group is G. thorelii recorded in Laos, G. thorelii (Costantin 1912; POWO 2024), also has many similar characteristics. However, G. phuquocense differs from G. thorelii by the leaf size (8.8–10.3 × 4.3–6.5 vs. 5–6 × 2.8–3.3), leaf surface (pubescent vs. glabrous), flower diameter (3.2–4 mm vs. 2.5 mm) and the indument of corolla lobe margins (without hairs vs. with hairs). G. phuquocense differs from other species of Gymnema by the following set of characteristics: peduncle 3–4 mm long, corolla tube hairy but corolla lobe margins not cilliate and not purple, corolline corona scales higher than tube, follicles shorter than 4 cm and seeds broadly ovate, 9–10 mm long.

Table 1.
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Morphological differences between G. phuquocense and G. yunnanense.

Characters G. yunnanense G. phuquocense
Number of lateral veins (pairs) 5–6 4
Length of peduncle (mm) 10–13 3–4
Corolla lobes Ciliate not ciliate
Shape of corolline corona Linear Lanceolate
Shape of seed ovate-oblong broadly ovate
Length of seed (mm) 13–15 9–10

Key to the species of Gymnema in Vietnam

1 Corolla (excluding “corolline corona”) glabrous 2
– Corolla (excluding “corolline corona”) hairy 3
2 Seeds 12.5–14 × 8–9 mm G. acuminatum
– Seeds ca. 8 × 4 mm G. sylvestre
3 Corolla margins purple; fruit 4–6 cm wide G. griffithii
– Corolla margins white or yellow; fruit less than 4 cm wide 4
4 Corolline corona scales shorter than tube 5
– Corolline corona scales longer than tube 7
5 Corolla lobes densely pubescent inside G. latifolium
– Corolla lobes glabrous inside 6
6 Petiole 2–6 cm long; seeds ca. 1.5 × 1 cm, comma ca. 4 cm long G. inodorum
– Petiole 0.5–1 cm long; seeds ca.1.4 × 0.6 cm, comma ca. 3 cm long G. foetidum
7 Peduncle 10–13 mm long; corolla lobes cilliate; seeds ovate-oblong, 13–15 mm long G. yunnanense
– Peduncle 3–4 mm long; corolla lobes not cilliate; seeds broadly ovate, 9–10 mm long G. phuquocense

Additional specimens examined

G. acuminatum: Vietnam. Dong Nai: Trang Bom, 28 May 1919, Poilane 40886 (VNM); G. foetidum: Vietnam, Dak Lak: Krong Pac, 1 June 1979, N. T. Ban, Ban 365 (HN); G. griffithii: Vietnam. Dak Lak: Ea H’leo, Ea Sol, 8 August 2011, Tran The Bach, VK 4676 (HN); G. inodorum: Vietnam. Hoa Binh, Do Dang Ly 584A, 584B, 584BC, 584D (NIMM); G. latifolium: Vietnam. Ninh Binh: Cuc Phuong, NMC 1194, MVX 151, NMC 1321, MVX 658 (HN) – Quang Tri: Huong Hoa, 16 March 2014, Tran The Bach, VK 5880 (HN) – Thanh Hoa, 15 October 1997, VN 305 (HN); G. sylvestre: Vietnam. Bac Giang, 6 November 1940, Petelot 2435 (VNM) – Ninh Thuan: Phan Rang, 2 March 1924, Poilane 9856 (VNM), 4 March 1923, Poilane 5563 (VNM)– Quang Ninh, 22 August 2002, V. X. Phuong 5406 (HN); 22 August 2002, V.X. Phuong 5479 (HN); 22 August 2002, V.X. Phuong 5482 (HN); 22 August 2002, V.X. Phuong 5510 (HN); Tien 213 (HN) – Quang Tri: Gio Linh, 13 May 2007, Tran The Bach, VK 1060 (HN) – Vinh Phuc, V. X. Phuong 1061 (HN), T. D. Ly 217 (HN) – Thua Thien Hue: Lang Co, 199 (VNM); G. yunnanense: Vietnam. Kien Giang, V. X. Phuong 10124 (HN) – Kon Tum: Dak Glei, VH 1418, (HN), 2 April 2009, Tran The Bach, VK 2593 (HN).

Acknowledgements

We thank the curator of the herbarium HN, VNM, NIMM for access to herbarium specimens, Dr. Michele Rodda for advising the identification, Le Kim Chi for preparing the drawing and Vu Anh Thuong for investigation. Funding for this research was provided by the project ĐTĐL.CN-72/22.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Funding

Funding for this research was provided by the project ĐTĐL.CN-72/22.

Author contributions

Thu Ha Bui: Identification, description, key establishing and manuscript writing. Ngoc Han Le: Study on specimens at HN herbarium and related references. The Bach Tran: Investigation, identification, description, key establishing and manuscript correction.

Author ORCIDs

Thu Ha Bui https://orcid.org/0000-0001-6971-0105

Ngoc Han Le https://orcid.org/0000-0003-2657-5091

The Bach Tran https://orcid.org/0000-0003-3798-5969

Data availability

All of the data that support the findings of this study are available in the main text.

References

  • Costantin J (1912) Asclépiadacées. Flore Générale de L’Indo-Chine 4(1). Masson et Cie, Paris, 1–154.
  • Forster PI (2021) Gymnema R. Br. and Leichhardtia R. Br.(Apocynaceae), reinstated genera for taxa previously included in Marsdenia R. Br.: A conspectus for Australia, New Guinea and the Solomon Islands. Austrobaileya 11: 1–18. https://doi.org/10.5962/p.366373
  • Li PT, Gilbert MG, Stevens WD (1995) Asclepiadaceae. Flora of China 16. Sci. Press, Beijing & Missouri Bot. Garden Press, St. Louis, 189–270.
  • Liede S, Kunze H (1993) A descriptive system for corona analysis in Asclepiadaceae and Periplocaceae. Plant Systematics and Evolution 185(3–4): 275–284. https://doi.org/10.1007/BF00937663
  • Liede-Schumann S, Reuss SJ, Meve U, Gâteblé G, Livshultz T, Forster PI, Wanntorp L, Rodda M (2022) Phylogeny of Marsdenieae (Apocynaceae, Asclepiadoideae) based on chloroplast and nuclear loci, with a conspectus of the genera. Taxon 71(4): 833–875. https://doi.org/10.1002/tax.12713
  • Pham HH (1993) Cay co Viet Nam: An illustrated flora of Vietnam 2(2). Mekong Printing, Montreal, 910–949.
  • Thiers B (2024) Index Herbariorum: A global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. http://sweetgum.nybg.org/ science/ [Retrieved 01 August 2024]
  • Tran TB (2005) Asclepiadaceae. Checklist of plant species of Vietnam 3. Vietnamese Acad. Sci. Technol., Missouri Bot. Garden & Hanoi Nat. Univ., Agric. Publ. House, Hanoi, 58–75.
  • Tran TB (2017) Publishing House for Science and Technology, Hanoi. Flora of Vietnam 15: 178–190.
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