Gymnema phuquocense T. B. Tran & T. H. Bui, 2025

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

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 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: HN 80492 !; isotypes: HN 80493 !, HN 80494 !, HN 80495 !, HN 80496 !, VNM 00071049 View Materials !) GoogleMaps .

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).

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.

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.

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 View 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.

Key to the species of Gymnema in Vietnam

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 584 A, 584 B, 584 BC, 584 D ( 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).