Glycosmis quangtriensis T.A.Le & Tagane

Le, Tuan Anh & Tagane, Shuichiro, 2024, Glycomis quangtriensis (Rutaceae), a new species from Quang Tri province, central Vietnam, Phytotaxa 650 (1), pp. 116-120 : 117-119

Glycosmis quangtriensis T.A.Le & Tagane , sp. nov. ( Fig. 2 )

TYPE:— VIETNAM. Quang Tri Province, Cam Lo District, Cam Tuyen Commune , Razorback Hill , 16°48′12.7″N, 106°50′04.6″E, ca. 280 m a.s.l., 18 March 2023, Tuan Anh Le LTA 998 (holotype VNMN!, isotype SGN!).

Diagnosis. Glycosmis quangtriensis is characterized by shrub habit 1.5 m tall, subsessile and simple leaves which blade is elliptic-oblong or narrowly elliptic-oblong with strongly cordate to auriculate base, 3–4-flowered condensed raceme, 10–12 stamens arranged in two whorls, and subglobose fruits 12.5–13 × 11–11.5 mm, by which combination it is clearly distinguished from all the previously known species in the genus.

Shrubs to 1.5 m tall, young branches densely covered with rust-colored indumentum, old blanches glabrescent. Bark corky, almost glabrous, with longitudinal cracks, cracked parts whitish brown to greyish brown. Leaves alternate, subsessile, simple, emitting a aromatic odor resembling citrus scent when bruised; blades elliptic-oblong, or rarely narrowly elliptic-oblong, 8.8–9.2 cm long, 2.9–3.2 cm wide, coriaceous, adaxial side lustrous, dark green, abaxial side pale green, with pellucid gland dots, both surfaces densely covered with rust-colored indumentum when young, glabrous except midrib when old, base strongly cordate to auriculate, apex caudate to acuminate, margin entire, undulate, midrib raised on both surfaces, pubescent, secondary veins 10–12 pairs, brochidodromous, slightly prominent abaxially, tertiary veins finely reticulate, faintly visible on both surfaces. Inflorescence axillary, 3–4-flowered, condensed racemose; peduncle very short, 0.2–1 mm long, densely rusty tomentose. Flowers bisexual, 5-merous; pedicel sessile to 1 mm long, densely covered with rust-coloured indumentum. Sepals ovate-triangular, 2–2.1 mm long, 1.8–2 mm wide, greenish-white, glabrous on both surfaces, densely covered with pellucid gland dots abaxially, apex obtuse. Petals elliptic, 3.5–4 mm long, 1.5–2 mm wide, glabrous adaxially, puberulent with yellowish hairs abaxially, apex obtuse. Stamens 10–12 in two whorls of 5–6 each, incurved, shorter ones antepetalous, 2.0– 2.8 mm long; anthers dorsifixed, 0.6–0.9 mm long, glabrous, filaments 1.4–1.9 mm long, glabrous. Pistil 2.9–3 mm long; gynophore swollen, broader than ovary; ovary 3-locular, densely covered with white hairs and gland dots; style short and attenuate, densely covered with gland dots; stigma obtuse, not enlarged, dark brown. Fruits subglobose, 12.5–13.0 mm long, 11–11.5 mm in diam., green when young, light pink when ripen, puberulent, pistil persistent. Seeds 1, subglobose, 9.0– 9.5 mm long, 7.5–8 mm in diam., glabrous, greenish, with membranous seed coat.

Distribution:— Vietnam, Quang Tri Province (so far known only from the type locality) ( Fig. 1 ).

Habitat and ecology:— Glycosmis quangtriensis grows in broad-leaved semi-evergreen forest on limestone hill at 280 m a.s.l., where it grows with Aspidistra sarcantha Aver., Tillich, T.A.Le & K.S.Nguyen ( Asparagaceae ), Trigonostemon eberhardtii Gagnep. ( Euphorbiaceae ), Gymnosporia diversifolia Maxim. ( Celastraceae ) and Gynostemma pentaphyllum (Thunb.) Makino ( Cucurbitaceae ). Flowering from February to July. Fruiting from May to August.

Etymology:— The specific epithet is derived from the name of the province name where the type was collected, Quang Tri Province.

Vernacular name:— CƠm rƯỢu quảng trị (proposed here). “CƠm rƯỢu” is the general name for Glycosmis in Vietnam, and “quảng tri” is the province where the species was found.

Preliminary conservation assessment:— Critically Endangered (CR). Glycosmis quangtriensis is known only from type locality with fewer than 50 mature individuals in broad-leaved semi-evergreen forest on limestone karst in Cam Lo district, Quang Tri province, central Vietnam. Although the first author carried out more than 20 field surveys in limestone areas in Quang Tri province including its type locality in 2021–2023, no additional populations and individuals were found. The Extent of Occurrence (EOO) of this species is estimated to 2.3 km 2: the area of the Razorback Hill with 1.9 km 2 and Rockpile with 0.4 km 2, both of which are limestone karst in the area. The species is considered to be threatened by limestone mining and deforestation. Given this situation, it is assessed as Critically Endangered following the criteria B2a + b(iii), D ( IUCN 2022). To date, we surveyed 40% of the total areas in the district and further field studies are needed to more accurately determine the distribution range and population size.

Note:— Glycosmis quangtriensis is characterized by sessile, simple, and elliptic-oblong lamina with undulate margins and an auriculate base. In Vietnam, it might be most similar to G. petelotii Guillaumin (1944: 216) in having sessile and simple lamina and condensed racemes, but easily distinguished from G. petelotii by having alternate leaves, cordate to auriculate lamina base and larger petals that are 3.5–4 mm long (vs. leaves mostly subopposite, lamina base obtuse to rounded and petals 2.5 mm long in G. petelotii ).

Additional specimen examined: — VIETNAM. Quang Tri Province: Cam Lo District, Cam Tuyen Commune, Rockpile Hill , 16°46′72.7″N 106°51′16.1″E, ca. 150 m a.s.l., 10 July 2022, Tuan Anh Le LTA 976 (VNMN!) ; Dakrong District, Huong Hiep Commune, Razorback , 16°47′34.3″N, 106°50′50.17″E, ca. 190 m a.s.l., 10 July 2022, Tuan Anh Le LTA 377 ( KAG [ KAG 185305!], SGN, VNMN) .

Figures

FIGURE 1. Distribution of Glycosmis quangtriensis T.A. Le & Tagane (closed triangle).

FIGURE 2. Glycosmis quangtriensis T.A. Le & Tagane, sp. nov.A. Flowering branch. B. Bark. C. Cross section of stem, D. Flowers. E. Stamens.F. Petals (upper: abaxial side, lower: adaxial side), G. Pistils, some calyx removed. H.Young fruits (above), mature fruit (below), I. Seed. Photos by L.T. Anh.