Quercus ngochoaensis Binh & Son, 2021

Binh, Hoang Thi, Ngoc, Nguyen Van, Son, Hoang Thanh, Tagane, Shuichiro & Yahara, Tetsukazu, 2021, Quercus ngochoaensis (Fagaceae), a new species from Ba Vi National Park, northern, Vietnam, Phytotaxa 516 (3), pp. 283-288 : 284-285

Quercus ngochoaensis Binh & Son , sp. nov. Figure. 1

Type: — VIETNAM. Ha Noi Capital, Ba Vi National Park, edge of Ngoc Hoa moutain, in evergreen forest, 21°04′8.9″N 105°21′28.2″E, 1100 m elev., 19 November 2017, N. Nguyen, B. Hoang, Son H. V 7499 (holotype DLU!; isotypes, HN!, VAFS!, VNM!) .

Diagnosis.— Quercus ngochoaensis is similar to Q. glauca Thunb. (1784: 858) in having glabrous twigs, cuneate leaf base, two or three fruits per infructescence, almost entire margin of the lamellate ring on a cupule, and slightly convex scar at the base of a nut, but distinguished by smaller leaves, shorter petioles 1.1–1.5 cm long (vs. 1–3 cm long), leaf margin serrate in the upper (4/5–)2/3 (vs. remotely serrate in the upper 1/2), cup-shaped cupule (vs. bowl-shaped), cupule enclosing 1/2–2/3 of the nut (vs. enclosing 1/3–1/2 of the nut), bracts of cupule arranged in 7–8 rings (vs. 5–6 rings), and subglobose nut (vs. ovoid, oblong-ovoid or ellipsoid nut) ( Table 2).

Tree, 5–7 m tall, 15 cm girth. Bark whitish gray. Buds perulate, oblong to ellipsoid, 1–3 mm long, 0.5–1 mm in diam., bud scales imbricate, in 4–6 rows, ovate-triangular, ca. 1 × 1.5 mm, apex obtuse, margin ciliate, covered with appressed, whitish to yellowish brown hair on both surfaces. Twigs dark pale green, glabrous, lenticellate. Leave alternate; blade thinly leathery, ovate or ovate-elliptic, 4.5–7.5 × 2.1–3.2 cm, acuminate at apex, broadly cuneate at base, margin serrate in the upper (4/5–)2/3, having 5–7 teeth per side, conspicuously pale creamy brown to dark brown when dry, glabrous on both surfaces, midrib slightly raised on upper surface, prominently raised on lower surface, lateral veins 7–10 pairs, prominent on lower surface, at angle of 45–55(–60) degree from midrib, straight and then curved near margin and running into the teeth of the margin, tertiary veins scalariform, faintly visible on lower surface; petioles 1.1–1.5 cm long, white tomentose when young, glabrescent. Male and female inflorescences not seen. Infructescences axillary, erect, peduncle 1.5–2.5 cm long, rachis 0.6–0.9 cm long, 0.9–1.2 mm in diam., woody, glabrous, dark yellow-green when fresh, blackish brown when dried, lenticellate. Fruits 1.5–2.1 cm high (including cupule), solitary, sessile on woody rachis; nuts subglobose, 0.9–1.2 cm high, 0.8–1.2 cm in diam., slightly depressed and concave at top, densely white tomentose outside, more densely around stylopodia, stylopodia 1.1–1.2 mm long, basal scar 7–9 mm in diam., slightly convex; cupules cup–shaped, 0.8–1.1 cm high, 1.2–1.4 cm in diam., enclosing 1/2 to 2/3 of the nut when mature, outside densely covered with white hairs, inside villous with appressed white hairs, wall ca. 0.5 mm thick, lamellate bracts arranged in 7–8 rings, margin of the rings almost entire except in the lowest three rings which are distinctly toothed.

Additional specimens examined: — VIETNAM. Ha Noi Capital, Ba Vi National Park , 21°4′8.5″N 105°21′28.7″E, 1100 m elev., 24 March 2020, N. Nguyen, B. Hoang QC131 [ster.] ( DLU!) .

Distribution:— Vietnam (so far known only from the type locality, Mt. Ngoc Hoa of Ba Vi National Park)

Habitat and Ecology:— The species was collected in evergreen broad-leaved forest mixed with conifers on limestone rocky mountain at elevations 1100 m. The forest composed Calocedrus macrolepis Kurz (1873: 196) (Cupressaceae) , Podocarpus neriifolius D. Don (1824: 21) (Podocarpaceae) , Quercus macrocalyx Hickel & A. Camus (1921: 383) , Castanopsis chinensis ( Sprengel 1826: 856) Hance (1869: 201) (Fagaceae) , Camellia caudata Wallich (1832: 36) (Theaceae) , and Neolitsea sp. (Lauraceae) .

Phenology:— Fruiting specimens were collected in November.

Etymology:— The specific epithet is derived from its type locality, Ngoc Hoa mountain belonging to Ba Vi National Park, Ba Vi District, Ha Noi Capital, Vietnam.

Vernacular name: Sồi Ngọc Hoa

GenBank accession No.— Binh et al. V7499: LC536642 (mat K) , LC536643 (rbc L) , MT274524 (ITS) .

Primary conservation assessment:— Critically Endangered (CR). At present we found only 20 reproductively mature trees in Ba Vi National Park, at the altitude of 1100 m. Therefore, this species is qualified as CR under criterion D according to IUCN Red List criteria ( IUCN Standards and Petitions Subcommittee, 2019).

Figures

FIGURE 1. Quercus ngochoaensis Binh & Son. A. Fruiting branches and buds, B. Abaxial surface of mature leaf, C. Infructescence, D. Nut (lateral view), E. Nut (top view), F. Basal scar of the nut, G. Side view of the cupule, H. Inside of cupule. Materials: A–H from Binh et al. V7499.