Quercus xuanlienensis Binh, Ngoc & Bon, 2018

Binh, Hoang Thi, Ngoc, Nguyen Van, Bon, Trinh Ngoc, Tagane, Shuichiro, Suyama, Yoshihisa & Yahara, Tetsukazu, 2018, A new species and two new records of Quercus (Fagaceae) from northern Vietnam, PhytoKeys 92, pp. 1-15 : 9-10

Quercus xuanlienensis Binh, Ngoc & Bon sp. nov. Fig. 3

Diagnosis.

Quercus xuanlienensis is morphologically similar to Q. edithiae of China and Vietnam in leaf size (7-15 × 3-5.8 cm), cuneate leaf base, petiole length (1.5-2.8 cm long), number of secondary veins (8-11 pairs), bowl-shaped cupule, ellipsoid to cylindrical-ellipsoid nut and basally convex nut but differs in leaf margin serrulate only at apical 1/5-1/7 (vs. serrate in the upper 2/3), entire bracts of cupule (vs. almost denticulate except basal 2 or 3 rings which is entire), cupule enclosing 1/5 of the nut (vs. enclosing 1/4-1/3 of the nut) and longer nut (5-6 cm long vs. 4-4.5 cm long).

Type.

VIETNAM. Thanh Hoa Province, Thuong Xuan District, Xuan Lien Nature Reserve , in evergreen forest around waterfall, alt. 810 m, 19°52'46.7"N, 105°11'34.4"E, 6 Mar. 2017, Binh HT, Ngoc NV, Bon TN V6967 (holotype KYO!; isotypes DLU!, FU!, P!, VNM!) .

Description.

Tree, ca. 18 m tall. Buds ellipsoid, ca. 9 mm long, ca. 4 mm in diam., scales imbricate, in 4-5 rows, ovate-triangular, ca. 3 × 2.5 mm, apex obtuse, margin ciliate, appressed whitish to yellowish brown hairy on both surfaces. Twigs glabrous when old, lenticellate. Stipules linear-lanceolate, 10-14 mm long, densely appressed hairy, glabrescent outside, glabrous inside. Leaves alternate; blade leathery, oblong-elliptic or obovate, (6-)8-11(-15) × 3-4.5(-5) cm, apex acuminate, acumen up to 0.6 cm long, base cuneate, margin recurved, serrulate in the upper 1/5-1/7, pale brown on the upper surface, yellowish brown to reddish brown on the lower surface when dry, glabrous on both surfaces; midribs ± flat on upper surface, prominent and distinct on lower surface, lateral veins 8-11 pairs, prominent on lower surface, at an angle of 40-45 degrees from midrib, straight and running into the margin, tertiary veins scalariform, indistinct on upper surface, prominent and distinct on lower surface; petioles 1-2 cm long, glabrous. Male and female inflorescences not seen. Infructescences axillary or terminal, erect, rachis 8-10 mm long, 4-5 mm in diam., glabrous, brownish red when fresh, blackish when dried. Fruits 6-6.5 cm high (including cupule), solitary or twin, sessile; cupules bowl-shaped, 1.3-1.7 cm high, 1.9-2.1 cm in diam., enclosing ca. 1/5 of the nut when mature, outside whitish to yellowish brown tomentose to glabrous, inside densely appressed yellowish brown hairy, wall ca. 1-2 mm thick, comprising of bracts, bracts arranged in 7-8 rings, margin of rings entire; nuts ellipsoid to cylindrical-ellipsoid, 5-6 cm high, 2-2.3 cm in diam., apex acute, densely appressed yellowish brown hairy around stylopodia, with stylopodia up to 4 mm long, basal scar 9-10 mm in diam., convex, to 3 mm high, glabrous.

Distribution.

Vietnam. Thanh Hoa Province, Thuong Xuan District, Xuan Lien Nature Reserve.

Ecology in Vietnam.

At present, only one individual was found in evergreen forest, at 810 m altitude.

Etymology.

The specific epithet is derived from the district name of the type locality, Xuan Lien Nature Reserve, Thuong Xuan District, Thanh Hoa Province, North Central Coast of Vietnam.

Phenology.

Fruiting specimens were collected in March.

GenBank accession no.

Binh et al. V6967: LC331257 (rbcL), LC331254 (matK).

Preliminary conservation status.

Quercus xuanlienensis is known for only one individual inside the protected area of Xuan Lien Nature Reserve. According to the criterion D of the IUCN Red List criteria ( IUCN 2012), this species is qualified as Critically Endangered (CR).

Figures

Figure 3. Quercus xuanlienensis Binh, Ngoc & Bon. A Leafy twig B Adaxial side of mature leaf C Stipules D Bud E, F Inside and outside of bud scale G Mature fruit H, I Inside and outside of cupule J Basal scar of the nut. Scale bars: C 5 mm D 3 mm. Materials from Binh et al. V 6967.