Lithocarpus vuquangensis Ngoc & Hung, 2018

Nguyen Van, Ngoc, Nguyen Viet, Hung, Hoang Thi, Binh, Tagane, Shuichiro, Toyama, Hironori, Son, Hoang Thanh, Tran Viet, Ha & Yahara, Tetsukazu, 2018, Lithocarpus vuquangensis (Fagaceae), a new species from Vu Quang National Park, Vietnam, PhytoKeys 95, pp. 15-25 : 21-22

Lithocarpus vuquangensis Ngoc & Hung sp. nov. Figure 3

Diagnosis.

Similar to Lithocarpus nantoensis , L. hongiaoensis and L. vinhensis , but distinguished from L. nantoensis mainly by its fewer secondary veins, shorter infructescences, longer fruiting stalk, larger nut size and larger scar size of the nut, from L. hongiaoensis by its much shorter petioles and infructescences, longer fruiting stalk, scales united into concentric rings and much larger nut size and from L. vinhensis by having fewer secondary veins, shorter infructescences and much larger nut size (Table 2 ).

Type.

VIETNAM. Ha Tinh Province, Vu Quang National Park, in lower montane forest, along trail to the summit of Mt. Rao Co , alt. 1518 m, 18°12'12.2"N, 105°23'15.3"E, 22 June 2016, Yahara T., Nguyen Van Ngoc, Toyama H., Tagane S., Okabe N., Nguyen Viet Hung V 5743 (holotype: KYO!; isotypes: DLU!, FU!, HN!, K!, P!, VNM!) .

Description.

Trees, to 20 m tall; young branches mostly glabrous, yellowish in vivo, reddish-brown in sicco. Leaves alternate, spirally arranged, blade narrowly elliptic to lanceolate, 7.5-11 × 2.3-3.6 cm, crunchy, glabrous adaxially, white farinose abaxially, apex long acuminate, acumen up to 1.2 cm long, base cuneate to attenuate, margin entire and wavy; midrib flat or slightly prominent near base adaxially, prominent abaxially, greenish-yellow in vivo, reddish-brown in sicco, secondary veins 7-10 pairs, at an angle of 40-50 degrees from the midrib, prominent abaxially, tertiary veins scalariform, faintly visible to invisible on both sides; petiole 1-1.5 cm long, glabrous, terete. Male inflorescence a spike, 7-8.5 cm long. Male flower solitary; calyx 6-lobed, lobes ovate, 0.5-0.6 mm × 0.4-0.5 mm, pubescent on both surfaces; stamens 12, 0.7-0.9 mm long, anthers 0.1-0.15 mm long. Infructescences erect, woody spike, up to 7 cm long, axis ca. 2 mm thick at base, greyish-brown, lenticellate. Cupule solitary, broadly obconical to saucer-shaped, 1.4 cm long, 1.8 cm in diam., enclosing only basal to 1/4 of the nuts; scales triangular, arranged into 4-5 concentric rings, apex shortly acuminate, densely covered with tawny minute hairs; fruiting stalk ca. 4-6 mm long, 4-7 mm in diam. Nut obovoid or globose, 1.7-2.0 cm long, 2.1-2.4 cm in diam., glabrous, dehiscent; basal scar concave, ca. 1.1 cm in diam.

Phenology.

Mature fruits were collected in June.

Distribution.

Vietnam (so far known only from Vu Quang National Park, Ha Tinh Province) (Figure 1 ).

Etymology.

The specific epithet is derived from its type locality, Vu Quang National Park.

GenBank accession No.

Yahara et al. V5743: LC319671 (rbcL), LC319670 (matK), KY786083 (ITS).

Preliminary conservation status.

Critically Endangered (CR). In the field observation, less than 10 individuals were found along the trail to the summit of Mt. Rào Cô, in lower montane forest. The habitat is inside the protected areas of Vu Quang National Park, but based on criterion D of the IUCN Red List criteria ( IUCN 2012), this species is qualified as CR. Further intensive inventories are needed to find additional populations in Vu Quang National Park and its surrounding areas.

Figures

Figure 1. Location of Vu Quang National Park (Black triangle), type locality of Lithocarpus vuquangensis.

Figure 3. Lithocarpus vuquangensis Ngoc & Hung: A Branch with male inflorescences B Lower leaf surface C Holotype (KYO) D Spike with cupule E Young acorn F-H Side view, top view and scar of the mature nut, respectively I A part of infructescence K, L Inside and outside of the cupule. C, D, F-L From Yahara et al. V 5743. Scale bars: 2 cm (D), 1 cm (F-H, K, L).