Lithocarpus hongiaoensis Ngoc & Binh, 2021

Ngoc, Nguyen Van, Binh, Hoang Thi, Nagahama, Ai, Tagane, Shuichiro, Toyama, Hironori, Matsuo, Ayumi, Suyama, Yoshihisa & Yahara, Tetsukazu, 2021, Morphological and molecular evidence reveals three new species of Lithocarpus (Fagaceae) from Bidoup-Nui Ba National Park, Vietnam, PhytoKeys 186, pp. 73-92 : 73

Lithocarpus hongiaoensis Ngoc & Binh sp. nov.

Fig. 5

Type.

Vietnam. Lam Dong Province, Bidoup-Nui Ba National Park, Hon Giao , at edge of evergreen forest, roadside, 1580 m elev., 12°10'35.9"N, 108°42'25.1"E, 19 June 2015, N. Nguyen, D. Luong, B. Hoang V3235 [young male fl. and fruits] (holotype DLU!; isotypes FU!, HN!, KYO!, VNM!) .

Diagnosis.

Lithocarpus hongiaoensis is similar to L. vinhensis but differs in having much longer petioles, fewer secondary veins, longer infructescences, bigger cupules, and bigger nuts. It is also similar to L. vuquangensis but differs in having much longer petioles, more secondary veins, longer infructescences, and bigger cupules (Table 2 ).

Description.

Evergreen tree, up to 25 m tall. Twigs blackish gray, glabrescent, densely lenticellate. Stipules narrowly triangular, ca. 5 × 1 mm, densely covered with indumentum abaxially, almost glabrous adaxially. Leaves alternate; petioles 1.7-3.5 cm long, glabrous; blades narrowly elliptic to lanceolate, 7.6-14.7 × 2.3-4.6 cm, coriaceous, glabrous adaxially, covered with adherent waxy scales abaxially, apex acuminate, acumen up to 1.5 cm long, base attenuate and decurrent on petiole, margin entire, midrib flat or slightly prominent near base adaxially, prominent abaxially, greenish yellow in vivo, reddish brown in sicco; secondary veins 8-11 pairs, prominent abaxially, at an angle of 35-45° from the midrib, tertiary veins scalariform, faintly visible or invisible on both sides. Young male inflorescences terminal, ca. 5-7 cm long, densely covered with white indumentum. Infructescences terminal, erect, 12.5-16.5 cm long, rachis 0.4-0.6 cm thick at base, grayish brown, lenticellate, covered with indumentum. Cupules solitary, sessile, obconical to saucer-shaped, 0.8-1.2 cm high, 1.7-2.6 cm in diam., enclosing 1/3-1/2 of the nut; wall woody, ca. 2 mm thick, with triangular scales not united into concentric rings; scales up to 4 mm long, apex shortly acuminate, covered with dense grayish indumentum outside. Nut strongly depressed ovoid, 0.6-1.1 cm high, 1.2-1.5 cm in diam., glabrous, reddish brown to grayish brown in sicco, tomentose with soft white hairs near apex; basal scar slightly concave, 1.2-1.4 cm in diam.

Phenology.

Young male flowers and mature fruits were collected in May and June.

Distribution.

Vietnam (so far known only from Hon Giao area of Bidoup-Nui Ba National Park, Lam Dong Province). (Fig. 1 ).

Etymology.

The specific epithet is derived from the type locality, Hon Giao area of Bidoup-Nui Ba National Park, Lam Dong Province, Vietnam.

Local name.

Dé đá Hòn Giao.

Conservation status.

The new species is narrowly endemic to Hon Giao area of Bidoup-Nui Ba National Park, Lam Dong Province. During our floristic expedition from 2015 to present, we found only five mature individuals of Lithocarpus hongiaoensis at the road in montane evergreen forest which is located within the protected area of the national park. According to criterion D of the IUCN Red List criteria ( IUCN 2012), this species is qualified as CR.

Additional specimens examined.

Vietnam. Lam Dong Province: Bidoup-Nui Ba National Park, Hon Giao , 1574 m elev., 12°10'34.5"N, 108°42'25.5"E, 15 May 2019, N.V. Ngoc, H.T. Binh, N.V. Duy, T.T. Nhung NAF122 [fr.] (DLU!); ibid., 1574 m elev., 12°10'35.5"N, 108°42'25.9"E, 11 June 2020, N.V. Ngoc, H.T. Binh, N.V. Duy, T.T. Nhung NAF192 [fr.] (DLU!) .

Figures

Figure 1. Type locality of the new species (Black dots): L 1: L. bidoupensis, L 2: L. congtroiensis, and L 3: L. hongiaoensis.

Figure 5. Lithocarpus hongiaoensis Ngoc & Binh A habit B twig with young inflorescences C leaves D young male inflorescence E infructescence F inside of mature cupule.