Lithocarpus dahuoaiensis Ngoc & L. V. Dung, 2016

Ngoc, Nguyen Van, Dung, Luong Van, Tagane, Shuichiro, Binh, Hoang Thi, Son, Hoang Thanh, Trung, Vo Quang & Yahara, Tetsukazu, 2016, Lithocarpus dahuoaiensis (Fagaceae), a new species from Lam Dong Province, Vietnam, PhytoKeys 69, pp. 23-30 : 24-26

Lithocarpus dahuoaiensis Ngoc & L. V. Dung sp. nov. Figs 2 , 3

Diagnosis.

Lithocarpus dahuoaiensis is morphologically similar to Lithocarpus macphailii (M.R.Hend.) Barnett and Lithocarpus encleisocarpus (Korth.) A. Camus in having a completely entire leaf margin, solitary cupule, long stalks of fruits, deeply cup-shaped or turbinate cupules with the number of horizontal filiform lines. But Lithocarpus dahuoaiensis is distinct by its cupules enclosing ca. 1/2-2/3 of the nuts (vs. cupules almost completely covering the nut in Lithocarpus macphailii and Lithocarpus encleisocarpus ), surface of the cupule densely tomentose inside and subtle hairy to very subtle hairy outside (vs. outside densely fulvous tomentose in Lithocarpus macphailii and outside densely fulvous tomentose by stellate hairs in Lithocarpus encleisocarpus ), leaf blades glabrous adaxially, undersides covered with very short soft hairs and subtle (vs. densely glaucous tomentose with adpressed, stellate hairs abaxially in Lithocarpus macphailii , pubescent then glabrescent abaxially in Lithocarpus encleisocarpus ), secondary veins 11-12 pairs (vs. 12-16 pairs in Lithocarpus macphailii and 8-10 pairs in Lithocarpus encleisocarpus ).

Type.

VIETNAM. Lam Dong Province, Da Huoai, along the 20 National Highway , in the lowland evergreen forest, alt. 225 m, 11°23'32.5"N, 107°33'56.3"E, 14 June 2015, N. Nguyen, D. Luong, B. Hoang, T. Nguyen V3194 (holotype: KYO!; isotypes: DLU!, FU!, HN!, K!, P!, VNM!) .

Description.

Evergreen tree, up to 35 m tall; young branchlets pubescent with white hairs, soon glabrous, greyish green in vivo and blackish brown in sicco; terminal buds ca. 10-12 mm long, bud scale 4-6 mm long, densely covered with whitish hairs. Stipules not seen. Leaves alternate, blades broadly elliptic to slightly obovate, ca. 15-27 × 6-11 cm, thickly coriaceous, base cuneate, margin entire, slightly recurved, apex acuminate or caudate, acumen ca. 5-10 mm long, glabrous adaxially, subtle short soft hairs abaxially; midrib slightly raised above, distinctly raised below glabrous, greenish yellow in vivo, reddish brown in sicco; secondary veins 11-12 pairs, clearly visible on both sides, flat to slightly prominent adaxially, prominent abaxially, veins curving smoothly and disappearing near margins, at an angle of 55-65 degree from the midrib, tertiary veins scalariform, invisible to faintly visible on both surfaces; petioles ca. 10-15 mm long, rounded, thickened, pubescent when young, glabrescent later. Flowers not seen. Infructescences erect, woody, 25 cm long, rachis densely adpressed hairy. Acorn solitary, ovoid or turbinate, 13-15 mm in height, 20-23 mm in diam. (including cupule); fruiting stalk 3-5 mm long, densely fulvous tomentose hair. Cupules, turbinate, base a little broader than the upper part, densely tomentose inside and invisible or subtle hairy outside, lamellate, wall woody, sometimes crackled, enclosing ca. 1/2-2/3 of the nut, 12-14 mm in height, 19-22 mm in diam., bractlets triangular, obscure, forming 6-7 dimly concentric flanges. Mature nut 19-22 mm in height, 20-23 mm in diam., densely white tomentose; scar created by cupule at the base is deeply concave, ca. 13-15 mm in diam.; wall woody, crackled; apex abruptly acuminate, ca. 1.5-2 mm in height.

Phenology.

Mature fruits were collected in June.

Distribution and habitat.

Vietnam (so far known from Lam Dong Province and Dong Nai Province split by a boundary along National highway 20). (Figure 1 )

Etymology.

The specific epithet is derived from the type locality, Da Huoai, Lam Dong Province, Central Highland Vietnam.

Conservation status.

Data Deficient (DD). Three fruiting individuals were found at the type locality, along the Chuoi pass of the 20 National highway. In addition, a staff member of Dong Nai Culture and Nature Reserve has collected this species at Ma Da, Vinh Cuu, Dong Nai Province, indicating its wide distribution around the type locality. However, at present we have no reliable information on its population size. Further investigations are needed to determine the conservation status and actual population size in its natural habitat.

Figures

Figure 1. Distribution map of Lithocarpus dahuoaiensis Ngoc & L. V. Dung. Black triangle, Da Huoai, Lam Dong Province (Type locality); White triangle, Dong Nai Culture and Nature Reserve, Dong Nai Province.

Figure 2. Lithocarpus dahuoaiensis Ngoc & L. V. Dung. A Leafy twig B Buds C Petiole D Abaxial surface of mature Leaf E Infructescence F Mature fruit G Cupule (left) and bottom of nut (right) H Vertical sections of nut.

Figure 3. Line drawing of Lithocarpus dahuoaiensis Ngoc & L. V. Dung. A Leafy twig B Infructescence C, D Cupule E Vertical section of mature nut F, G Mature nut. Scale bars A, B = 5 cm; C - G = 10 mm.