Quercus mangdenensis H.T.Binh & Ngoc, 2022

Ngoc, Nguyen Van & Binh, Hoang Thi, 2022, Quercus mangdenensis, a new species of Quercus (Fagaceae) from Kon Tum Province, Vietnam, PhytoKeys 215, pp. 73-79 : 73

Quercus mangdenensis H.T.Binh & Ngoc sp. nov.

Fig. 2

Diagnosis.

Quercus mangdenensis is morphologically most similar to Q. bidoupensis and Q. kontumensis with a lanceolate to oblong-lanceolate leaf shape, cuneate leaf base, and bracts of cupule fusing in 5-7 rings. However, Q. mangdenensis is distinguished from Q. bidoupensis by its entire leaf margin (vs. undulate, distinctly serrate in the upper 1/2), longer petioles 2.5-4 cm long (vs. 1.3-2 cm long), broadly bowl-shaped cupules (vs. obconical-shaped), larger cupule (2.6-3.5 cm high × 4-5 cm in diam. vs. 1.3-1.5 cm high × 1.3-1.7 cm in diam.), enclosure of cupule (1/5 vs. 1/3 of the nut), cylindrical-ellipsoid nut (vs. ovoid), larger nut (4.5-7.5 cm high × 3-4 cm in diam. vs. 2.2 cm high × 1.4 cm in diam.), and flat basal scar of the nut (vs. convex). It differs from Q. kontumensis in having larger cupule enclosing 1/5 of the nut (2.6-3.5 cm high × 4-5 cm in diam. vs. 1-1.2 cm long × 1.5-2 cm in diam., enclosing 1/2 of the nut), larger cylindrical-ellipsoid nut 4.5-7.5 cm high × 3-4 cm in diam. (vs. cylindrical-ovoid, 2 cm high × 1.5 cm in diam.), and scales of cupule fusing into 5-7 entire ridges (vs. undulate) (Table 1 ).

Type.

Vietnam. Kontum Province, Kon Plong District, Mang Den Town , alt. 1179 m, 14°36'39.1"N, 108°15'00.5"E, 23 July 2022, H.T. Binh & N.V. Ngoc QC204 (holotype DLU!; isotypes HN!, VNM!)

Description.

Tree, evergreen, 20-25 m tall, 60-80 cm girth. Bark whitish gray. Buds perulate, globose to oblate, 2.5-4 mm high, 2.5-3.5 mm in diam., bud scales imbricate, in 2-3 rows, ovate-triangular, 2.0-3.0 × 1.5-2.0 mm, apex obtuse, margin ciliate, covered with appressed white hairy outside, glabrous inside. Young twigs dark pale green, hairy, old twigs grayish-brown, glabrous, sometimes sulcate, lenticellate. Leave alternate; blades thickly coriaceous, lanceolate to oblong-lanceolate, (5.5-)11-16.5(-19.5) × (2.6-)3.5-5.5 cm, acute at apex, broadly cuneate at base, margin entire, glossy green adaxially, bright green abaxially, conspicuously pale creamy brown to yellowish brown in sicco, glabrous on both surfaces, midrib slightly raised on the upper surface, prominently raised on the lower surface, lateral veins (5-)7-9 pairs, prominent on the lower surface, at an angle of 45-55 degree from the midrib, straight and then curved near margin, tertiary veins scalariform-reticulate, faintly visible on both surfaces; petioles (1.3-)2.5-4 cm long, yellowish brown when dry, glabrous. Male and female inflorescences not seen. Infructescences axillary or pseudo-terminal (sometimes in upper leaf-scars), erect, rachis 1-1.5 cm long, 1-1.3 cm in diam., woody, glabrous, dark yellow in vivo, yellowish brown in sicco, lenticellate. Mature fruits 6-10.5 cm high (including cupule), solitary, sessile on woody rachis; nuts cylindrical-ellipsoid, 4.5-7.5 cm high, 3-4 cm in diam., rounded at the top, white tomentose around stylopodia, stylopodia 1.5-2.5 mm long, basal scar 2-2.5 cm in diam., flat; cupules broadly bowl-shaped, 2.6-3.5 cm high, 4-5 cm in diam., enclosing 1/5 of the nut when mature, outside tomentose with reddish hairs to glabrous, inside with appressed densely reddish hairs, wall 0.5-1.3 cm thick, woody, bracts fusing and arranged in 5-7 ridges (rings), the rings’ margin completely entire (without scale-like structure).

Distribution.

Vietnam. Kon Tum Province, Kon Plong District, Mang Den Town (Fig. 1 ).

Habitat.

Quercus mangdenensis were found in the scattered evergreen forest, from 1050 to 1200 m elevation.

Etymology.

The specific epithet is derived from its type locality, Mang Den Town, Kon Plong District, Kon Tum Province, Vietnam.

Vernacular name.

Sồi Măng Đen (suggested here).

Phenology.

Fruiting specimens and fallen mature fruits were collected in July.

Additional specimens examined.

Vietnam. Kontum Province, Kon Plong District, Mang Den , alt. 1168 m, 14°36'37.4"N, 108°15'11.6"E, 23 July 2022, H.T. Binh & N.V. Ngoc QC205 [fr.] (DLU!, HN!, VNM!) ; ibid., 1180 m elev., 14°36'32.5"N, 108°15'18.2"E, 23 July 2022, H.T. Binh & N.V. Ngoc QC207 [fr.] (DLU!, HN!, VNM) ; ibid., 1130 m elev., 14°36'36.5"N, 108°15'31.3"E, 23 July 2022, H.T. Binh & N.V. Ngoc QC208 [fr.] (DLU!, HN!, VNM) ; ibid., 1065 m elev., 14°36'36.5"N, 108°15'31.3"E, 23 July 2022, H.T. Binh & N.V. Ngoc QC209 [fr.] (DLU!, HN!, VNM!) .

Preliminary conservation status.

Our botanical inventories were conducted at Mang Den and the surrounding areas from April to July 2022 and we found five subpopulations of 5-7 mature individuals of Quercus mangdenensis in the scattered evergreen forests. In addition, the forest in this area is severely fragmented and continuing to decline caused by human activities, such as farming, logging, and harvesting of non-timber forest products, etc., while almost all of the individuals of Q. mangdenensis are distributed along the boundary between the evergreen forest and local people’s farms. According to criterion D of the IUCN Red List criteria ( IUCN 2019), the species classifies as Critically Endangered (CR). The area of occupancy (AOO) and the extent of occurrence (EOO) were calculated are 0.415 km2 and 8.0 km2, respectively. Based on criterion B of the IUCN Red List criteria ( IUCN 2019), the new species is qualified as Critically Endangered [CR B1ab(i,ii,iii,iv,v) B2ab(i,ii,iii,iv,v)].

Figures

Figure 1. Type locality of Quercus mangdenensis Binh & Ngoc A map of Vietnam B map of Kon Tum province C map of Kon Plong District, the red star indicated the type locality: Mang Den Town, Dak Long Commune.

Figure 2. Quercus mangdenensis Binh & Ngoc: A twigs with young fruit B terminal buds C infructescences D fallen mature fruit E, F adaxial and abaxial surface of the leaves G nuts H outside of cupule I densely reddish hairs inside of cupules J basal scar of the nut K, L inside and outside of bud scale. Materials from H. T. Binh and N. V. Ngoc QC 204.