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Luu, Hong Truong, Duong, Quoc Hung, Le, Khac Quyet, Lin, Che-Wei (2022): Begonia yentuensis and B. khaucaensis (Begoniaceae), two new species from northern Vietnam. Phytotaxa 560 (2): 222-232, DOI: 10.11646/phytotaxa.560.2.5, URL: http://dx.doi.org/10.11646/phytotaxa.560.2.5

Begonia yentuensis Luu & C.W. Lin, sp. nov. (Figs. 1 & 2) Type: — VIETNAM. Bac Giang Province: Yen Tu Mountain Range, Tay Yen Tu Nature Reserve, N21°09’58” E106°46’34”, 498 m elev., 09 August 2013, Luu Hong Truong, Hoang Minh Duc, Le Khac Quyet & Duong Quoc Hung TYT22 (holotype: SGN; isotypes: SGN, PHH & TAIF). Monoecious tuberous herb. Stem tuberous at base, tubers globose up to ca. 3 cm with numerous fibrous roots, stemless or sometimes producing leafless erect stem to 3 cm long, ca. 5 mm across, crimson, glabrous. Stipules yellowish pink to red, very widely triangular, 2–3 mm long, 4–6 mm wide, herbaceous, abaxially strongly aristate-keeled near tip of the midrib up to 8 mm long, margin ciliate; stipules at erect stem red, triangular, ca. 3–4 × 3 mm, herbaceous, slightly keeled, glabrous, margin entire to ciliate, apex acute and mucronate. Leaves solitary, nearly appressed to substrate; petiole terete, yellowish pink, 1–7 cm long, 3–6 mm across, adaxially densely hirsute, subglabrous abaxially; leaf blades symmetric or subsymmetric, very widely ovate to orbicular, undivided or with irregular pointed shallowly lobes ca. 3–10 mm long, blade 9–23 cm long, 8.2–24 cm wide, basal lobes cordate, 1.5–5 cm long, apex acute, margin biserrate and ciliate; leaf thick chartaceous, succulent, adaxially olive green to dusky green, slightly bullate and puberulous between veins, giving lamina a wrinkled texture; abaxially magenta to brownish red, puberulous and hirsute on veins; venation palmate, midrib distinguishable, 6–18 cm long, ca. 2 major lateral veins on either side of midrib, other primary veins branching dichotomously, tertiary veins reticulate. Inflorescences terminal on erect stem or arising directly from tuber, bisexual, cymosely branching panicle 7–25 cm long, peduncle 4–12.5 cm long, branched 3–5 times, erect, red, glabrous; protandrous. Bracts deciduous, red, ovate-triangular to ovate, first pair 7–10 × 5–7 mm, glabrous, margin ciliate, bracts of upper inflorescence similar but smaller. Staminate flower: pedicel creamy pink to red, 1.3–2 cm long, glabrous, tepals 4, white to pink, glabrous; outer 2, orbicular to widely ovate, 11−13 mm across; inner 2, obovate, 9–12 mm long, 5–6.5 mm wide, apex rounded; androecium zygomorphic, ca. 3.5 mm across; stamens yellow, 17–25; filaments shortly fused at base; anthers oblong, ca. 1 mm long, 2-locular, apex rounded, filaments ca. 1 mm long. Pistillate flower: pedicel red, 0.7–2.5 cm long, glabrous, ovary pale creamy green, trigonous-ellipsoid, 8–10 mm long, ca. 5 mm thick (wings excluded), glabrous; 3-winged, wings unequal, triangular, 11–13 mm long, glabrous; lateral wings narrower, 2–4 mm wide, abaxial wing 5–7 mm wide, margin entire; ovary 3-locular, placenta undivided; tepals 5 (rarely 4), white to pink, glabrous, outer 2, orbicular, 8–12 mm across; inner 3, suborbicular to obovate, 6–11 mm long, 5–10 mm wide, apex rounded; styles 3, fused at base, yellow, 2–3 mm long, stigma spirally twisted. Capsule capsule body ca. 15 mm long, 7.5 mm across, glabrous; wings 3, unequal, 16–18 mm long, lateral wings to 5 mm wide, abaxial wing to 13 mm wide, rounded to truncate proximally, truncate distally, splitting between the locules and wings. Distribution and ecology:— Begonia yentuensis is endemic to Bac Giang Province, North Vietnam. It is a deciduous lithophyte growing on sandstone rock under the canopy of a secondary moist tropical evergreen forest dominated by species of the Magnoliaceae, Fagaceae and Lauraceae mixed with bamboos. Phenology:— Flowering was found in July to September and fruiting starting in August. Etymology:— The species is named after its type locality, Yen Tu Mountain Range. Conservation status:— Begonia yentuensis was found in western slopes of the Yen Tu Mountain Range and appears to be rare within Tay Yen Tu Nature Reserve and fewer than 100 mature individuals. It may be found in adjacent forests of the Yen Tu Mountain Range. Therefore, we provisionally propose its conservation status as Data Deficient until more information is recorded (IUCN Standards and Petitions Subcommittee, 2022). Notes:— Begonia yentuensis resembles B. asperifolia Irmsch. (1927: 359) (Fig. 3) in its winter dormant habit, subsymmetric, rugose foliage, 4-tepaled staminate flowers and pistillate flowers with 5 tepals, but it is different in its shorter petioles up to 7 (vs. to 28) cm long, androecium golfclub-shaped (vs. spherical), filaments fused at base (vs. fused at base into a column ca. 2 mm long), anthers less than 25 (vs. more than 50), apex rounded (vs. acute to mucronate) and placentae unilamellate (vs. bilamellate). Like B. asperifolia, according to phenotypic morphology and geographical origin, B. yentuensis is best placed within the group known as “unassigned to section with tubers” that belongs to Begonia subg. Platycentrum in Shui’s system. Molecular studies are necessary to confirm if there are trait combinations or new morphological traits suitable for creating a new section, or assigning the species to a known section. In the subsymmetric, solitary leaf and terminal inflorescence, B. yentuensis is also similar to B. labordei H. Léveillé (1904: 323) (Fig. 4), but differs in the rugose (vs. flat) foliage, cymose inflorescence (vs. racemose at base), pistillate tepals 4 or 5 (vs. 3 or 4) and actinomorphic (vs. zygomorphic), ovary glabrous (vs. often hairy) and placentae unilamellate (vs. bilamellate). A comparison of the salient characters of the three species is presented in Table 1.

Begonia khaucaensis Luu & C.W.Lin, sp. nov. (Figs. 5 & 6) Type:— VIETNAM. Ha Giang Province: Dong Van Karst Plateau - Du Gia National Park, Khau Ca Forest, 22°50’54”N 105°7’16”E, 800m elev., 22 October 2016, Luu Hong Truong & Le Khac Quyet HG 6 (holotype: SGN; isotypes: SGN, PHH & TAIF). Monoecious rhizomatous herb. Rhizome stout, creeping, crimson, ca. 1 cm thick, internodes 0.5–3 cm long, hirsute. Stipules crimson to reddish olive green, widely triangular, 1.5–2.5 cm long, 1.2–2.3 cm wide, herbaceous, keeled, abaxial midrib scattered with white hirsute, margin entire, apex aristate, arista ca. 3 mm long. Leaves alternate, petiole terete, crimson to dark brownish red, 18–30 cm long, 0.5–1 cm thick, lenticels slightly prominent, creamy white, sparsely to densely hirsute, glabrescent; leaf blade asymmetric, suborbicular to reniform, oblique, with a welldeveloped basal lobe on one side giving a cordate appearance, 17.5−27 cm long, 15–23 cm wide, broad side 9.5–16 cm wide, basal lobes cordate, 5–11 cm long, margin sparsely denticulate to subentire, apex acuminate; leaf thin coriaceous, succulent, adaxially emerald green (vermilion to greenish maroon when juvenile), sparsely bullate between veins, bulla tipped white hirsute, glabrescent; abaxially pale green, veins pale red; venation basally 7–9 palmate, midrib distinct, ca. 2 secondary veins on each side, lateral through connection between with other basal veins, minor veins reticulate. Inflorescences axillary, dichasial cymes, arising directly from rhizome, branched up to 5 times; bisexual, cymosely branching panicle 16–30 cm long, peduncle olive green to crimson, 13–25 cm long, glabrous. Bracts white to rosy red, orbicular to very widely ovate, first pair up to 2.5 cm across, glabrous, margin entire, apex retuse to rounded or apiculate; bracts of upper inflorescence similar but smaller. Staminate flower: pedicel white to pink, 0.8–2 cm long, glabrous; tepals 4, white to rosy pink, glabrous; outer 2, very widely obovate to orbicular, 12–15 mm long, 13–16 mm wide; inner 2, elliptic, ca. 7 mm long, 3 mm wide; androecium zygomorphic, ca. 5 mm across; stamens golden yellow, 40–65, filaments fused at base, anthers narrowly obovate-triangular, ca. 1.5 mm long, 2-locular, apex truncate to slightly retuse, shorter than filaments. Pistillate flower: pedicel pinkish white to rosy pink, 1.7–2 cm long, glabrous; tepals 3, rosy pink to white, glabrous; outer 2, orbicular to widely depressed ovate, 9–14 mm long, 8–15 mm wide; inner 1, elliptic, 5–8 mm long, 2–3 mm wide; ovary narrowly trigonous-ellipsoid, 6–8 mm long, ca. 3 mm thick (wings excluded), pink to white, 3-winged; wings unequal, pinkish white, 8–10 mm long, lateral wings narrower, narrowly crescent-shaped, 1.5–2.5 mm wide, abaxial wing crescent-shaped, ca. 4 mm wide, margin entire; ovary 3-locular, placenta bilamellate; styles 3, fused at base, golden yellow, ca. 3.5 mm long, stigma spirally twisted. Capsule pendent on a stalk 28–37 mm long, tepals persistent, capsule ca. 15 mm long, 1 cm thick (wings included), wings unequal, crescent-shaped, rounded to cuneate proximally, rounded distally. Distribution and ecology:— Endemic to Du Gia National Park in Ha Giang Province. The new species is an evergreen lithophyte growing on damp limestone rock under the canopy of tropical evergreen forests dominated by Burretiodendron hsienmu W.Y.Chun & F.C.How (Malvaceae) and species of the Clusiaceae, Sapindaceae, Ebenaceae, Euphorbiaceae, Aceraceae, Araliaceae and Fagaceae. Phenology:— Flowering was seen in October and November, and fruiting starting in November. Etymology:— The species is named after its type locality, Khau Ca Forest. Conservation status:— Least Concern (LC) (IUCN Standards and Petitions Subcommittee, 2022). Begonia khaucaensis appears to be abundant and well protected within the Khau Ca Forest of Dong Van Karst Plateau - Du Gia National Park. No threats to its existence were seen. Notes:— B. khaucaensis is restricted to limestone regions, and it has characters such as rhizomatous habit, axillary inflorescence and 3-tepaled pistillate flowers. These characters are shared by sect. Coelocentrum, however, it is also similar with the broad delimitation of sect. Petermannia in Shui’s system (2019) in many aspects. We are unable to appropriately allocate this new species to any section until molecular information is available. Begonia khaucaensis somewhat resembles B. jubar V.T.Pham & C.W. Lin (2021: 145) in its rhizomatous habit, 4-tepaled staminate flowers and 3-tepaled pistillate flowers with 3-locular ovaries with blamellate placentae, but it is different from B. jubar in its hairy stipules (vs. glabrous), sparsely to densely hirsute petioles (vs. glabrous), suborbicular to reniform leaves (vs. ovate to widely ovate with slightly polygonal outline), entire bract margins (vs. denticulate to serrate with very short soft hairs), zygomorphic androecium (vs. actinomorphic or nearly so) and crescent-shaped ovary wings (vs. triangular). Moreover, B. khaucaensis bears some resemblance to B. quadripetiolata Aver. & H.Q.Nguyen (2019: 135) in the rhizomatous habit, uniformly green leaves, 4-tepaled staminate flowers and the bilamellate placentae, however, the new species markedly differs in the petioles have a terete outline (vs. quadrate), leaf upperside very sparsely hirsute hairs (vs. glabrous), zygomorphic (vs. actinomorphic) androecium and 3-tepaled (vs. 5-tepaled) pistillate flowers. A detailed comparison of B. khaucaensis with these two phenetically similar species are presented in Table 2., Published as part of Luu, Hong Truong, Duong, Quoc Hung, Le, Khac Quyet & Lin, Che-Wei, 2022, Begonia yentuensis and B. khaucaensis (Begoniaceae), two new species from northern Vietnam, pp. 222-232 in Phytotaxa 560 (2) on pages 227-230, DOI: 10.11646/phytotaxa.560.2.5, http://zenodo.org/record/7040690, {"references":["Lin, C. W., Phan, L. C. S. & Nguyen, N. H. (2021) Begonia rigidifolia ssp. sonhungii (sect. Petermannia, Begoniaceae), a new subspecies from limestone hills in Central Vietnam. Phytotaxa 498 (2): 139 - 144. https: // doi. org / 10.11646 / phytotaxa. 498.2.7"]}