Begonia minhaniae T.S.Hoang & C.W.Lin, 2022

HOANG, THANH SON & LIN, CHE-WEI, 2022, Two new species, Begonia minhaniae and B. dieuanhiae (sect. Platycentrum, Begoniaceae), from northwestern Vietnam, Phytotaxa 572 (1), pp. 87-96 : 87-88

Begonia minhaniae T.S.Hoang & C.W.Lin , sp. nov. § Platycentrum ( Figs. 2 & 3 )

Type:— VIETNAM: Yen Bai province, Van Tran District , 21.707777N, 104.341748E, 512 m elevation, 22 July 2021, flowers and fruits, Hoang Thanh Son 8754 (Holotype VAFS; Isotypes VNMN) .

Monoecious rhizomatous herb. Rhizome stout, reddish-brown, 3–5 cm or longer, 5−7 mm thick, internodes 2−7 mm long, sparsely pale brown tomentose. Stipules often caducous, yellow tinged crimson, triangular to very widely ovate-triangular, 4–6 × 3–7 mm, herbaceous, keeled, glabrous or abaxially sparsely tomentose, margin ciliate, apex obtuse to rounded and mucronate. Leaves alternate, petiole terete, brownish-red to crimson, 4−10 cm long, 2−4.5 mm diameter, densely subappressed yellowish-brown tomentose; leaf blade asymmetric, oblique, widely ovate, 8.5−12.5 × 6–9.5 cm, broad side 3.6–5.5 cm wide, basal lobes cordate, 1.6–3 cm long, apex acute to acuminate, margin subentire to crenulate with a line of red puberulous hairs; leaf chartaceous, succulent, adaxially lime green, glabrous; abaxially pale green, glabrous except on veins; venation basally ca. 7 palmate, veins green adaxially, yellowish-green and sparsely red puberulous abaxially; midrib distinct, ca. 2 secondary veins on each side, other primary veins branching dichotomously or nearly so, tertiary veins reticulate. Inflorescences axillary, bisexual, cymose arising directly from rhizome, ca. 2 orders of branching; peduncle reddish-green to crimson, ca. 10 cm long, sparsely yellowish-brown tomentose. Bracts caducous, yellowish-red to pale brown, at basal node of inflorescence ovate, ca. 4 × 2 mm, abaxially sparsely yellowish-brown tomentose or glabrous, margin ciliate; bracts of upper inflorescence similar but smaller. Staminate flower: pedicel yellowish-red, ca. 2 cm long, very sparsely yellowish-brown tomentose, tepals 4, pink, outer 2 orbicular to very widely ovate, ca. 1 cm across, adaxially very sparsely puberulous or glabrous, margin entire, apex rounded, inner 2 elliptic, ca. 10 × 6 mm, glabrous, apex rounded; androecium zygomorphic, ca. 3.5 mm across; stamens golden yellow, ca. 15; filaments ca. 2 mm long, fused at base; anthers obovate, ca. 1.5 mm long, 2-locular, apex slightly retuse. Pistillate flower (immature): pedicel ca. 5 mm long with a pairs alternate bracteoles ca. 2 × 1 mm, ciliate; sparsely yellowish-brown tomentose, tepals 3, pink, outer 2 orbicular, ca. 8 mm across, subglabrous; inner 1 obovate, ca. 7 × 2.5 mm; ovary trigonous-ellipsoid, ca. 5 × 2.5 mm; 3-winged, wings unequal, ca. 6 mm long, lateral wings narrower, narrowly triangular, abaxial wing triangular, margin entire, glabrous or sparsely tomentose; ovary 3-locular, placenta bilamellate; styles 3, fused at base, yellow, U-shaped, stigma spirally twisted. Capsule trigonousellipsoid, ca. 9 mm long, 6 mm thick (wings excluded), reddish-green when fresh; wings unequal, ca. 11 mm long, lateral wings ca. 2 mm wide, abaxial wing triangular, ca. 5 mm wide.

Distribution and ecology:— Begonia minhaniae is only known from the type locality in Van Tran District. It grows on moist cliff faces in shady lower primary evergreen broad-leaved forests, elevation ca. 512 m.

Etymology:— The species is named in honor of Ms. Minh An Hoang, the second daughter of the first author. She is always the first author’s motivation to research and find new species.

Conservation status:— We assess B. minhaniae to be Endangered based on criteria ENC2a(i) (IUCN 2022). This species has only four known populations in one single location with the number of mature individuals being less than 100, all of the populations were in areas which have no formal legal protection (its distribution overlapping the Mu Cang Chai Protection Forest, but it is not included on any national protected areas system). In the areas, the most prominent threat to the new species is deforestation, along with other human activities such as such as farming from around the habitat, which means it is prone to the risk of extinction due to chance events.

Notes:— Like Begonia phouchomvoyensis Lanors., Lamxay & Souvann. (Lanorsavanh et al., 2020), this new species belongs to sect. Platycentrum. The two share several characters including rhizomatous habit, hairy petioles and abaxial lamina, 4-tepaled staminate flowers, pistillate flowers with 3 tepals and ovary 3 locules, but the new species can be distinguished by its stipule margin ciliate (vs. entire), the petiole densely subappressed yellowish-brown tomentose (vs. red villous), the leaf is glabrous on the adaxial surface (vs. strigose), the peduncle sparsely yellowish-brown tomentose (vs. red villous) and pedicel of pistillate flowers with two bracteoles (vs. bracteoles absent). A comparison of B. minhaniae and B. phouchomvoyensis is presented in Table 1 . The character of pistillate flowers with unequal 3 tepals is uncommon in sect. Platycentrum, shared between B. phouchomvoyensis and B. minhaniae .

Figures

FIGURE 2. Begonia minhaniae T.S.Hoang & C.W.Lin. A. Habit; B, B’. Portion of leaf, upper and lower surfaces; C. Stipule; D, D’. Bracts; E, E’. Staminate flower, face and side views; F, F’, F’’. Stamens, dorsal, ventral and side views; G, G’. Immature pistillate flower, face and side views; H, H’. Style and stigmatic band, dorsal and ventral views; I. Cross section of ovary.

FIGURE 3. Begonia minhaniae T.S.Hoang & C.W.Lin. A, B. Habit and habitat; C. Young leaf, also showing stipules, petiole and peduncle; D, E. Portion of leaf, upper and lower surfaces; F. Habit; G. Inflorescence; H. Immature staminate and pistillate flowers, also showing bracts and bracteoles; I. Immature staminate flowers; J. Cross section of an old capsule.