Begonia laotica Y.H.Tan & H.B.Ding, 2020

Ding, Hong-Bo, Maw, Mya Bhone, Yang, Bin, Bouamanivong, Somsanith & Tan, Yun-Hong, 2020, An updated checklist of Begonia (Begoniaceae) in Laos, with two new species and five new records, PhytoKeys 138, pp. 187-201 : 187

Begonia laotica Y.H.Tan & H.B.Ding sp. nov. Figure 1

sect. Parvibegonia A. de Candolle

Diagnosis.

The new species is mostly similar to B. josephii A. de Candolle (1859: 126) in its peltate, stemless, tuberous habit, but significantly differs by fleshy reddish bristles at the petiole apex (vs. without), ovary 2-locular (vs. 3-locular) and styles 2 (vs. 3).

Type.

Laos. Oudomxay Province, Maung Xai, Phou Hin Phee National Biodiversity Conservation Area, 20°43'18.69"N, 102°08'47.97"E. 1378 m elev., 25 October 2018, flowering, Y.H. Tan & H.B. Ding L0827 (holotype: HITBC!; isotypes: HNL!).

Description.

Monoecious herb, stemless, tuberous, 18-25 cm high, tuber small, subglobose, 12-15 mm in diameter. Stipule: broadly lanceolate, 2-3 mm long, membranous, sparsely glandular hairy, margin fringed by hairs, deciduous. Leaf: petiole 6-15 cm long, glabrous or sparsely puberulous; blade ovate, nearly symmetric, 9.2-13.5 × 5.8-11 cm, peltate, base rounded, apex acuminate, margin slightly denticulate, with sparse short hairs, upper surface green, glabrous, lower surface paler, venation palmate-pinnate, tomentose on the veins, fleshy reddish bristles at the petiole apex, thinly succulent in life, thinly papery when dried. Inflorescence: axillary, terminal cyme; peduncle puberulent, 7.2-10.9 cm long, branching 2-3 times; bracts narrowly ovate, ca. 4.0 × 2.5 mm, membranous, reddish line along the middle, slightly glandular hairy, margin fringed by glandular hairs. Staminate flower: pedicel 1.1-1.8 cm, membranous, covered with glandular hairs, tepals 4, pink, unequal, outer 2, ovate, 10-13 × 7-17 mm, glandular hairs on the outer surface, margin entire, inner 2, elliptic, 7-10 × 2-4 mm, glabrous, margin entire; stamens 15-20, anther obovate, ca. 1 mm. Pistillate flower (young): pedicel 0.9-1.2 cm long, membranous, glandular hairy, tepals 5, pink, unequal, outer 2, ovate, 4-6 × 3-4 mm, inner 2, elliptic, 3-5 × 1-3 mm, glandular hairs on the outer surface, especially at the base; ovary 2-locular, placentae axial, placentae 2 per locule, styles 2, stigmas bifid with twisted bands, highly convolute, golden yellow. Capsule nodding, obovate, pinkish tomentose, unequally 3-winged, abaxial wing oblong, ca. 13 mm long, lateral wings shorter, ca. 3 mm long.

Phenology.

Flowering in October-November and fruiting in December.

Distribution.

Endemic to the type locality, Oudomxay Province, Maung Xai, Phou Hin Phee National Biodiversity Conservation Area, Laos.

Ecology.

Restricted to the shaded base of limestone cliff at ca. 1378 m elevation.

Etymology.

The specific epithet ' laotica ' refers to the type locality in Laos.

Conservation status.

Data Deficient (DD) ( IUCN 2017). The new species was only collected from the limestone cliff of Hin Phee National Biodiversity Conservation Area. Due to its remote habitat, we suggested that the species may not suffer from strong human disturbance. According to the available information, we proposed the preliminary conservation status of this new species as Data Deficient (DD) ( IUCN 2017).

Notes.

Begonia laotica is phenotypically most similar to B. josephii in its tuberous habit, ovate and peltate leaves, but it can easily be distinguished by its glabrous upper leaf surface (vs. hispid all over), fleshy reddish bristles at the petiole apex (vs. without), bracts narrowly ovate and fringed by glandular hairs (vs. lanceolate and glabrous), male flowers pedicels with glandular hair (vs. glabrous), outer tepals ovate (vs. broadly obovate), inner tepals elliptic (vs. spathulate), anther obovate (vs. ellipsoid), female flowers pedicels with sparsely glandular hair (vs. glabrous), glandular hair on the outer surface (vs. glabrous), ovary 2-locular (vs. 3-locular) and styles 2 (vs. 3). This new species also shares similar characteristics with B. subperfoliata Parish ex Kurz (1873: 81) in tuberous habit and peltate leaves, but it can easily be distinguished by its ovary 2-locular (vs. 3-locular) and styles 2 (vs. 3).

Figures

Figure 1. Begonia laotica Y. H. Tan & H. B. Ding, sp. nov. A habitat B leaf blade adaxially C leaf blade abaxially (showing fleshy reddish bristles at the petiole apex) D flowers (front view) E flowers (lateral view) F inflorescence G mature fruits H habit I staminate flower J pistillate flower (young) K stamens (lateral view) L stamens (front view) M cross section of ovary. Photographed by H. B. Ding.