Begonia pendens H.Q.Nguyen,Y.M.Shui & W.H.Chen, 2020

Chen, Wen-Hong, Nguyen, Hieu-Quang, Radbouchoom, Sirilak, Xi, Hui-Hui, Nguyen, Hiep- Tien & Shui, Yu-Min, 2020, Two new baccate species of Begonia sect. Platycentrum (Begoniaceae) from Vietnam, Phytotaxa 443 (1), pp. 92-100 : 94-96

Begonia pendens H.Q.Nguyen,Y.M.Shui & W.H.Chen , sp. nov. ( Fig. 2 )

The new species is similar to Begonia hahiepiana H.Q.Nguyen & Tebbitt in its habit, leaf morphology and 3-loculed ovary, but differs principally in its cylindrical petiole (vs grooved), pistillate flower with obovate outer petals and lanceolate inner petals (vs with broadly oblong outer and inner petals), and fruit trigonous-ellipsoid (vs trigonous-spherical) and ratio of length to width 2.9‒3.4 (vs 1.1‒1.2).

Type:— VIETNAM. Hoa Binh province, Lac Son district, Ngoc Son-Ngo Luong Nature Reserve, Tu Do commune, Coi Gao village , 20°26’55″ N, 105°16’24″E, elev. 560 m, herb, flower white or pinkish, 4 December, 2017, Q. H. Nguyen, Y. M. Shui, W. H. Chen, S. W. Guo, T. H. Nguyen, S. K. Nguyen CK 1728 (Holotype, KUN!, barcode 0756799; isotype, CPC! [=herbarium of Center for Plant Conservation of Vietnam , Hanoi]) .

Herb, rhizomatous, without erect stem. Rhizomes slender, 4‒6.5 cm long, 1‒1.5 cm thick. Stipules persistent, ferrugineous-red, triangular, 1.2‒1.5 × 0.7‒1.2 cm, adaxially glabrous, abaxially densely ferrugineous-red pubescent. Petioles cylindrical, 15.5‒24 cm long, 5‒7 mm diam., densely ferrugineous-red pubescent. Leaves alternate; leaf blade asymmetric, broadly ovate, 13‒19 × 9‒12 cm, apex acute or mucronate, margin with short-ciliate hairs, base cordate; adaxial surface slightly rugose, dark green, sparsely and shortly setose, abaxial surface densely red lanate and strigose along veins; venation palmate, primary veins 6, secondary veins branching dichotomously, tertiary veins reticulate. Inflorescence a dichasial cyme, bisexual, peduncle 10‒12 cm long, 3‒4 mm thick, reddish pubescent, rising from rhizome. Bracts and bracteoles deciduous. Staminate flower: pedicel 35‒50 mm long; tepals 4, white or slightly pinkish-white; outer tepals 2, ovate, 17‒20 × 13‒16 mm, margin entire, apex obtuse and bending downward, base cuneate, abaxially slightly reddish pubescent; inner tepals 2, oblanceolate, white, 12‒15 × 3‒4 mm, margin entire, apex acute to obtuse, base cuneate, glabrous on both sides; stamens numerous; filament longer than anther, fused to 1/3; anthers yellow 0.5‒1 mm long, clavate, apex convex, dehiscing via two longitudinal slits. Pistillate flower: pedicel 12‒15 mm long; tepals 5, white, adaxially glabrous, abaxially ferrugineous-red pubescent; outer tepals 3, obovate, 12‒15 × 7‒10 mm, margin entire, base cuneate, apex acute to obtuse; inner tepals 2, lanceolate, 12‒15 × 3‒4 mm, margin entire, base narrowly cuneate, apex acute; ovary green to yellowish-green, trigonous ellipsoid with short ferrugineous-red pubescence; placentae axile, bifid; styles 3, slightly fused at base; stigma bi-lobed and consisting of a spirally twisted band. Fruits baccate, trigonous and ellipsoid, 17‒20 mm long, 5‒7 mm wide, length- to width ratio 2.9‒3.4, green to yellowish-green, wingless; horns 3, rib-like, 1‒3 × 3‒5 mm.

Phenology:—Flowering October‒January, fruiting November‒February.

Habitat and distribution:—The new species is only known in Hoa Binh and Thanh Hoa provinces, northern Vietnam. It grows in primary, evergreen seasonal broad-leaved forests on slopes of schist/shale in Thanh Hoa province, and in logged closed primary evergreen broad-leaved lowland forests on limestone areas and secondary broad-leaved forest on rocky slopes of limestone hills along stream in Hoa Binh province.

Etymology:—The epithet refers to the similarity of hanging fruits to numerous pendants, a loose-hanging piece of jewelry, attached to a necklace or an ear for ornamental purposes.

IUCN category:—This new species grows on slopes nearby rough roads between villages. There are a total of about 37 mature individuals in two populations ( Fig. 1 ). One population is located in Hoa Binh province with 24 mature individuals in an area ca. 0.022 km 2 (1.1 km × 0.02 km). Another population is in Thanh Hoa province with 13 mature individuals in an area ca. 0.016 km 2 (0.8 km × 0.02 km). However, further field surveys are needed. Nevertheless, human activities (e.g. plantation and deforestation) will make stability of these populations uncertain in the future. Thus, we provisionally considered B. pendens as the “Critically Endangered [CR: B 2a, b (ii, iii)]” species according to Guidelines for Using the IUCN Red List Category and Criteria ( IUCN 2017).

Additional examined specimens:— VIETNAM. Hoa Binh province, Lac Son district, Tu Do municipality, Coi Gao village, 20°26’ 32’’N, 105°16’ 55’’E, elev. 220 m, terrestrial and rosulate herb in shady place, common, 25 March 2011, N.Q. Hieu, L. Averyanov, N.T. Hiep, P.K. Loc, P.V. The, N.T. Vinh, T.B. Ngan, N. Tap, D.D. Dao, V.T. Ha CPC 1516 (CPC!). Thanh Hoa province, Ba Thuoc district, Co Lung municipality, Khuyn village, 20°26’39’’N, 105°15’33’’E, terrestrial herb, flowers white, leaves uniform metallic green above, brown-pink below, occasional, 20 September 2003, L. Averyanov, D.T. Doan, J. Regalado, N.T. Vinh HAL 3148 (CPC!). The same locality, 20°26’ 34’’N, 105°15’ 50’’E, elev. 216 m, in fruit, 12 Dec, 2017, Q.H. Nguyen, Y.M. Shui, W.H. Chen, S.W. Guo, T.H. Nguyen, S.K. Nguyen CK 1869 (KUN!, CPC!).

Note: —The new species was firstly discovered by L.Averyanov, D.T. Doan, J. Regalado, N.T. Vinh in 2003 during a FFI Pu Luong - Cuc Phuong Conservation Project. In 2016, one of the authors (H.Q. Nguyen) saw it again at Ngoc Son-Ngo Luong Nature Reserve in Hoa Binh province. During a 2017 joint survey conducted by Kunming Institute of Botany and the Center for Conservation of Vietnam, we collected it both in Hoa Binh and Thanh Hoa provinces, and made detailed observations of the flowers, ovaries and fruits, and finally confirmed it as a new species.

The new species is similar to B. hahiepiana in its broadly ovate leaves and hairy trigonous fruits, but differs mainly in its ellipsoid instead of spherical ovaries and fruits. Furthermore, the reticulate red nerves on the adaxial surface of the leaves implies that the new species is also closely related to B. albopunctata . We compared the new species with B. hahiepiana and B. albopunctata in female flowers and fruits based on the previous publications ( Nguyen & Tebbitt 2006, Chen et al. 2018, Hughes et al. 2018). The detailed differences among the new species and its two similar species have been shown in Table 1 and figures in the related publications ( Shui & Huang 1999, Tebbitt 2003, Nguyen & Tebbitt 2006, Chen et al. 2018, Hughes & Peng 2018).

In Northern Vietnam and South China, the new baccate species and B. hahiepiana seem to be related to B. gulinqingensis Huang & Shui (1994: 334) , a capsular species from China in the broadly ovate leaves and reticulate nerves on the adaxial surface of leaves, but different in having baccate fruits of the two former species instead of capsules in B. gulinqingensis . The three related species seems to form a species complex indicating the evolutionary process from the baccate fruits to the capsular ones ( Fig. 2 F , Wilde 2011, Shui & Chen 2017, Hughes et al. 2018).

Characters B. pendens sp. nov. B. hahiepiana B. albopunctata

Leaf blade broadly ovate or round broadly ovate or round oblong-ovate

Petiole cylindrical grooved cylindrical

Sex system monoecious monoecious dioecious

Pistillate outer tepal obovate broadly oblong broadly ovate

Pistillate inner tepal lanceolate broadly oblong ovate

Ovary surface densely pubescent sparsely pubescent glabrous

Ovary locules 3 3 4

Fruit trigonous-ellipsoid trigonous-spherical tetragonous-spherical

Figures

FIGURE 1. The geographical distribution of Begonia pendens H.Q. Nguyen, Y.M. Shui & W.H. Chen sp. nov. (square) and Begonia satelloides Y.M. Shui, H.Q. Nguyen & W.H. Chen sp. nov. (triangle).

FIGURE 2. Begonia pendens H.Q.Nguyen, Y.M.Shui & W.H.Chen sp. nov. (All from holotype) A. Plant and habitat; B. Rhizome; B’. Stipules; C. Adaxial view of leaf; D. Close up of leaf, adaxial surface; E. Abaxial view of leaf; F. Close-up of leaf, abaxial surface; G. Inflorescence; H. Front view of staminate flowers; I. Lateral view of staminate flowers; J. Front view of pistillate flower; K. Lateral view of pistillate flower; L. Infructescence; M. Front and lateral view of fruits; N. Serial cross sections of an ovary from the top to the bottom. Scale bar: B, D, F, G–M=1cm, B, N = 5 mm, C, E = 4 mm. (A, G, J, K, L photographed by Y.M. Shui, B–F, H, I, M, N by S.W. Guo)