Begonia satelloides Y.M.Shui, H.Q.Nguyen & 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 : 96-97

Begonia satelloides Y.M.Shui, H.Q.Nguyen & W.H.Chen sp. nov. ( Fig. 3 )

The species is similar to B. balansana Gagnepain in the lanate indumentum on the abaxial leaf surface, 6‒8-loculed ovary and spheroidal fruit, but differs in its cylindrical (vs grooved) petiole, leaf shape (broadly ovate leaves vs narrowly oblong or elliptic), and the fruit appendices (wings vs horns).

Type:— VIETNAM. Vinh Phuc province: Tam Dao Natural Reserve, on roadside in the secondary forests, 21°28′26″N, 105°97′57″E, elev. 1200 m, 25 October 2012, introduced into Kunming Botanical Garden, in flower in September 2016, Y. M. Shui et al. CK373a (holotype, KUN!, barcode 0756800).

Herb, shortly rhizomatous, without erect stem. Stipules caducous. Leaves 2‒6, alternate; petioles 8‒28 cm long, cylindrical, densely pubescent; leaf blade ovate or broadly ovate, 7‒27 × 5‒15 cm, membranous or chartaceous, margin superficially repand, apex acute, base obliquely cordate; adaxially dark green, glabrous; abaxially pale green, densely pubescent on veins; venation palmate, dictyogenous, 3‒6-veined. Inflorescence cyme, peduncle (8‒) 12‒23 cm long, ferrugineous-red, glabrescent or slightly pubescent. Staminate flower: tepals 4, pink, glabrous; outer 2, widely ovate, 7‒9 × 4‒6 mm, inner 2 narrowly elliptic, 6‒8 × 2‒2.2 mm. Pistillate flower: petals 4 or 5, pink, glabrous; outer 2, widely ovate, 7‒8 × 4‒6 mm, inner 2 narrowly elliptic, 6‒8 × 1.5‒1.9 mm; ovary dark pink, spheroidal, 6‒13 mm long, 2‒16 mm in diam., 6‒8-loculed, sparsely covered with yellow or red short pubescence; styles 6‒8, free; stigma spirally once twisted; placentation axile, placentas bifid per ovary locule. Fruits spheroidal, baccate, nodding, 21‒22 mm long, glabrous, equally 6‒8-winged; wings slightly triangle, 4.2‒5.5 mm wide, 14‒15 mm high, apex acute.

Phenology:—Flowering August‒October, fruiting September‒November.

Habitat and ecology:—The new species is currently known only from Tam Dao in Vietnam. It usually grows in shaded and humid environments in evergreen broad-leaved forests.

Etymology:—The epithet refers to the shape of the cross section of the ovary with its 7‒8 radiate wings, and which is similar to the shape of a star-like artificial satellite ( Fig. 3H‒M ).

IUCN category:—This new species grows on the slope nearby rough roads in Tam Dao Natural Reserve. Two recent surveys have shown that there are totally about 40 mature individuals restricted in a single population ( Fig. 1 ). Although the plants are located in a protective reserve, the population’s future is unstable, due to their roadside habitat and the ongoing pressures of tourism. Thus, we provisionally considered B. satelloides as the “Critically Endangered [B1ab (iii) + 2ab (iii)]” species according to the Guidelines using the IUCN Red List Category and Criteria ( IUCN 2017).

Additional examined specimens:— VIETNAM. Vinh Phuc province, Tam Dao , 21°28′26″N, 105°97′57″E, elev. 1200 m, 25 October 2012, H. Q. Nguyen, H. T. Nguyen, Y. M. Shui, Y. K. Sima, S. X. Yang, Z. Zhou, J. Liu CK 373 ( KUN!, CPC!) ; ibid., elev. 1230 m, 9 April 2016, Y. M. Shui, W. H. Chen, C. Liu, L. Chen, H. Q. Nguyen, H. T. Nguyen, N. B. Tu, N. Q. Chuong CK 0947 ( KUN!, CPC!) .

Note:—During the Sino-Vietnam joint survey of North Vietnam in 2012, the authors (H.Q. Nguyen, H.T. Nguyen, Y.M. Shui) collected this unknown species of Begonia with fruits in Tam Dao National Park nearby Hanoi. An author (H.Q. Nguyen) went to the field to observe its flowers on a summer in 2014, but missed the flowering phase because of the dry season. In September 2016, we observed the flowers from individuals growing in the greenhouse at the Kunming Botanical Garden ( Fig. 3 ).

The new species is very unusual among Asian Begonia in its baccate fruit with 6–8 wings. It is more similar to B. balansana in habit, locule number of the ovary and fruit shape, but differs mainly in the fruit having wings instead of horns. Besides, it is similar to B. handelii in its ovate leaf blades and spheroidal fruits, but mainly differs in number of ovary locules, styles and stigmas. Detailed illustrations and images of B. balansana and B. handelii have previously been published ( Tebbitt 2003, Shui & Chen 2017, Hughes et al. 2018) allowing comparison with the new species. Table 2 shows the detailed differences among the above three species.

In North Vietnam and South China, besides B. balansana , the new species seems to be related to B. bambusetorum Nguyen, Shui & Chen (2018: 69) in its non-limestone habitat, habit, leaf shape and flower color, but differs in having baccate fruits instead of capsules ( Chen et al. 2018), a similar case as described for the above species complex ( B. gulinqingensis , B. hahiepiana , and B. pendens ) likely occurs with an evolutionary shift between capsules and baccate fruits. Recent molecular study has also shown that Begonia sect. Platycentrum not only has 2‒8-loculed ovary but also baccate and capsular fruits ( Moonlight et al. 2018, Shui et al. 2019). So, their systematic affinity deserves further exploration and confirmation within B. sect. Platycentrum in the future.

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 3. Begonia satelloides Y.M.Shui, H.Q.Nguyen & W.H.Chen sp. nov. (A, H, L from H.Q. Nguyen et al. CK373; B–K from holotype) A. Plant and habitat (A1: Young leaf; A2: Leaf; A3: Leaf Base; A4: Abaxial leaf surface showing the prominent venation); B. Front view of male flower; C. Lateral view of male flower; D. Stamens; E. Front view of female flower; F. Lateral view of female flower; G. Styles; H. Nearly mature fruits; I. Lateral view of young fruit; J. Front view of young fruit; K. Rear view of young fruit; L. Rear view of fruit; M. Cross section of young fruit, sectioned in the middle of the organ. Scale bars:A = 4 cm, A1–A4 = 1 cm, B, C, E, F = 5 mm, D, G = 2 mm, H–M = 1 cm. (A, H, L and M photographed by Y.M. Shui; A1–4 by H.Q. Nguyen; B–G and I–K by S. Radbouchoom)