Begonia angustibracteata D. K. Tian & R. C. Hu, 2025

Hu, Renchuan, Zhou, Jinye, Zhao, Ziyi, Lai, Kedao, Wu, Yannong & Tian, Daike, 2025, Two new tuberous species of Begonia (Begoniaceae) from Guangxi, China, PhytoKeys 256, pp. 119-129 : 119-129

Begonia angustibracteata D. K. Tian & R. C. Hu sp. nov.

Fig. 1 , Table 1 Chinese name: 狭苞秋海棠

Diagnosis.

The new species is mostly similar to the green-leaved individuals of B. fimbristipula Hance ( Hance 1883) , but differs mainly by its leaves sparsely hairy (vs. densely hairy), with a bracteole at the top of the pistillate flower pedicel (vs. without), larger (10–12 × 12–13 vs. 6–8 × 9–11 mm) outer tepals of pistillate flower, placentae unilamellate (vs. bilamellate), and later flowering (June – July vs. April – May).

Type.

China. • Guangxi: Guiping (桂平) City, Xishan (西山) Town, Bitan (碧滩) Village (Fig. 2 ), near streams or on wet or slightly dry rock walls, 23°25'45"N, 109°53'9"E, elev. 38 m, dried fruits of the previous year, April 21, 2024, Daike Tian, Jinye Zhou, Renchuan Hu TDK 5598 (holotype: CSH 0214187 ; isotypes: CSH 0214184 , 0214185 , 0214186 , CSH!) .

Description.

Herb perennial, 2–20 cm tall, monoecious, tuber spherical, 8–25 mm in diameter. Leaves usually 1 per plant, sometimes 2 (more common in large plants); membranous, slightly asymmetric to near symmetrical, cordate, oval or ovate, 5–38 × 4–32 cm, wide side 2.2–17.5 cm, narrow side 2–15 cm, adaxially green, covered with very short rough hairs, hairs ≤ 0.5 mm, venation palmate, veins 10–11 (– 12), concave; abaxially grayish-green, veins convex, covered with grayish-white villous, hairs 1–5 mm long, longer at the base of primary veins; margin heavily serrate and short grayish-green hairy, hairs ca. 1 mm long, apex acute and often coarsely toothed. Petioles green, light green or pink, 1.5–20 cm long, 1.5–9 mm thick, light green longitudinal spotted and grayish-white villous, hairs ≤ 6 mm long, or sparsely pale-white hairs on the upper of petioles; petiole base grooved. Inflorescence: dichasial cyme, 1 per plant, occasionally 2, 5–33 cm long; peduncle 3–23 cm long, 2–6 mm thick, reddish-brown, glabrous, 3–10 flowers per inflorescence. Bracts nearly persistent, nearly linear, 3–6 × 1–2 mm, basal bracts with 3 red longitudinal stripes, upper bracts with red midribs. Staminate flower: pedicel light green, usually gradually turning pink downwards, glabrous, 10–50 mm long, 1 mm thick; flower 16–23 × 18–25 mm; tepals 4, glabrous, outer 2 ovate, 8–12 × 8–12 mm, adaxially pink, slightly light green on the top edge, depressed and slightly thick in central part; abaxially color slightly lighter, nearly pinkish-white; inner 2 narrowly oblanceolate, pinkish-white, 9–12 × 4–5 mm, lighter and thinner than outer tepals; androecium nearly capitate, actinomorphic, 1.5–2 mm long, 2–3 mm wide; stamens 27–45, filaments basally fused, stamen column nearly 2 mm long, filaments and anthers nearly 1 mm long, fragrance pleasant. Pistillate flower: pedicel light green, glabrous, 20–24 mm long, ca. 1 mm thick, with a bracteole on the top of pedicel or below ovary, 4–5 × ca. 1.5 mm; flower 13–21 × 12–14 mm, tepals 3, glabrous, outer 2 ovate, pinkish-white, slightly flat, the middle and lower parts gradually turning dark pink, 10–12 × 12–13 mm; inner 1 oblanceolate; pistils 4–5 × 3–4 mm, styles 3, nearly free, ca. 2 mm long; ovary 3 locular, placentation axile, placentae unilamellate. Fruit: stalk 10–28 mm long, ca. 1 mm thick; capsule 6–9 × 4–6 mm, unequally 3 - winged, large one nearly triangular or rectangular-triangular, 10–18 × 9–19 mm, lateral wings sickle-shaped, 1.5–3 × 8–10 mm.

Phenology.

Flowering June – July, fruiting July – August.

Etymology.

The epithet “ angustibracteata ” refers to the narrow bracts of this new species. The Chinese name is given as “ 狭苞秋海棠 ”.

Distribution and habitat.

The new species has been found only in three places restricted to Guiping City and Hengzhou City of Guangxi (Fig. 2 ). It grows on rock cliffs or in shaded places of valleys at an altitude of 30– 300 m.

Conservation status.

The new species has been found only in three places of Guiping and Hengzhou City (Fig. 2 ), the extent of occurrence is about 210 km 2 and the area of occupancy is about 12 km 2. Although one of three locations has a large number of individuals (> 10000 mature individuals, and many seedlings) and new populations will be possibly discovered in other places in the future. The conservation status of this species is assessed as Endangered (EN) (B 1 ab (i-v) + 2 ab (i-v )) due to possibly partial loss of habitats caused by road construction or maintenance, following Guidelines for Using the IUCN Red List Categories and Criteria ( IUCN 2024).

Additional specimens examined.

China. • Guangxi: Guiping City, Xishan Town, Bitan Village , near streams on wet or slightly dry rock walls, or in crevices, 23°25'45"N, 109°53'9"E, elev. 38 m, flowering, July 26, 2023, Renchuan Hu, Xincheng Qu 450881230726019 ( GXMI!) ; • ibid., 23°25'58"N, 109°53'23"E, elev. 57 m, few dried fruits of the previous year, April 21, 2024, Daike Tian, Jinye Zhou, Renchuan Hu TDK 5599 ( CSH!) . • Guiping City, Jiangkou (江口) Town, Litang (理塘) Village, growing on rock wall or in crevices between rocks of Danxia landform, 23°40'57"N, 110°13'44"E, elev. 299 m, April 21, 2024, few dried fruits of the previous year, Daike Tian, Jinye Zhou, Renchuan Hu TDK 5601 ( CSH!) ; • Hengzhou (横州) City, Zhenlong (镇龙) Town, growing on wet rock wall or in rock crevices, along a river valley in Jiulong Waterfall Group National Forest Park (九龙瀑布群国家森林公园), 23°3'23'N, 109°13'39"E, elev. 264 m, few dried fruits of the previous year, April 25, 2024, Daike Tian, Jinye Zhou, TDK 5639 ( CSH!) ; • ibid., 23°3'0"N, 109°13'39"E, elev. 237 m, without flower, April 25, 2024, Daike Tian, Jinye Zhou, TDK 5642 ( CSH!) .

Figures

Figure 1. Begonia angustibracteata D. K. Tian & R. C. Hu. A habitat and habit B large stipule (left corner) and small (lower right) individuals C, D portion of leaf, adaxial (C) and abaxial (D) surface E inflorescence showing flowers F peduncle showing basal bracts G bracts, abaxial views H – J front (H), back (I) and side (J) views of staminate flower K front view of pistillate flower L side view of ovary showing a bracteole at arrow M cross-section of ovary showing placentae N side view of fruit O side view of dried fruits showing dorsal wing P adaxial view of dried fruit. (Photos by Daike Tian)

Figure 2. Distribution of Begonia angustibracteata (black triangle) and B. baishishanensis (black dot) in Guangxi, China.