Begonia baishishanensis R. C. Hu & D. K. Tian, 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 baishishanensis R. C. Hu & D. K. Tian sp. nov.

Fig. 3 , Table 1 Chinese name: 白石山秋海棠

Diagnosis.

Begonia baishishanensis is most similar to B. danxiaensis D. K. Tian & X. L. Yu ( Tian et al. 2019) , but differs in its larger (3–21 × 2.6–20.3 cm vs. 2–13 × 1.5–13.5 cm) and thicker (vs. thinner) leaves, hairy (vs. nearly glabrous) bract margins, larger outer tepals of staminate flower (13–17 × 10–14 mm vs. 4–11 × 3–10 mm) and pistillate flower (10–13 × 11–15 mm vs. 3–9 × 4–9 mm), more (47–88 vs. 10–38) stamens, and placentae bilamellate (vs. unilamellate). The species is also similar to B. fimbristipula ( Hance, 1883) belonging to B. section Diploclininum , but mainly differs by its larger (3–21 × 2.6–20.3 cm vs. 4–13 × 4.8–8.5 cm) and thicker (vs. thinner) leaves, shorter (≤ 0.5 mm vs. ≥ 1 mm long) hairs on adaxial leaf surface, larger outer tepals of pistillate flower (13–17 × 10–14 mm vs. 8–13 × 8–10 mm) and pistillate flower (10–13 × 11–15 mm vs. 6–8 × 9–11 mm).

Type.

China. • Guangxi; Guiping City, Madong (麻垌) Town, Baishi (白石) Village (Fig. 2 ), growing on rock walls or with grasses of Danxia landform mountain, 23°42'8"N, 110°12'19"E, elev. 383 m, late flowering, April 21, 2024, Daike Tian, Jinye Zhou, Renchuan Hu TDK 5596 (holotype: CSH 0214176 ; isotypes: CSH 0214177 , 0214178 , 0214179 , CSH!) .

Description.

Herb perennial, 3–15 cm tall, monoecious, tuber spherical, usually 2–3 connected, 8–30 mm in diameter; erect stem absent or with 1 at anthesis, 0.2–4 cm long, 3–8 mm thick. Stipules long triangular, ca. 6 mm long, covered with grayish-white long rough hairs. Leaves usually 1, rarely 2 per plant, blade cordate, nearly symmetrical, 3–21 × 2.6–20.3 cm, wide side 1.4–10.1 cm, narrow side 1.2–10.1 cm; adaxially green, rarely dark green, covered with grayish-white short rough hairs, hairs usually ≤ 1 mm long, venation palmate, veins 9–10, concave; abaxially gray-green, rarely purple-red, grayish-white villous, hairs 1–5 mm long, longer (up to 4 mm) at the base of primary veins, primary veins convex, secondary veins slightly convex; lobes of leaf base valvate to acute angled or slightly overlapped, margin with few serrate and short cilia, apex acuminate or short acuminate. Petioles green, rarely red, 0.8–18 cm long, 1.2–6 mm thick, grayish-white villous, hairs up to 4 mm long, denser on the top position. Inflorescence: dichasial cyme, basal, usually 1, rarely 2 per plant, 4–40 cm long, peduncle 1.5–24 cm long, 0.8–8 mm thick, nearly glabrous, 2–15 flowers per inflorescence. Bracts light green, long triangular to nearly lanceolate, 4–11 × 1.5–5 mm, margin ciliate. Staminate flower: pedicel greenish-white with pink, glabrous, 10–19 mm long, 0.6–0.8 mm thick; flower 26–34 × 25–31 mm, tepals 4, pink, coloration even, glabrous; outer 2 ovate or oval, 13–17 × 10–14 mm; inner 2 nearly obovate or obovate-lanceolate, 11–19 × 7–9 mm; androecium nearly capitate, actinomorphic, 3–4 × 4–5 mm; stamens 47–88; filaments base fused, connate part ca. 1.5 mm long, free part 1–1.5 mm long, anthers 0.8–1 mm long. Pistillate flower: pedicel pink, glabrous, 8–13 mm long, 0.6–0.8 mm thick; flower 22–26 × 12–19 mm, tepals 3, pink, coloration nearly even, glabrous; outer 2 broadly ovate or ovate, slightly flat, 10–13 × 11–15 mm; inner 1 obovate or obovate-lanceolate, 6–12 × 3–7 mm; pistils 4–5 × 3–5 mm; styles 3, nearly free, 1.5–2 mm long; ovary 3 locular, placentation axile, placentae bilamellate. Fruit: stalk 11–20 mm long, ca. 1 mm thick, capsule 8–11 × 6–9 mm, unequally 3 - winged, larger one nearly rectangular or triangular-rectangular, 11–15 × 10–15 mm, apex nearly obtuse or pointed; smaller wings sickle-shaped, 1–2 × 7–16 mm.

Phenology.

Flowering March to April, fruiting April to May.

Etymology.

The epithet “ baishishanensis ” refers to Baishishan, a mountain name of Guiping City and the type locality of this species. The Chinese name is given as “ 白石山秋海棠 ”.

Distribution and habitat.

One population including four subpopulations of B. baishishanensis are found on rock walls or grass, or in rock crevices of Danxia landform cliff of Baishishan of Guiping City, Guangxi, China (Fig. 2 ).

Conservation status.

The new species is only found in the type locality, the extent of occurrence is about 2 km 2 and the area of occupancy is less than 2 km 2, and has only one population (<2000 mature individuals, and few seedlings). Due to its unique habitat and negative influence by tourism, its living space is shrinking, currently it is assessed as Critically Endangered (CR) (B 1 ab (i – v) + 2 ab (i – v )) following Guidelines for Using the IUCN Red List Categories and Criteria ( IUCN 2024). Therefore, B. baishishanensis should be suggested to be included in the future List of China National Protected Wild Plants. However, further investigation is necessary on its actual distribution area and the number of populations and individuals.

Additional specimens examined.

China. • Guangxi: Guiping City, Madong Town, Baishi Village , growing on rock wall or grass of Danxia landform mountain, 23°42'8"N, 110°12'19"E, elev. 383 m, peak flowering, March 25, 2024, Renchuan Hu Xincheng Qu, TDK 5596 ( CSH!) .

Figures

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

Figture 3. Begonia baishishanensis R. C. Hu & D. K. Tian A habitata in Baishishan landform in Guiping of Guangxi B, C habit and plants in late flowering D individual plants showing size variation E abaxial blade surface of red leaf individual F abaxial leaf surface and petiole showing indumentum G adaxial leaf surface H bract I front view of staminate flower J front view of pistillate flower K cross-section of ovary showing bilamellate placentae L young fruits showing shape variation of large wings. (Photos by Daike Tian).