Begonia medogensis Li et al. (2018: 14)

Chen, Wen-Hong, Tian, Dai-Ke, Radbouchoom, Sirilak, Xiao, Yan, Cong, Yi-Yan, Guo, Shi- Wei & Shui, Yu-Min, 2018, Miscellaneous notes on Begonia medogensis (Begoniaceae), Phytotaxa 381 (1), pp. 100-106 : 101-104

Begonia medogensis Li et al. (2018: 14) .

TYPE:— CHINA. Tibet, Medog County, Xiaohua Jin, Jianwu Li, Xilong Wang & Chengwang Wang 19331 (holotype: HITBC!, isotype: HITBC!, PE!, K!). Figure 2A–I and 3

— Begonia hatacoa auct. non Buch.-Ham. ex Don (1825: 223), Gu et al. in: Wu, et al. (2007: 157 in clavi).

Similarity:—The species is mostly similar to Begonia coptidimontana Wu (1995: 251) ( Fig. 2J–Q ) in Begonia sect. Diploclinium ( Lindley 1846: 319) de Candolle (1859: 129) in the cane-like habitat and leaf morphology, but differs in its hairy stems and petioles (vs glabrous), nearly entire of leaf margin (vs denticulate), slightly oblique leaf base (vs extremely oblique), caudate leaf top (vs acuminate), obcordate anthers (vs obovate) and retuse contectives (vs slight protruding and round). It is also somewhat similar to B. hatacoa in sect. Platycentrum in leaf shape ( Fig. 2R–Y ), but differs in its long and highly-branched erect stem (vs short and less branched), caudate leaf apex (vs acuminate), obcordate anthers (vs oblong) and retuse contectives (vs protruding and acute).

Herb evergreen, cane-like or shrub-like, nearly erect or upward inclined, 50–100 cm tall; rhizome short, 3–5 cm long, 0.5–1.2 cm thick. Stem brownish red, much branched, whitish hairy when young, brown hairy when matured; node clearly expanded 3–10 mm thick, internode 5–15 cm long. Stipule long triangular, 5–16 × 2–5 mm, margin entire, apex acuminate, brown hairy on back. Petiole brownish red, 1–9 cm long, 0.6–2 mm thick, with very short brownish pubescent. Leaves alternate; blade asymmetric, elliptic or lanceolate, 3.5–11 × 1.4–5 cm, slightly rugose, adaxially green and glabrous, abaxially pale green, hairy on veins when young and light brownish pubescent or nearly glabrous when matured; primary veins 5–7, secondary veins branching dichotomously and not clear on adaxial surface, tertiary veins reticulate and not clear on adaxial surface and slightly clear on abaxial surface; leaf base shallowly cordate to nearly rounded or rarely peltate, slightly oblique; leaf margin nearly entire to sparsely denticulate, with very short red hispid at the end of secondary primary veins; leaf apex caudate. Inflorescence dichasium, 1–2, nearly terminal, 5–6 cm long; peduncle red, pubescent to nearly glabrous, 2–4 cm long, about 1 mm thick; bract and bracteoles greenish, caducous, long triangular, 3–8 × 1–3 mm, margin entire, apex acuminate. Staminate flower: pedicel red, 2–2.5 cm long, glabrous; corolla 2–2.5 × 2–2.3 cm, tepals 4 (rarely–6), glabrous, outer tepals 2, pinkish-white, ovate, 1–1.5 × 0.8–1.5 cm; margin entire, apex obtuse or rounded; inner tepals 2, white to nearly white, oblong or elliptic, 0.8–1.3 × 0.5–0.9 cm, base cuneate, margin entire, apex obtuse or rounded; stamens 40–52; filament 0.8–1.2 mm long, fused column 1–1.5 mm long; anther yellow, 0.7–1 mm long, obcordate, with two longitudinal pore slits, contective retuse. Pistillate flower: pedicel 1.4–1.8 cm long, red, glabrous; tepals 5, nearly white or pink to gradually white from outer to inner ones, glabrous; outer tepals 4, ovate, 0.6–1.2 × 0.4–1 cm, margin entire, apex obtuse or rounded, base cuneate to rounded; inner tepal 1, ovate to broadly ovate, smaller, 0.5–1.0 × 0.2–0.4 cm, margin entire, apex obtuse, base cuneate to rounded; ovary green to pinkish, glabrous; placentae axile, 2-locular, 2 placentae per locule; styles 2, free; stigmas bifid, spirally twisted. Fruit capsule-like, green to red, nodding, unequally 3 wings; large wing oblong, 12–18 × 6–8 mm; small wings 2, narrowly obovate, 2–2.5 × 6–8 mm. Seeds numerous.

Phenology:— Flowering September–December, fruiting October–January.

Habitat and distribution:— This species grows along the riverside or near stream under the secondary forest of the moist valleys with 600–1500 m elevation. It is found in Motuo (=Medog) county, Xizang (= Tibet), China, and in Putao district, Kachin state, Myanmar.

Conservation status:— Currently, Begonia medogensis is only observed from several locations with small populations each consisting of sparsely isolated individuals.Totally, there are three localities known (Duba, Renqinbeng, and Beibeng population) in Motuo county, Tibet of China. In Myanmar, two populations have been so far observed with about 100 individuals (data provided by Yunhong Tan from Xishuang Banna Tropical Botanical Garden, Chinese Academy of Sciences). Although further survey is needed on its actual distribution and population size, this species should be considered to be “Near Threatened” (NT) based on the current data with a narrow distribution range, small and severely fragmented populations possibly continuing decline due to habitat disturbance such as current road construction in Motuo county according to the IUCN Red List Categories and Criteria ( IUCN Standards and Petitions Subcommittee 2017).

Additional examined specimens:— CHINA. Xizang (Tibet): Motuo (Medog) county, from Damu to Zhuba , 4 November 1982, Bo-Sheng Li & Shu-Zhi Cheng 1662 (01392562 PE!, 01392563 PE!, 01392564 PE!, 01392565 PE!, 01392566 PE!) ; the same county, from Zhuba to Daguo Bridge , 9 January 1983, Bo-Sheng Li & Shu-Zhi Cheng 2451 (01392567 PE!, 01392568 PE!, 01392560 PE!, 01392570 PE!) ; the same county, from Mati community, 20 January 1983, Bo-Sheng Li & Shu-Zhi Cheng 2640 (01392571 PE!, 01392572 PE!, 01392573 PE!) ; the same county, Renqinbeng , 24 January 1983, Bo-Sheng Li & Shu-Zhi Cheng 3416 (01392549 PE!, 01392550 PE!, 01392551 PE!, 01392552 PE!) ; the same county, Renqinbeng , 24 January 1983, Bo-Sheng Li & Shu-Zhi Cheng 3531 (01392567 PE!, 01392568 PE!, 01392560 PE!, 01392570 PE!) ; the same county, nearby Buqiong Lake , 12 March 1983, Bo-Sheng Li & Shu-Zhi Cheng 2953 (01392574 PE!, 01392575 PE!, 01392576 PE!) ; the same county, Beibeng, Xijiang Lake , 4 May 1983, Shu-Zhi Cheng, Zhi-Cheng Ni, Bo-Sheng Li 4876 (01392559 PE!, 01392560 PE!, 01392561 PE!) ; the same county, Beibeng , under forest, 29°14’07’’ N, 95°10’51.5’’ E, elev. 1500 m, 4 September 2009, Southeast Tibet Expedition, Xiao-Hua Jin, Bing Liu, Xu Quan, Miao Sun, Wei Zhao SET-ET 1157 (2293662 PE!, 2293663 PE!) ; the same county, from Motuo town to Beibeng community, on the rock surfaces along the riverside in the forest, elev. 670 m, 2 August 2016, Yu-Min Shui, Wen-Hong Chen, Jin-Xiu Li B 2016-218 ( KUN!) ; the same county, between Hanmi and Beibeng , 19 October 2010, Yi-Yan Cong 20101019 (CSH) ; the same county, nearby a hydropower station close to Motuo town , under forest, 29°19’46’’N, 95°20’32’’E, elev. 1030 m, 28 September 2017, in early flowering, Dai-Ke Tian, Yan Xiao, Xin Zhong, Li-Zhi Tian, TDK-3413 ( CSH!) ; the same county, Beibeng, Jiangxin , under forest, 29°13’27’’N, 95°07’45’’E, elev. 680 m, 01 October 2017, in early flowering, Dai-Ke Tian, Yan Xiao, Xin Zhong, Li-Zhi Tian, TDK-3432 ( CSH!) ; the same county, Beibeng , near a hydropower station, under forest, 29°14’32’’N, 95°10’19’’E, elev. 830 m, 01 October 2017, Dai-Ke Tian, Yan Xiao, Xin Zhong, Li-Zhi Tian, TDK-3436 (0149383 CSH!) . MYANMAR. Kachin State: Putao district , in tropical montane forest, 27°37’15’’N, 97°53’14’’E, elev. 900 m, 1 December 2016, in flowering, Myanmar Exped. M 0727 ( HITBC!) .

Note:— The combination of 5-tepaled corolla, 2-locular ovary and rhizomatous habit indicates that the B. medogensis is obviously a member of Begonia sect. Platycentrum ( Doorenbos et al. 1998, Shui et al. 2002, Moonlight et al. 2018). In the Pan Himalaya region ( Hong 2016), there are very few species with erect stems in the same section, such as Begonia gungshanensi s Wu (1995: 270), B. flaviflora , B. hatacoa , B. palmata , and B. sikkimensis , but these are all easily distinguished from this new species in leaf morphology, unbranched or less branched stems ( Smith et al. 1986, Shui & Chen 2017). Therefore, this species is unique in Tibet and its adjacent regions.

Figures

FIGURE 2. Morphology of Begonia medogmensis (A–I), B. coptidimontana (J–Q) and B. hatacoa (R–Y). A. Habit; B. Adaxial leaf surface (scale bar, sb = 3 cm); C. Abaxial leaf surface (sb = 3 cm); D. Male flower (sb = 1 cm); E. Female flower (sb = 1 cm); F. Close-up of stamen cluster, front view (sb = 1 cm); G. Close-up of stamen cluster, side view (sb = 1 cm); H. Transitional section of ovary (sb = 2 cm); I. Side view of female flower (sb = 1 cm); J. Habit; K.Adaxial leaf surface (sb = 3 cm); L. Abaxial leaf surface (sb = 3 cm); M. Male flower (sb = 5 mm); N. Female flower (sb = 5 mm); O. The close-up of anthers, front view (sb = 1 mm); P. Transitional section of ovary (sb = 2 mm); Q. Side view of ovary (sb = 5 mm); R. Habit; S. Adaxial leaf surface (sb = 2 cm); T. Abaxial leaf surface (sb = 2 cm); U. Male flower (sb = 5 mm); V. Female flower (sb = 5 mm); W. Close-up of anthers, front view (sb =1 mm); X. Transitional section of ovary (sb = 2 mm); Y. Side view of female flower (sb = 5 mm).

FIGURE 3. Begonia medogmensis JianW.Li,Y.H.Tan & X.H.Jin A. Lower part of mature plant showing short rhizome and erect stems; B. Flowering branch; C. Male flower; D. Head-shaped stamen cluster and single stamen; E. Female flower with five tepals; F. Two branched styles and stigmas; G. Fruit; H. Transitional section of ovary; I. Stipules; J. Bracts and bracteoles (Drawn by Mrs.Yan-Xin Piao based on photos taken by Dai-Ke Tian from the wild plants).