Begonia pseudoedulis D.K.Tian, X.X.Feng & R.K.Li, 2021

Feng, Xin-Xin, Xiao *, Yan, Liu, Zhi-Xian, Li, Ren-Kun, Wei, Dan & Tian, Dai-Ke, 2021, Begonia pseudoedulis, a new species in Begonia sect. Platycentrum (Begoniaceae) from southern Guangxi of China, PhytoKeys 182, pp. 113-124 : 113

Begonia pseudoedulis D.K.Tian, X.X.Feng & R.K.Li sp. nov.

Figs 1 , 2 , 3 Chinese name: 假食用秋海棠

Type.

China Guangxi, Shangsi County (上思县), Shiwanshan (十万山), 21°58'4.71"N, 108°16'50.05"E (Fig. 4 ), 163 m alt., near a stream under the broad leaf forest, at late period flowering, October 2020, X. X. Feng, Z. X. Liu, & R.K. Li, FXX201001 (holotype: CSH0185896, CSH!; isotypes: CSH! & SYS!) .

Diagnosis.

The new species shows high resemblance to both B. edulis and B. dielsiana from the same section (sect. Begonia Platycentrum ) in their stout and creeping rhizome, erect stem at anthesis, asymmetric ovate and chartaceous leaf blade, palmate venation, dichasial cyme, four tepals of staminate flowers, unequally 3-winged capsules. However, it differs from the latter two mainly by its shorter (vs. taller) plants, variation (variegated more than pure green vs. green or dark-green for B. edulis and pure green for B. dielsiana ) in leaf color, hairy (vs. glabrous or nearly so) petioles and red hairs (vs. glabrous or nearly so) on abaxial surface of outer tepals, stable five (vs. usually five and rarely six for B. edulis , and more six than five for B. dielsiana ) tepals of pistillate flowers.

Description.

Perennial evergreen herb, monoecious, 30-50 cm tall. Rhizome stout and creeping, ca. 10-12 cm long and 10-15 mm in diameter, internodes obvious and crowded; erect stem only at anthesis, usually reddish-brownish, rarely green, sparsely pilose. Stipules membranous, triangular, reddish or green, glabrous. Leaves 6-8 basal and 2-3 aerial, petiole pale- to reddish-green, 18-50 cm long, 5-10 mm thick, densely red pilose, 3-5 mm long at young stage and then sparsely short reddish-brownish or gray hairs in mature; leave blade variable in shape and coloration, usually widely ovate, 12-23 × 9-22 cm, adaxially dark-green along main veins or evenly green, rarely white spotted, puberulent, abaxially purple-red along veins or evenly green, subglabrous except main veins, base strongly oblique-cordate, margin triangularly denticulate to shallowly lobed, apex caudate. Venation palmate, primary veins 7-8, adaxially slightly concave, abaxially convex. Inflorescences arising from erect stem at anthesis, dichasial cymes branching only once, peduncle 16-23 cm long, red short strigose, flowers unisexual, 5-8 flowers per inflorescence; bracts membranous, oblong triangular to widely ovate, reddish-brownish, 8-15 × 4-8 mm, glabrous. Staminate flower: pedicels pink, 2.0-2.5 cm long, hairy nearly same as peduncles; tepals 4, white or nearly so, outer 2 broadly ovate, 18-23 × 17-22 mm, middle part thicker, adaxially concave, abaxially convex, red short strigose, veins distinct, apex obtuse, margin entire; inner 2 nearly obovate, ca. 18 × 14 mm, glabrous; androecium spheroid, ca. 11 mm across; stamens numerous, ca. 4-5 mm long; filaments fused at base, anthers yellow, clavate, base cuneate, ca. 2 mm long. Pistillate flower: pedicels pink, 2.0-2.5 cm long, hairy nearly same as peduncles; tepals 5, white or nearly so, irregularly suborbicular, fan-shaped or broadly ovate, sub-equal, 16-19 × 15-17 mm, abaxially sparsely red short strigose, apex obtuse; ovary yellowish-green, trigonous-ellipsoid, 12-14 × 8-9 mm (wings excluded), red hispidulous; 2-loculed, placentation axile, placentae bifid per locule; styles 2, fused at base, yellow, ca. 7-9 mm long; stigma U-shaped, spirally twisted. Capsules nodding, trigonous-ellipsoid, ca. 18 × 8-10 mm (wings excluded), yellowish-green, red hispidulous; wings 3, unequal, abaxial wing semicircle-shaped or rectangular, ca. 15 mm long; lateral wings narrow, 3-4 mm long.

Additional specimens examined.

China Guangxi: Fangchenggang District (防城港区), Dongzhong Town (峒中镇), Nameng Village (那蒙村), roadside of S325, near stream under bamboo forest, 21°38'32.63"N, 107°35'48.91"E, elev. 380 m, 1 April 2015, Dai-Ke Tian , Li-Zhi Tian , TDK2423 (CSH!); Dongzhong Town (峒中镇), Dakeng Village (大坑村), Maan’ao (马鞍坳), 21°38'25.32"N, 107°39'34.40"E, elev. 650 m; Wuming County (武鸣县), Liangjiang Town (两江镇), Daming Mountain Nature Reserve (大明山保护区), 23°25'38"N, 108°27'35"E, elev. 550 m, Dai-Ke Tian, Yan Xiao, Yi Tong & Li-Zhi Tian, TDK3008 (CSH!); Wunming County , Liangjiang Town , 23°26'19.74"N, 108°24'31.92"E, Ya-Hong Gao TDK4001 (collected at Shanghai Chenshan Botanical Garden from introduced plants)

Distribution and habitat.

Currently known from four localities with elev. 160-650 m. (Fig. 4 ). It grows in shaded environment along the stream or near waterfall under the broad-leaved forest.

Phenology.

Flowering August-October, fruiting September-November.

Etymology.

The specific epithet " Begonia pseudoedulis " refers to its similarity to B. edulis , because both are easily confused based on appearance when the inflorescences and flowers are invisible.

Conservation status. Only four populations with under 1000 estimated individuals have been found so far in three counties of Guangxi. Each population consisting of approximately 20-300 individuals is distributed in no more than 200 m2 area. The population size is prone to decrease by illegal collection for medicinal and ornamental uses. Considering the disturbance of human activities and narrow distribution, B. pseudoedulis is currently assessed as "Near Threatened" (NT) according to the IUCN Red List Categories and Criteria (IUCN, 2019).

Molecular Analysis

The ITS data set containing 40 accessions represented 26 species, four main sections of Begonia in China and one section from Africa (Table 1 ). The aligned matrix of ITS region was 664 bp. The result of Bayesian inference analysis was shown in Fig. 5 . The sect. Begonia Platycentrum appeared monophyletic with a high Bayesian posterior probability (bpp = 0.97). The putative new species was a monophyletic lineage (bpp = 1) and sister with B. dielsiana and B. emeiensis . Begonia edulis with the highest morphologic resemblance of B. pseudoedulis formed another clade.

Nodes with bpp <0.50 have been collapsed. Sectional placement of taxa is indicated by the following abbreviations: Aug: Augustia , Coe: Coelocentrum , Dip: Diploclinium , Pla: Platycentrum , Rei: Reichenheimia . The numbers after the species names indicate different populations. The samples of new species are indicated in bold letters.

Figures

Figure 1. Begonia pseudoedulis A habitat B adaxial leaf blade C abaxial leaf blade D, E inflorescences F staminate flower (abaxial) G staminate flower (adaxial) H stamen I pistillate flower (adaxial) J pistillate flower (abaxial) K ovary and stigma L cross section of ovary M capsule (Illustration drawn by Yunxiao Liu).

Figure 2. Habitat and morphology of Begonia pseudoedulis A habitat B creeping rhizome C stipule D petiole showing hairs E mature leaf blade (adaxial) F juvenile leaf blade (adaxial) G, H mature leaf blade (abaxial) I inflorescence J bracts K erect stem at anthesis L front view of staminate flower M back view of staminate flower N stamens O front view of pistillate flower P back view of pistillate flower Q ovary with styles and stigmas R cross section of ovary S, T Immature capsule (different views) U dry capsule showing abaxial wing V dry capsule showing lateral wings.

Figure 3. Variation in leaf morphology of different populations of Begonia pseudoedulis A-E the population from Fangcheng, Fangchenggang, Guangxi (A, B mature plants C-E juvenile individuals showing dense hairs on petioles) F-H wuming, Nanning, Guangxi I, J daxin, Chongzuo, Guangxi (photos A-E, J by Dai-Ke Tian F-H by Jun Liu from Zhejiang University; I by Chen-Yang Zhao from Daxin County of Guangxi). Note: The population from Daxin, Chongzuo (I, J) is only recognized by morphology without molecular evidence.

Figure 4. Distribution of Begonia pseudoedulis and the allied B. edulis and B. dielsiana.

Figure 5. Bayesian inference of the phylogenetic position of the newly described B. pseudoedulis within sect. Begonia Platycentrum based on nuclear ITS sequences.