Research Article |
Corresponding author: Xiao-Feng Huang ( 1037758218@qq.com ) Corresponding author: Dai-Ke Tian ( dktian@cemps.ac.cn ) Academic editor: Jan Wieringa
© 2022 Xin-Xin Feng, Xiao-Feng Huang, Yu-Ni Huang, Zhi-Xian Liu, Ren-Kun Li, Jin-Ye Zhou, Wei Guo, Xiao-Yan Chen, Dai-Ke Tian.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Feng X-X, Huang X-F, Huang Y-N, Liu Z-X, Li R-K, Zhou J-Y, Guo W, Chen X-Y, Tian D-K (2022) Begonia parvibracteata, a new species in Begonia sect. Platycentrum (Begoniaceae) from Guangxi of China, based on morphological and molecular evidence. PhytoKeys 214: 27-38. https://doi.org/10.3897/phytokeys.214.90004
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The previously reported begonias in a limestone forest of Guangxi mainly belong to Begonia sect. Coelocentrum Irmscher. In this article, we described and illustrated a new species in sect. Platycentrum (Klotzsch) A.DC., Begonia parvibracteata X.X.Feng, R.K.Li & Z.X.Liu, which was discovered in a karst forest of south-western Guangxi. The begonia shows high morphological similarity to B. subhowii S.H. Huang and B. psilophylla Irmscher, but differs from the latter two in its narrower oblique-ovate asymmetric leaf blade, 4 (occasionally 6) tepals of pistillate flower and smaller membranous inflorescence bracts. Molecular phylogenetic analysis, based on ITS sequence data, supports the new species as monophyletic and distinct from B. subhowii and B. psilophylla. Considering its narrow distribution and the disturbance of human activities, the conservation status of new taxon is evaluated as “Vulnerable” (VU B1, B2 ab (i, iv, v), D2) according to the IUCN Red List Categories and Criteria.
ITS, morphology, new taxon, southern China, taxonomy
According to the latest report, China’s wild begonias have already increased to 239 species (
In Guangxi, only 11 species belong to B. sect. Platycentrum (Klotzsch) A.DC., and six of which are widespread in south and southeast China: B. circumlobata Hance, B. edulis Lévl., B. handelii Irmsch., B. hemsleyana Hook.f., B. longiciliata C.Y.Wu and B. longifolia Blume. Only five species of B. sect. Platycentrum are endemic to Guangxi, including B. tsoongii C.Y.Wu (
An unknown Begonia taxon with reproductive organs was collected from Guangxi during our field survey and plant collection in May 2020 and October 2021, respectively. The begonia definitely belongs to B. sect. Platycentrum, but differs markedly from the reported 11 begonias of the same section in Guangxi. After further detailed morphological observation, morphological comparison with similar species and molecular analysis, it is confirmed as a new species in Begonia sect. Platycentrum.
Morphological characters were observed and measured from fresh samples in the field. Morphological comparisons with similar taxa were undertaken by consulting the literature, examining herbarium (IBK and IBSC) specimens and observing living collections cultivated in the nursery of Enshi Dongsheng Plant Development Co. Ltd. The specimens were deposited at the
South China Botanical Garden (
The fresh leaves of the putative new species and the morphologically similar allied species, B. subhowii and B. psilophylla, were collected in the field and the nursery, respectively. Total DNA was extracted from nine individuals of the three species (B. parvibracteata, B. subhowii and B. psilophylla) with the CTAB method (
Begonia species and populations included in the phylogenetic analysis (Sectional placement follows
Taxon | Origin | GenBank accession no. | Section | Collector, voucher (Herbarium) |
---|---|---|---|---|
Begonia acetosella Craib. | Mengla, Yunnan, China | MW690106 | Platycentrum | Wang, W.G., WWG005 (HITBC) |
Begonia biflora Ku | Malipo, Yunnan, China | JF975965 | Coelocentrum | Shui, Y.M. et al. 20484 (KUN) |
Begonia chingii Irmsch. | Napo, Guangxi, China | KP710820 | Reichenheimia | Tian, D.K., Li, C. TDK785 (CSH) |
Begonia circumlobata Hance | Xinyi, Guangdong, China | KP710815 | Platycentrum | Tian, D.K., Li, X.P. TDK866 (CSH) |
Begonia cucurbitifolia C. Y. Wu | Yunnan,China | JF975969 | Platycentrum | Y,M,Shui et al.GBOWS1284 (KUN) |
– | JF975968 | – | ||
Begonia edulis Lévl. | Bama, Guangxi, China | KP710813 | Platycentrum | Tian, D.K., Li, C. TDK757 (CSH) |
Begonia grandis Dry. | Yongshun, Huhan, China | KP710828 | Diploclinium | Li, X.P. Li, X.J. LXJ022 (CSH) |
Begonia handelii Irmsch. | Fengshan, Guangxi, China | KP710818 | Platycentrum | Tian, D.K., Li, C. TDK763 (CSH) |
Begonia hatacoa Buch.-Ham. ex D. Don | – | AF485111 | Platycentrum | – |
Begonia hemsleyana Hook. f. | – | KP710806 | Platycentrum | – |
Begonia henryi Hemsl. | Leshan, Sichuan, China | KP710822 | Reichenheimia | Tian, D.K., Tian, L.Z. TDK2249 (CSH) |
Begonia huangii Y. M. Shui & W. H. Chen | Gejiu, Yunnan, China | JF976001 | Coelocentrum | Shui, Y.M. et al. 40782 (KUN) |
Begonia jinyunensis C. I Peng, B. Ding & Q. Wang | Jinyunshan, Chongqing, China | MZ145345 | Platycentrum | – |
Begonia labordei Lévl. | Yunnan, China | KF636452 | Diploclinium | Peng 20520 (HAST) |
Begonia longifolia Blume | Mengla, Yunnan, China | MW690102 | Platycentrum | Wang, W.G., WWG001 (HITBC) |
Begonia longistyla Y. M. Shui & W. H. Chen | Hekou, Yunnan, China | JF976018 | Coelocentrum | Shui, Y.M. et al. 40778 (KUN) |
Begonia megalophyllaria C. Y. Wu | Yunnan, China | JF976026 | Platycentrum | Y,M,Shui et al.D-33(KUN) |
Begonia multangula Blume | Jawa, Lesser Sunda Is. | MN453434 | Platycentrum | – |
Begonia ornithophylla Irmsch. | Guangxi, China | JF976032 | Coelocentrum | Y,M,Shui et al. B2005-061(KUN) |
Begonia parvibracteata X.X.Feng, R.K.Li & Z.X.Liu | Longzhou, Guangxi, China | OL892048 | Platycentrum | Xin Xin Feng, et al. 835307 ( |
OL892049 | ||||
OL892050 | ||||
Begonia pedatifida Lévl. | Tianlin, Guangxi, China | KP710810 | Platycentrum | Tian, D.K., Li, C. TDK774 (CSH) |
Begonia psilophylla Irmsch. | Hekou, Yunnan, China | OL851701 | Platycentrum | – |
OL851702 | – | |||
OL851703 | – | |||
Begonia pulchrifolia D.K.Tian & C.H.Li | Meinvfeng, Leshan, Sichuan, China | KP710811 | Platycentrum | Tian, D.K., et al. TDK2243 (CSH) |
Begonia scorpiuroloba D.K.Tian & Q.Tian | Fanchenggang, Guangxi, China | MZ145351 | Platycentrum | Tian, D.K., et al.TDK2269(CSH) |
Begonia socotrana Hook.f. | Socotra | AF469121 | Peltaugustia | – |
Begonia subhowii S. H. Huang | Malipo, Yunnan, China | OL871361 | Platycentrum | – |
OL871362 | – | |||
OL871363 | – |
We chose 17 species from sect. Platycentrum and 8 species from other sections of Begonia native to mainland China to place the new species in a phylogenetic context (Table
China Guangxi, Longzhou County (龙州县), Zhubu Town (逐卜乡), Bannong Village (板弄屯), Yinghuagu Tourist Resort, 22°33'51"N, 106°57'03"E, (Fig.
Begonia parvibracteata drawn by Yunxiao Liu A хabit B staminate inflorescence C, D front and back views of staminate flower E lateral view of staminate flower F stamen G, H front and back views of pistillate flower with 4 tepals I front view of pistillate flower with 6 tepals J cross section of ovary K styles and stigmas L stigmas M abaxial view of capsule showing wings N lateral view of capsule showing two shorter wings.
Habitat and morphology of Begonia parvibracteata A habitat B flowering plant C creeping rhizome D shoot top with stipule E leaf blade (adaxial) F, G leaf blade (abaxial) H erect stem with inflorescence I, J young inflorescence and bract; K, L front and back views of staminate flower with 4 tepals M lateral view of staminate flower N stamens O, P front and back views of pistillate flower with 4 tepals Q front view of pistillate flower with 6 tepals R cross section of ovary S stigmas T, U immature capsule V dried mature capsule (Photos by Z.X. Liu).
Begonia parvibracteata morphologically resembles B. subhowii and B. psilophylla in rhizome and leaf characters. However, it has narrowly oblique-ovate asymmetric leaf blades, 4 (rarely 6) tepals in pistillate flowers and small (6–8 × 3–5 mm) bracts in inflorescences. These characters differ from the widely ovate leaf blades, 5 (rarely 6) tepals of pistillate flowers, and distinctly large bracts in inflorescences of B. subhowii. B. parvibracteata is dissimilar to B. psilophylla in its 4 (rarely 6) tepals in pistillate flowers and asymmetric, narrowly oblique-ovate leaf blade.
Begonia parvibracteata forms a monophyletic group clustered with B. cucurbitifolia in the phylogenic tree, but the latter has nearly symmetric, 3–4 lobed leaf blade, 5-tepaled pistillate flower, definitely differing from the new species.
Perennial evergreen herb, monoecious, 15–30 cm tall. Rhizome creeping, ca. 8.5–12 cm long and 6–10 mm thick, internode short or not obvious; erect stem only seen at anthesis, ca. 7.5–10 cm long, internodes 1–2 (3), green to reddish-green, glabrous. Stipules brownish-red, translucent, ovate-triangular, ca. 8–10 × 4–5 mm, glabrous. Leaves 3–6 basal and 2–3 aerial, petiole yellowish-green, 18–22 cm long, glabrous; blade asymmetric, ovate to narrowly ovate, 14–16 × 7.5–9 cm; apex acuminate to caudate, base oblique-cordate; leaf margin usually almost entire or occasionally crenate; venation palmate with 6–8 primary veins, adaxially slightly concave, abaxially convex; leaf blade fleshy, abaxially pale-green, glabrous; adaxially green, glabrous. Inflorescences arising from erect stem; dichasial cymes branching one to two times, peduncle 10–12 cm long, glabrous; flowers unisexual, 3–7 flowers per inflorescences; bracts membranous, triangular to widely ovate, brownish-red, 6–8 × 3–5 mm, glabrous. Staminate flower: pedicels pale green, ca. 2–2.3 cm long, glabrous; tepals 4, outer 2 tepals ovate to circular, 13–21 × 12–20 mm, adaxially concave, pinkish-white, abaxially convex, pinkish-white, red hispid; inner 2 obovate, 10–18 × 8–12 mm, margin irregularly entire, white, glabrous; androecium cylindrical, ca. 6.6–7.5 mm across; stamens numerous, ca. 2–2.5 mm long, anthers yellow, clavate, base cuneate, ca. 1.5 mm long. Pistillate flower: pedicels pale green, ca. 2–2.6 cm long, glabrous; tepals 4, occasionally 6, white, irregularly ovate, obovate or cuneate, sub-equal, 18–20 × 10–15 mm, glabrous; ovary yellowish-green, trigonous-ellipsoid, 11–12 × 5–6 mm (wings excluded), glabrous; 2-loculed, placentae axillary, placentae bifid per locule; styles 2, fused at base, yellow, ca. 5–6 mm long, apically Y-shaped, stigma U-shaped, spirally twisted. Capsules nodding, trigonous-ellipsoid, ca. 11–13 × 5–6.5 mm (wings excluded), yellowish-green, glabrous, unequally 3-winged, abaxial wing triangular to ligulate, ca. 10–13 mm long; lateral wings lunate, 3–6 mm long.
Currently known from four localities in Longzhou County and Daxin Countym Guangxi, China. It usually grows on rocks or rock cracks in limestone under forest.
Flowering September-October, fruiting October-December.
The specific epithet “parvibracteata” refers to the short small bracts of the new species. The Chinese name is given as “小苞秋海棠” (Begonia with small inflorescence bracts).
There are three populations with approximately 1000 individuals found in Longzhou County. Another one population with approximately 500 individuals is distributed in the Encheng National Nature Reserve, Daxin County. Some plants of this begonia are over-collected and sold in the local medicinal herb market of Longzhou County. According to the IUCN Red List Categories and Criteria (
The aligned matrix of the ITS sequence data was 727 bp long. The result of Bayesian Inference analysis is shown in Fig.
The nodes with bpp < 0.50 have been collapsed. Sectional placement of taxa is indicated by the following abbreviations: Coe (Coelocentrum), Dip (Diploclinium), Pla (Platycentrum), Rei (Reichenheimia) and Pel (Peltaugustia). The numbers after the species names indicate different populations. The samples of the new species are marked with stars.
The new begonia with 2-loculed ovary, axillary placentation and bifid placentae can be clearly assigned to B. sect. Platycentrum (
Character | B. subhowii | B. psilophylla | B. cucurbitifolia | B. parvibracteata |
---|---|---|---|---|
Leaf blade shape | asymmetric, widely ovate | nearly symmetric, widely ovate to cordate | nearly symmetric, orbicular, 3–4 lobed | asymmetric, narrowly oblique-ovate |
Leaf blade base | asymmetric, oblique-cordate | nearly symmetric, obtuse | nearly symmetric, cordate | asymmetric, oblique-cordate |
Leaf margin | irregularly serrulate | minutely serrulate | minutely serrulate | usually almost entire or occasionally crenate |
Inflorescence bracts | ovate-oblong, 50 × 30 mm, glabrous, apex acuminate | elliptic to ovate-oblong, 7–9 × 4–5 mm, glabrous | subglabrous, caduceus | triangular, 6–8 × 3–5 mm, glabrous |
Tepal number of pistillate flowers | usually 5, rarely 6 | usually 5, rarely 6 | 5 | usually 4, rarely 6 |
Phenology (flowering; fruiting) | April-May; May-July | February-March; March-May | July-August; August-October | September-October; October-December |
Habitat | 700–1500 m alt., limestone, Yunnan; Vietnam | 100–700 m alt., limestone, Yunnan | 430 m alt., limestone, Yunnan | 263 m alt., limestone, Guangxi |
In B. subhowii, there are 5 (occasionally 6) tepals in the pistillate flower and the bracts of inflorescence is distinctly long and large (5 × 3 cm) (Fig.
B. subhowii A–I B. psilophylla J–L B. cucurbitifolia M, N showing similar features comparable to B. parvibracteata A habitat B young leaf blade (adaxial) C leaf blade (abaxial) D inflorescence E bracts F, G front and back views of staminate flower H front view of pistillate flower with 5 tepals I lateral view of pistillate flower J flowering plant K symmetric leaf blade L front view of flower M leaf blade of juvenile plant N mature leaf blade (Photos A–I by R.K. Li J–L by Z.X. Liu M, N by D.K. Tian).
In B. psilophylla, the leaf blade is nearly symmetric, widely ovate with symmetric cordate base, in contrast with the narrower ovate leaf blade and oblique-cordate base of the new species. Furthermore, there are 5 (occasionally 6) tepals in the pistillate flower of B. psilophylla, being different from the 4 (occasionally 6) tepals of B. parvibracteata.
According to the phylogenetic tree, based on ITS sequences, the closest relative of B. parvibracteata is B. cucurbitifolia which is also distributed in south-eastern Yunnan. However, B. cucurbitifolia is remarkably distinct from B. parvibracteata in morphology, including nearly symmetric, 3–4 lobed leaf blade and 5-tepaled pistillate flower.
For the flowering time, B. parvibracteata blooms later compared with its three allied species mentioned above.
This study was supported by the Guangdong Rural Revitalization Strategic Foundation (20211800400042), the Dongguan Municipal Project for Improvement of Social Science and Technology (2020507101165; 2016108101018), the Dongguan Sci-tech Commissioner Program (Grant No. 20221800500042) and the Guangzhou Science and Technology Program (201903010076). We are also grateful to the editor, the reviewers and the English corrector for improving our manuscript.