Seven new species of Begonia (Begoniaceae) in Northern Vietnam and Southern China

Seven new species were found.

The Tonkin region is one of the biodiversity hotspots worldwide that include Northern Vietnam and Southern China. This region is characterized by the massive area of the limestone landform and the lowland less than 1200 m elevation. The floristic region mainly covers the northernmost region from the North-west to North-east in Vietnam that borders with the South-western Guangxi and South-eastern Yunnan in China. In the last ten years, a large number of new species in different families have been discovered in the region, such as Begoniaceae, Gesneriaceae, Magnoliaceae etc.

Since 2016, KIB (Kunming Institute of Botany) and CPC (Centre for Plant Conservation of Vietnam) have conducted several surveys in the transboundary karst regions in Northern Vietnam and Southern China and seven new species in the genus Begonia Linn. (Begoniaceae) are firstly described. Amongst them, two species, Begonia albopunctata Y.M. Shui, W.H. Chen & H.Q. Nguyen and B. erectocarpa H.Q. Nguyen, Y.M. Shui & W.H. Chen, respectively belong to section Sphenanthera with berry fruits and sec­tion Leprosae with clavate berry fruits; four species, B. gulongshanensis Y.M. Shui & W. H. Chen, B. minis­sima H.Q. Nguyen, Y.M. Shui & W.H. Chen, B. mollissima Y.M. Shui, H.Q. Nguyen & W.H. Chen, B. rhytidophylla Y.M. Shui & W.H. Chen, belong to section Coelocentrum with parietal placentation; one species, Begonia bambusetorum H.Q. Nguyen, Y.M. Shui & W.H. Chen, belongs to section Diploclinium with 3-loculed ovary and capsules. The diagnostic characters of these species are described and illustrated in the text and photographs.

1. Begonia albopunctata Y.M.Shui, W.H.Chen & H.Q.Nguyen, sp. nov.

The new species is similar to B. hahiepiana H.Q. Nguyen & Tebbitt in broadly ovate asymmetric leaves with slightly truncate or round apex and the corned berry fruit, but different from it in the broadly ovate or rotund leaves (vs. ovate), al­most flat adaxial surface of leaves (vs. puckered), glabrous outer surface of petals (vs. with red trichomes), 4-loculed and glabrous berry fruit covered by dense white spots (vs. 3-loculed and pubescent fruit covered by the lax white spots). The species only grows in deep ground amongst rocks in limestone forests.

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Begonia albopunctata

2. Begonia bambusetorum H.Q.Nguyen, Y.M.Shui & W.H.Chen, sp. nov.

The new species is similar to Begonia sinovietnamica C. Y. Wu in their habit and distribution, but different from the latter species in expanding vil­lous hairs on petiole and peduncles (vs. pubescent), 2 petals of the male flowers (vs. 4 petals), 2 petals of the female flowers (vs. 5 rarely 4 petals). The epithet refers to the habitat of the new species: the bamboo forests along streams.

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Begonia bambusetorum

3. Begonia erectocarpa H.Q.Nguyen, Y.M.Shui & W.H.Chen, sp. nov.

The new species is similar to Begonia longicarpa K.Y. Guan et D. K. Tian in the clavate berry fruit, but differs from it in its hispid petiole (vs. pubescent), five female petals (vs. three) and short segments of placentation per locule (vs. long segments). The species just grows on soil within the secondary tropical evergreen lowland rainforest and broad-leaved forests on the slopes and ridge of crystalline lime­stone with highly eroded earth at an elevation 400–700 m above sea level.

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Begonia erectocarpa 

4. Begonia gulongshanensis Y.M.Shui & W.H.Chen, sp. nov.

The new species is similar to Begonia daxinensis T. C. Ku, but different from it in its ovate leaves (vs. broadly ovate in B. daxinensis), slightly oblique leaf base (vs. ex­tremely oblique), glandulose-villous on peduncles, pedicels, adaxial surface of exterior tepals and fruits (vs. glabrous, sparely eglandulose-pubescent), filaments connected to a half (vs. only at base), the smaller petals of male flowers, the smaller petals of the female flowers. The species only grows on the moist surface of shady cliffs at the entrance to shallow caves in a deep valley.

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Begonia gulongshanensis

5. Begonia minissima H.Q.Nguyen, Y.M.Shui & W.H.Chen, sp. nov.

The new species is similar to Begonia rugosula Aver. in the small leaves and climbing habit, but different from it in the round leaf top (vs. acute leaf top), flat surface on the adaxial surface of the leaves (vs. uneven surface in B. rugosula), ovate interior petals (vs. narrowly obovate or narrowly obovate), 2-branching stigma (vs. slightly spherical). The species just grows in limestone crevices of cliffs.

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Begonia minissima

6. Begonia mollissima Y.M.Shui, H.Q.Nguyen & W.H.Chen, sp. nov.

The new species is similar to Begonia guangxiensis T.C. Ku in the dense white villous hairs on the whole plants, differs from the latter in the shorter hairs of plants, its one obtuse leaf lobe, subequal three wings of the fruit (vs. unequal three wings), narrowly semi-lunar major wings (vs. broadly square major wings). The species only grows on cliffs in limestone forests.

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Begonia mollissima

7. Begonia rhytidophylla Y.M.Shui & W.H.Chen, sp. nov.

The new species is similar to Begonia crystinilla Y.M. Shui & W. H. Chen in the thick texture and shape of leaves, but differs in the flat adaxial surface of leaves with sparse setae (vs. the uneven with dense setae), pubescent abaxial surface of leaves (vs. lane), triangulate major wing of fruit (vs. semi-lunar). The species only grows on rocks at the entrance to caves or on the shady slope in limestone forests.

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Begonia rhytidophylla

This research is supported by the National Natural Science Foundation of China (grant nos. 31370228, 31770251, 31070174 and 30270109), Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences(Y4ZK111B01), and published as "Seven new species of Begonia (Begoniaceae) in Northern Vietnam and Southern China" on PhytoKeys.