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Research Article
Breynia hiemalis (Phyllanthaceae, Phyllantheae), a new species from Yunnan, south-west China
expand article infoFeng Yang‡, Chao Chen§, Jing-Yi Ye‡, Jian-Yong Wu|, Huan-Chong Wang‡
‡ Yunnan University, Kunming, China
§ Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Yuanjiang, China
| Yuxi Forestry and Grassland Bureau, Yuxi, China
¶ Herbarium of Yunnan University, Kunming, China

Corresponding author: Huan-Chong Wang ( hchwang@ynu.edu.cn )

Academic editor: Peter Bruyns
© 2022 Feng Yang, Chao Chen, Jing-Yi Ye, Jian-Yong Wu, Huan-Chong Wang.
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: Yang F, Chen C, Ye J-Y, Wu J-Y, Wang H-C (2022) Breynia hiemalis (Phyllanthaceae, Phyllantheae), a new species from Yunnan, south-west China. PhytoKeys 206: 75-86. https://doi.org/10.3897/phytokeys.206.85241
Open Access

Abstract

Breynia hiemalis Huan C. Wang & Feng Yang (Phyllanthaceae), of sect. Cryptogynium (Müll.Arg.) Welzen & Pruesapan in subg. Breynia, is described from Yunnan, south-west China. It is known from only a single locality in the valley of the Yuanjiang River, and usually occurs in the understory of the savanna vegetation. It is characterized by its broadly elliptic to orbicular leaf blades, shallowly plate-like calyces of the staminate flowers, ovaries with clearly erose rim and urceolate capsules. Morphological comparisons with similar species are also presented.

Keywords

Breynia sect. Cryptogynium, endemism, Sauropus, savanna, Yuanjiang River

Introduction

The family Phyllanthaceae, a segregate from Euphorbiaceae sensu lato, is a pantropical group of herbs, shrubs and treelets (Kathriarachchi et al. 2005; Hoffmann et al. 2006). It currently consists of about 2000 species, with more than 1200 placed in the largest tribe Phyllantheae (Govaerts et al. 2000; Hoffmann et al. 2006). Within the Phyllantheae, the generic classification is still contentious (Hoffmann et al. 2006; Wagner and Lorence 2011; Pruesapan et al. 2012; Van Welzen et al. 2014; Jangid and Gupta 2016; Bouman et al. 2022). Recent molecular studies clearly demonstrated that Phyllanthus L. (in the traditional sense), the largest genus of Phyllanthaceae, with more than 800 species, is paraphyletic since Glochidion J. R. Forst. & G. Forst., Breynia J. R. Forst. & G. Forst. and Synostemon F. Muell. are nested within it (Bouman et al. 2021, 2022). Some authors suggested placing most species of the Phyllantheae in Phyllanthus. This would make Phyllanthus a large and morphologically heterogeneous group with more than 1200 species (e.g. Hoffmann et al. 2006; Wagner and Lorence 2011; Ralimanana et al. 2013; Kato and Kawakita 2017; Falcón-Hidalgo et al. 2020). Conversely, other authors (for example, Pruesapan et al. 2008; Pruesapan 2010; Van Welzen and Pruesapan 2010; Pruesapan et al. 2012; Bouman et al. 2018, 2021) prefer to divide Phyllanthus s. l. into several smaller, monophyletic genera that can be characterized morphologically. More recently, Bouman et al. (2022) split Phyllanthus s. l. into thirteen monophyletic and morphologically recognizable genera, where Breynia was kept as a separate genus.

Breynia and Sauropus Blume in the strict sense are closely related; both share bifid or emarginate styles, non-apiculate anthers, smooth seeds, and they generally possess sepal scales (Van Welzen et al. 2014). From the results of a well-sampled phylogenetic analysis, Van Welzen et al. (2014) expanded Breynia to include the south-east Asian species of Sauropus and reinstated the Australian genus Synostemon, previously relegated to a section of Sauropus, making each genus monophyletic and morphologically definable. The newly circumscribed Breynia is a moderately-sized genus of 85 to 90 species (Van Welzen et al. 2014; Bouman et al. 2022). It contains three infrageneric groups, including subg. Breynia and subg. Sauropus (Blume) Welzen & Pruesapan, with subg. Breynia subdivided into sect. Breynia and sect. Cryptogynium (Müll. Arg.) Welzen & Pruesapan. Members of Breynia are distributed mainly from Australia to tropical and subtropical Asia, with a center of diversity in south-east Asia (Van Welzen 2003; Bouman et al. 2022; POWO 2022). Twenty species of Breynia are found in China, including 15 species formerly placed in Sauropus, and most species occur in the southern and south-western regions (Li 1994; Li and Esser 2008; Li and Gilbert 2008). Recently, a new species of Breynia was described from Yunnan, south-west China by Yang et al. (2022). This brings the total number of Chinese species to 21, of which five species belong to sect. Cryptogynium, seven species belong to sect. Breynia, and nine species belong to subg. Sauropus.

During fieldwork in Yuanjiang National Natural Reserve, Yunnan Province (SW China), in December 2015 and January 2022, we came across a dwarf plant with discoid staminate flowers and 3 stigmas spreading horizontally from the top of obconical ovary, obviously belonging to Breynia according to the generic delimitation of Van Welzen et al. (2014) and Bouman et al. (2022). This could not be assigned to any previously known species from China (Li and Gilbert 2008), or from any of the adjacent south-east Asian countries, i.e. Vietnam, Laos, Thailand and Myanmar (Beille 1927; Pham 2003; Van Welzen 2003; Chakrabarty and Balakrishnan 2018; Van Welzen 2022; Van Welzen and Chayamarit 2022). Comparison with morphologically similar species supports recognizing this plant as an undescribed species.

Materials and methods

The new species was studied both in the field and in the herbarium. The collections of similar species housed at KUN, PE, XTBG, YUKU, and digital images available at the JSTOR Global Plants (https://plants.jstor.org/), the Chinese Virtual Herbarium (http://www.cvh.ac.cn/), and the Global Biodiversity Information Facility (https://www.gbif.org/) were reviewed. Surveys of pertinent taxonomic literature (for example, Beille 1927; Li 1994; Pham 2003; Van Welzen 2003; Ma et al. 2006; Li and Gilbert 2008; Van Welzen et al. 2014; Chakrabarty and Balakrishnan 2018; Van Welzen 2022; Van Welzen and Chayamarit 2022) were carried out. Measurements were made under a stereomicroscope (Olympus SZX2, Tokyo, Japan) using a ruler and a metric vernier caliper.

Taxonomy

Breynia hiemalis Huan C. Wang & Feng Yang, sp. nov.

urn:lsid:ipni.org:names:77303992-1
Figs 1, 2, 3

Type

China. Yunnan Province: Yuanjiang County, Pupiao, 600–700 m, 23°28'37"N, 102°10'37"E, in savanna on a mountain slope, 12 Jan. 2022, H. C. Wang et al. YJ16225 (holotype YUKU-02074690!; isotypes YUKU!, PE!, HITBC!).

Figure 1. 

Breynia hiemalis. (Drawn by Jing-Yi Ye from type specimen H. C. Wang et al. YJ16225) A habit B pistillate flower (apical view) C fruit D staminate flower (apical view) E staminate flower (lateral view).

Diagnosis

Breynia hiemalis can easily be distinguished from all morphologically similar species by plants glabrous throughout, by its broadly elliptic to orbicular and relatively small (4–21 × 4–17 mm) leaves, calyx of staminate flower shallowly plate-like, ovary rim conspicuously erose, and the urceolate capsule with a raised and lobed apical rim.

Figure 2. 

Breynia hiemalis A habit B phyllanthoid branch showing pistillate flower and staminate flowers C stipule D staminate flower (apical view) E pistillate flower (apical view) F calyx in fruit (dorsal view) G fruit. Photographed by H. C. Wang from type locality in January 2022.

Description

Dwarf shrubs or subshrubs, 10–20 (–30) cm tall, monoecious, glabrous throughout, with phyllanthoid branching. Main stems more or less procumbent to ascending, brown, with 4 shallow ribs, sometimes rooting at the lower nodes; branches green, deciduous, ascending, 3‒8 cm long. Cataphylls lanceolate, to 1 mm long, arranged spirally at the base of the plagiotropic branchlets. Leaves on ultimate branchlets distichous, simple; stipules triangular-lanceolate, usually auriculate basally, 1.5–2.0 mm long; petiole 1.2–1.6 × 0.3–0.5 mm; blade broadly elliptic to orbicular, rarely slightly ovate, papery, 4–21 × 4–17 mm, length/width ratio 1–1.5, base rounded to broadly cuneate, margin entire, flat, apex usually rounded, sometimes truncate, retuse, rarely mucronate, adaxially green, abaxially grey or slightly glaucous; venation pinnate, lateral veins 4 or 5 pairs, reticulate veins obscure. Inflorescences axillary, peduncles very short, ± 0.1 × 0.1 mm, with minute bracts, male or female flowers usually solitary, staminate flowers proximal, pistillate flowers usually distal. Staminate flowers: pedicel slender, ± 7 mm long; calyx shallowly plate-like, ± 4 mm in diam., red, 6-lobed; lobes biseriate, broadly obovate, slightly fleshy, 0.9–1.2 × 1.1–1.3 mm, apex obtuse or retuse, scales present; stamens 3, filaments connate, androphore ± 0.2 mm long, splitting horizontally, branches up to 0.5 mm long with anthers underneath, anthers ± 0.3 × 0.3 mm. Pistillate flowers: pedicel ± 3 mm long, thickening upwards; calyx ± 6 mm in diam., greenish, whitish yellow, or pinkish, lobes biseriate, obovate, subcoriaceous, outer lobes 2.5–3.0 × ± 2.5 mm, slightly longer and wider than the inner, inner lobes ± 2.5 × 2.1–2.5 mm, apex obtuse to truncate, shortly and abruptly acuminate; ovary obconical, 1.2–1.6 mm in diam., 3-locular, 2 ovules per locule, rim present at the apex, obviously erose; stigmas 3, spreading horizontally from top of ovary, apex split and recurved through ± 180°, sepals persistent and enlarged to ± 5 × 4 mm in fruit. Capsules urceolate, ± 4 × 5–6 mm, with a raised, lobed apical rim and persistent stigmas.

Figure 3. 

Holotype of Breynia hiemalis (YUKU-02074690).

Phenology

Flowering from December to January, fruiting from January to February.

Etymology

The epithet ‘‘hiemalis’’ is Latin for ‘‘belonging to winter’’, referring to the flowering period of this new species.

Distribution and habitat

Breynia hiemalis appears to be rare and is endemic to Yunnan, south-west China. It is known from only a single locality in the valley of the Yuanjiang River, which flows from Yunnan (south-west China) through northern Vietnam to the Gulf of Tonkin (Fig. 4). The climate in Yuanjiang valley is characterized by a long dry season (the dry season can be further divided into a cool dry season (November to February) and a hot dry season (March to April)), with an annual average temperature of 24 °C and a mean annual evaporation capacity of 2700–3800 mm, that is three to six times higher than the mean annual precipitation (600–800 mm), and with 80–90% of the precipitation concentrated in the wet season (from May to October) (Jin 2002; Shen et al. 2010; Zhou et al. 2017). Breynia hiemalis grows in savanna on a mountain slope (Fig. 5) at elevations of 500–700 m, together with Lannea coromandelica (Houtt.) Merr. (Anacardiaceae), Adina cordifolia (Roxb.) Brandis (Rubiaceae), Bauhinia brachycarpa Wall. ex Benth. (Fabaceae), Tephrosia purpurea (L.) Pers. (Fabaceae), Woodfordia fruticosa (L.) Kurz (Lythraceae), Waltheria indica L. (Malvaceae), Jasminium mesnyi Hance (Oleaceae), Searsia paniculata (Wall. ex G. Don) Moffett (Anacardiaceae), Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult. (Poaceae), and others.

Figure 4. 

South-western China, showing the known distribution (red star) of Breynia hiemalis. The blue lines represent the rivers.

Figure 5. 

Habitat of Breynia hiemalis A distant view of the type locality B nearby view.

Additional specimens examined

(Paratypes). China. Yunnan: Yuanjiang County, Pupiao, 17 Dec. 2015, H. C. Wang et al. YJ736 (YUKU).

Taxonomic notes

According to Van Welzen et al. (2014) and Bouman et al. (2022), B. hiemalis should be assigned to sect. Cryptogynium because of its horizontal anthers (the androphore splits apically into three horizontal arms with the anthers hanging underneath) and ovary with a rim. Prior to the present study, only five species of sect. Cryptogynium were recorded in China, namely B. compressa (Müll. Arg.) Chakrab. & N. P. Balakr. (a member of the B. quadrangularis (Willd.) Chakrab. & N. P. Balakr. complex which was recognized as a distinct species by Chakrabarty and Balakrishnan (2015)), B. delavayi (Croizat) Welzen et Pruesapan, B. pierrei (Beille) Welzen et Pruesapan, B. similis (Craib) Welzen et Pruesapan and B. tsiangii (P. T. Li) Welzen et Pruesapan (Li and Gilbert 2008; Van Welzen et al. 2014; Chakrabarty and Balakrishnan 2015). Breynia hiemalis shows some resemblance to B. compressa and B. delavayi in its dwarf habit and axillary inflorescences. However, B. hiemalis can be distinguished from B. compressa by several characters, namely stems more or less procumbent to ascending (vs. erect or arching in B. compressa), calyx of the staminate flower shallowly plate-like (vs. star-shaped), lobes broadly obovate (vs. suborbicular or squarish), apex obtuse or retuse (vs. emarginate-truncate to deeply bilobulate) (Fig. 6: D, E), ovary rim erose (vs. retuse) (Fig. 6: A, B), capsule urceolate (vs. ovoid), with raised and lobed apical rim (vs. with low and smooth apical rim). Additionally, B. hiemalis flowers in winter (from December to January), whereas B. compressa flowers from summer to autumn (from April to October). Breynia hiemalis differs strikingly from B. delavayi in its obscure reticulate veins (vs. reticulate veins elevated on both surfaces) and calyx of the staminate flower shallowly plate-like (vs. star-shaped) (Fig. 6: D, F).

Figure 6. 

Breynia hiemalis (A, D), B. compressa (B, E), B. granulosa (C), B. delavayi (F). A–C pistillate flowers D–F staminate flowers.

Of the species of Breynia found in south-east Asia, B. hiemalis is also morphologically similar to B. granulosa (Airy Shaw) Welzen & Pruesapan, from eastern Thailand. Nevertheless, B. granulosa differs from B. hiemalis in having obovate leaves (vs. broadly elliptic to orbicular, rarely slightly ovate in B. hiemalis), calyx of staminate flower campanulate (vs. shallowly plate-like), androphores ± 0.8 mm (vs. ± 0.2 mm) long, smaller pistillate flowers, usually 4–5 mm (vs. ± 6 mm) in diam., stigmas ascending (vs. horizontally spreading) (Fig. 6: A, C) and ovoid (vs. urceolate) capsules. Breynia hiemalis is also similar to B. poilanei (Beille) Welzen et Pruesapan from Vietnam, but it clearly differs from the latter by its more or less procumbent to ascending stems (vs. erect in B. poilanei), 0.1–0.2 (–0.3) m (vs. 1.5 m) tall, branches 3–8 cm (vs. 5–15 cm) long, stipules triangular-lanceolate (vs. triangular), 1.5–2.0 mm (vs. 0.5 mm) long, leaves broadly elliptic to orbicular, rarely slightly ovate (vs. ovate, rarely orbicular), capsules 4 mm (vs. up to 10 mm) wide. A key to distinguish the members of Breynia sect. Cryptogynium in China is given below.

Key to Chinese species of Breynia sect. Cryptogynium

1 Shrubs 1–3 m tall 2
– Dwarf shrubs or subshrubs 0.1–1.0 m tall 4
2 Leaves ovate, 0.7–3.7 × 0.5–1.9 cm Breynia similis
– Leaves ovate to lanceolate, 6–10 × 3–4 cm 3
3 Leaves usually ovate, rarely ovate-lanceolate, papery, base rounded, apex caudate-acuminate B. tsiangii
– Leaves ovate-lanceolate to lanceolate, coriaceous, base cuneate, apex acuminate B. pierrei
4 Calyx of staminate flower shallowly plate-like B. hiemalis
– Calyx of staminate flower star-shaped 5
5 Branches pubescent, leaves orbicular, base shallowly cordate, truncate or rounded, lateral veins robust, reticulate nerves prominent B. delavayi
– Branches glabrous; leaves ovate, elliptic or nearly rounded, base rounded or broadly cuneate, lateral veins slender, reticulate nerves obscure B. compressa

Acknowledgements

We thank the curators of the Yuanjiang Savanna Ecosystem Research Station who helped us with collecting. We express our gratitude to Pingping Li for the distribution map of the new species. We are grateful to Dr. Libing Zhang (Missouri Botanical Garden) for critically reading the manuscript and improving the English, and we give special thanks to two anonymous reviewers and the editor for their valuable comments and suggestions. This research was supported by the National Natural Science Foundation of China (grant no: 31960040) and the Second Tibetan Plateau Scientific Expedition and Research (STEP) programme (2019QZKK0502).

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