Breynia hiemalis Huan C. Wang & Feng Yang, 2022

Yang, Feng, Chen, Chao, Ye, Jing-Yi, Wu, Jian-Yong & Wang, Huan-Chong, 2022, Breynia hiemalis (Phyllanthaceae, Phyllantheae), a new species from Yunnan, south-west China, PhytoKeys 206, pp. 75-86 : 75

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

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!) .

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.

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.

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.

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. Breynia 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. Breynia 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).

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.

Figures

Figure 1. Breynia hiemalis. (Drawn by Jing-Yi Ye from type specimen H. C. Wang et al. YJ 16225) A habit B pistillate flower (apical view) C fruit D staminate flower (apical view) E staminate flower (lateral view).

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.

Figure 3. Holotype of Breynia hiemalis (YUKU- 02074690).

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.

Figure 6. Breynia hiemalis (A, D), B. compressa (B, E), B. granulosa (C), B. delavayi (F). A-C pistillate flowers D-F staminate flowers.