Rorippa hengduanshanensis Q.J. Zheng, C.C. Yu, T.S. Han & Y.W. Xing, 2021

Zheng, Quan-Jing, Yu, Chih-Chieh, Xing, Yao-Wu & Han, Ting-Shen, 2021, A new Rorippa species (Brassicaceae), R. hengduanshanensis, from the Hengduan Mountains in China, Phytotaxa 480 (3), pp. 210-222 : 219-220

Rorippa hengduanshanensis Q.J. Zheng, C.C. Yu, T.S. Han & Y.W. Xing , sp. nov.

Type:— CHINA. Yunnan: Changyi Country , Liantie Town , Eryuan County, 25°53’04.19”N, 99°51’43.88”E, 1754m, 14 August 2020, Quan-Jing Zheng 4639 (holotype: HITBC 0035715 !, Isotype: HITBC, PE, KUN) .

Herbs annual, 20–50 cm tall, glabrous or rarely sparsely pubescent. Stems often branched basally and apically. Basal leaves withered by flowering. Lower and middle cauline leaves auriculate or not; petiole absent or 1–5 cm; leaf blade lyrate-pinnatipartite or undivided, obovate, oblong, or lanceolate, (2.5–)5–12(–16) × (1–)1.5–3.5(–5) cm, margin entire, irregularly crenate, or serrate, apex obtuse or subacute; terminal lobe oblong, elliptic, or oblong-lanceolate, to 7 × 4 cm; lateral lobes absent or 1–3(or 4) on each side of the midvein. Uppermost leaves usually sessile, auriculate or not; leaf blade lanceolate or oblong, margin entire, denticulate, or serrulate, apex acute or acuminate. Racemes ebracteate or rarely lowermost 1 or 2 flowers bracteate. Fruiting pedicels slender, ascending, divaricate, or rarely slightly reflexed, straight, (3–)5–10(–12) mm. Sepals often green or pinkish, ascending, oblong-ovate, 2–3 × 0.8–1.5 mm, margin membranous. Petals yellow, obovate, or spatulate, (1.5–)2–3(–3.5) × 1–2 mm, rarely absent. Filaments 2– 3 mm; anthers oblong, 0.5–0.8 mm. Ovules (60–)70–110 per ovary. Fruit linear, (1.5–)2–3(–3.5) cm, usually flattened silique, often curved upward; valves thin papery, not veined; style (0.5–)1–1.5(–2) mm, slender, narrower than fruit. Seeds reddish brown, ovate or ovate-orbicular, 0.8–1 × 0.5–0.8 mm, foveolate, uniseriate or nearly so. Fl. & Fr. Jun–Oct. 2 n = 48.

Distinguishing features: — Rorippa hengduanshanensis differs from R. benghalensis in the ebracteate racemes; from R. dubia in the flattened silique, the presence of four petals and the ploidy level (2 n =6 x =48); and from R. indica in the uniseriate seeds.

Phenology: — Rorippa hengduanshanensis flowers in June and July, and fruits between August and October.

Distribution & habitat: — Rorippa hengduanshanensis is endemic in Yunnan, and Sichuan provinces of China, where it grows at roadsides, field margins, gardens, and riverbanks at altitudes of 1500 to 3000 m.

Etymology: —This species is named to reflect its geographic distribution, the Hengduan Mountains, where “shan” is the Mandarin pronunciation of “mountain”.

Chinese name:—ḄṂ山Ṛṿ

Proposed IUCN conservation status:— Nearly Threatened. Rorippa hengduanshanensis is distributed in the southern HDM, especially common in Dali Bai Autonomous Prefecture. It is abundant in wet places or roadsides, establishing large populations locally. However, because it appears to only distribute in high-altitude regions, which is potentially threatened by global climate change, we propose a provisional IUCN category of NT for the species (IUCN 2012).

Notes: The main herbaria in Yunnan and Sichuan (e.g., KUN, CDBI) have many specimens of R. indica collected from the high-altitude regions of the southern HDM. However, only a few of them were available for fruit observation dissection. Hence, there is an operational difficulty in confirming the assembly of these specimens to R. hengduanshanensis . All the specimens examined in this study were collected by the authors during field works in 2017–2020.

Additional specimen examined:— CHINA, Yunnan: Zhongyang Country, Yangcen Town , Jianchuan County, 2257 m, 26°27’51.18”N, 99°50’22.37”E, 15 August 2020, yxing 4640 ( HITBC, PE, KUN); Yangjia Country, Yangcen Town , Jianchuan County , 2673 m, 26°33’21.48”N, 99°44’46.44”E, 15 August 2020, yxing 4641 ( HITBC, PE, KUN) .