Eutrema racemosum Al-Shehbaz, G.Q. Hao & J.Q. Liu, sp. nov.

Type:— China. Sichuan: Yajiang Xian, near glaciers, shrub margin of stream, 3200‒4000m, 22 August 2013, Liu, jianquan & Hao, Guoqian 14048 (Holotype, SZ). Fig. 1.

Herbs, perennial, glabrous throughout or rarely puberulent, with a caudex and slightly fleshy root. Stems 5‒20 cm tall, erect or rarely ascending to decumbent, simple, often few from caudx. Basal leaves rosulate, somewhat fleshy; petiole 1‒5cm; leaf blade ovate, suborbicular, or lanceolate, 7‒11 × 4‒8 mm, pinnately veined, base rounded, truncate, to cuneate, margin entire, apex obtuse to subacute; lowermost cauline leaves petiolate, upper ones sessile, lanceolate or linear-lanceolate, 8‒15 × 2‒5 mm, base cuneate, margin entire, apex subacute. Racemes elongated in fruit, 3‒ 15(‒30) mm; fruiting pedicels slightly reflexed, 4‒8 mm. Sepals ovate, 1.5‒2 mm, persistent through fruit maturity; petals white, spathulate or broadly obovate, 2‒3 × 1.5‒2 mm, base cuneate, apex rounded; stamens6, subequal; ovules 4‒10 per ovary. Fruit linear, lanceolate, to narrowly oblong, 4‒8 × 0.8‒1.2 mm, valves cuneate at both ends, with a prominent midvein; septum mostly perforate; style obsolete to 0.6 mm. Seeds oblong, plump, ca. 2 × 1.5 mm, brownblack. Flowering: May‒July. Fruiting: July‒September.

Additional specimens examined: CHINA. Sichuan: Jiulong Xian, Jichou Shan pass, J. Q. Liu & G. Q. Hao 14046 (SZ); Dege xian, Que’er Shan, J. Q. Liu & G. Q. Hao 14090 (SZ); SE of Shiqu Xian, J. Q. Liu & G. Q. Hao14098 (SZ); Kangding Xian, Dapao Shan, 4300 m, Harry Smith 11260 (PE, UPS). Hebei: Wei Xian, Xiaowutai Shan, Xiaowutai Expedition 74155 (PE).

Eutrema racemosum is most similar to E. heterophyllum, and their geographical ranges overlap in western Sichuan. However, it differs from the latter by having elongated (vs. compact) fruiting racemes. It is also similar to the allopatric E. edwardsii which also has elongated racemes but fruiting pedicels in E. edwardsii are often divaricate-ascending and curved upward, rather than somewhat reflexed as in Eutrema racemosum.

In two populations where Eutrema racemosum and E. heterphyllum were sympatric, a few individuals with intermediate morphology were discovered (Fig. 3: C). These individuals were confirmed as interspecific hybrids by the molecular evidence presented below.