Draba dongchuanensis Al-Shehbaz, J.P.Yue, T.Deng & H.L.Chen, 2014

Al-Shehbaz, Ihsan A., Yue, Ji-Pei, Deng, Tao & Chen, Hong-Liang, 2014, Draba dongchuanensis (Brassicaceae), a new species from Yunnan, China, Phytotaxa 175 (5), pp. 298-300 : 298-300

Draba dongchuanensis Al-Shehbaz, J.P.Yue, T.Deng & H.L.Chen , sp. nov.

Type:― CHINA. Yunnan: Dongchuan, Shekuai Xiang , 26 ° 09 ′ 21.5 ″ N, 102 ° 55 ′ 40.2 ″ E, 4020 m, 18 Jul 2009, alpine meadow, Ende Liu & Wei Fang 2105 (holotype, KUN ; isotype, KUN ). Figure 1 .

Herbs perennial, cespitose; caudex slender, few branched, covered with petiolar remains of previous years, ultimate branches terminated in rosettes. Stems 8–13 cm tall, erect, simple above, several branched basally, hirsute proximally with a mixture of simple trichomes 0.4–1.0 mm mixed with appressed, subsessile, 2- or 3-rayed, much smaller trichomes, subtomentose distally with appressed, mostly 2-rayed trichomes mixed with fewer simple ones. Basal leaves rosulate, sessile; leaf blade obovate or oblanceolate to narrowly oblong, 5–10 × 2.0– 2.5 mm, hirsute abaxially mainly with simple trichomes 0.7–1.0 mm sometimes mixed with fewer, smaller, stellate, 4-rayed trichomes, subglabrous adaxially, sometime distally with simple trichomes, margin entire, setose-ciliate with simple trichomes 0.8–1.5 mm, apex obtuse; cauline leaves 5–8, sessile, oblong to oblong-lanceolate, middle ones 7–13 mm × 1.5–2.8 mm, pubescent as basal leaves, base minutely auriculate, upper ones narrower, not auriclate at base. Racemes 6–30-flowered, with lowermost one or two flowers bracteate, elongated considerably in fruit; rachis straight, pubescent; middle and lowermost fruiting pedicels 8–12 mm, divaricate, gently curved upwards, pubescent abaxially with subsessile, forked or substellate trichomes mixed with fewer simple ones, glabrous adaxially. Sepals yellow, broadly ovate, 1.8–2.5 mm, ascending, sparsely pubescent abaxially, base of lateral pair slightly saccate, margin membranous; petals yellow, obovate, 3–4 × 1.5–2.0 mm, apex emarginate; claw to 0.5 mm; filaments yellow, subequal, 1.5–2.0 mm, strongly dilated at base; anthers ovate, 0.3–0.4 mm; ovary glabrous; ovules 4–8 per ovary. Fruit lanceolate-linear, 7–10 × 2.0– 2.5 mm, ascending, latiseptate, not twisted; valves glabrous, obscurely veined, base obtuse, apex acute; gynophore 0.2–0.5 mm; style 0.3–0.5 mm. Seeds brown, ovate, 1.5–2.0 × 0.7–1.O mm.

Although reported by its collectors to be common in the alpine meadows where it grows, Draba dongchuanensis is known only from the two sheets of the type collection. It is unique among all of the Himalayan Draba species with yellow flowers by having strongly dilated filament bases. The only exception is D. draboides ( Maximowicz 1880: 424) Al-Shehbaz (2004a: 154) of Gansu and Qinghai provinces, which differs from D. dongchuanensis by having welldeveloped stolons (vs. caudex), crisped (vs. straight) trichomes, usually leafless (vs. leafy stems), and broadly ovate to ovate-oblong (vs. lanceolate-linear fruits).

Only three other Sino-Himalayan species of Draba ( D. amplexicaulis Franchet (1886: 403) , D. polyphylla Schulz (1927: 180) , and D. surculosa Franchet (1886: 401) , have a combination of yellow flowers, basally bracteate racemes, and auriculate cauline leaves. From these, D. dongchuanensis is easily distinguished by having coarsely setose (vs. non-setose) leaves, in addition to the strongly dilated (vs. slender) filament bases.

Draba dongchuanensis resembles D. setosa Royle (1834: 71) , a species of scree and gravelly mountain slopes ( Afghanistan, China (Xizang), India, Pakistan), in having setose-ciliate basal leaves subglabrous adaxially, obovate yellow petals emarginate at apex, and latiseptate fruits similar in size, shape, and style length. However, the novelty differs from D. setosa by its strongly dilated (vs. slender) filament bases, obovate or oblanceolate to narrowly oblong (vs. linear to linear-oblong) basal leaves with obscure (vs. prominent) midvein abaxially, non-scapose (vs. scapose) plants with 5–8 (vs. 0 or rarely 1) cauline leaves, 4–8 (vs. 12–16) ovules per ovary, and slightly narrower fruits 2–2.5 (vs. 2.5–3.5) mm and broader seeds 1.5–2 × 0.7–1 (vs. 1–1.4 × 0.6–0.7) mm.

Plants of Draba dongchuangensis grow in the same general area and can be confused with those of D. mongolica Turczaninow (1842: 256) , especially when have fully mature fruits. However, the latter grows on alpine rocky slopes and crevices (vs. alpine meadows) and is a very widespread species in China (Gansu, Hebei, Heilongjiang, Jilin, Nei Mongol, Qinghai, Shaanxi, Shanxi, Sichuan, Xinjiang), Mongolia, and Russia. The new species can easily be distinguished by its yellow (vs. white) petals, coarsely setose (vs. minutely tomentose) basal leaves, 4–8 (vs. 6–17 cauline leaves, strongly dilated (vs. slender) filament bases, and 4–8 (vs. 12–20) ovules per ovary.

Figures

FIGURE 1. Draba dongchuanensis. A, Plant. B, Sepal. C, Petal. D, Stamen. E, Fruit and fruiting pedicel. Scale bars: A = 1 cm; B–E = 1 mm. Drawn from the holotype by Al-Shehbaz.