Desmodium uncinatum (Jacq.) De Candolle (1825: 331)

Jiang, Kai-Wen, Tian, Bin & Pan, Bo, 2022, Legume additions to the flora of China, Phytotaxa 532 (1), pp. 1-21 : 2

. Desmodium uncinatum (Jacq.) De Candolle (1825: 331) .

Hedysarum uncinatum Jacquin (1798: 27) . Meibomia uncinata (Jacq.) Kuntze (1891: 197) .

Type:— VENEZUELA. “crescit Caracas” (lectotype W, isolectotypes W). Fig. 1.

Description: —Subshrubs, prostrate to ± scandent, branched. Stem slender, striate, densely covered with hooked hairs ca. 1 mm. Stipules brown, ca. 5 mm, longitudinally striate, ciliate at margin, caducous; leaves trifoliolate; petioles 2–5.5 cm, cylindrical, grooved above, densely hairy as stem; rachis 0.5–1.5 cm; leaflets lanceolate, apex acute, mucronate, base broadly cuneate to rounded, adaxial surface deep green, with a silvery plaque along the midvein, sparsely covered with appressed hairs, abaxial surface light green, hairy as the adaxial surface but much denser, terminal leaflet 3.5–9 × 1.3–4 cm, lateral ones slightly shorter, oblique; stipels 2–4 mm, linear-lanceolate, ciliate at margin; petiolules 1–3 mm, more densely hairy than stem. Inflorescence a pseudoraceme, axillary or terminal, with terminal ones (20–26 cm) much longer than axillary ones (7–12 cm), with a long peduncle, both peduncle and rachis hairy as stem; with two flowers per node; bracts ovate, ca. 5 mm, acute at apex, sparsely pubescent outside, marked with stripes as stipules, caducous. Pedicels 3–9 mm, hairy as peduncle. Calyx bilabiate, ca. 3 mm, with tube campanulate, sparsely covered with spreading hairs. Corolla pink, all petals short clawed; standard ca. 10 mm, obovate, retuse at apex, with two light green nectar guides at base; wing petals ca. 8 mm, narrowly obovate to oblong, obtuse at apex; keel petals ca. 5 mm, falcate to narrowly obovate, obtuse at apex. Stamens monadelphous, ca. 10 mm, vexillary stamen partially fused with the staminal tube. Loments ca. 4 cm, densely covered with white hairs, mature fruits and seeds not seen.

Distribution and habitat: — Desmodium uncinatum is native to North, Central and South America, but it has been widely introduced to Australia and Southeast Asia ( Ohashi 1973, Lima et al. 2014). It was introduced and cultivated as a tropical pasture in Guangdong, Guangxi, Hainan, Taiwan, and Yunnan in China multiple times ( Huang et al. 1991) but was never formally recorded as a naturalized species in Chinese floras ( Huang & Ohashi 1993, 2010, Yang & Huang 1995). This species has successfully naturalized in Yunnan Province. It grows on roadside slopes at an elevation of 1376 m.

Phenology: —Flowering from October to December; fruiting in December.

Chinese name: —The Chinese name of Desmodium uncinatum is ffi叶山ặḑ, in which “ ffi叶 ” means “silver leaves”, which refers to the silvery plaque along the midvein on the adaxial surface of leaflets; “ 山ặḑ ” is the Chinese common name for Desmodium Desvaux (1813: 122) s. str. (see http://duocet.ibiodiversity.net/).

Specimens examined:— CHINA. Guangdong: Guangzhou, Genetic Laboratory test field of South China Botanical Garden, “introduced from Australia”, 15 th Dec. 1980, S. Q. Chen 18686 (IBSC). Guangzhou, South China Botanical Garden, 23 rd Dec. 1981, F. W. Xing, B. H. Chen & C. X. Huang 111 (IBSC). Taiwan: Nantou Hsien, Jenai Hsiang, Meifeng-Tsuefeng, on roadside, alt. 2200 m, C. M. Wang, H. M. Lin & C. P. Lu 3265 (IBSC). Yunnan: Lincang, Yongde, Yongkang, Kui-Ge Mountains E, along the S 313, on slopes of the roadside, alt. 1376 m, 18 th Oct. 2020, P. Li, Z. H. Liu, S. Y. Wang & H. L. Zheng 008662 (HZU, NPH).

Discussion: — Yang & Huang (1995) recognized 27 species and 5 varieties of the genus Desmodium distributed in China, including D. caudatum De Candolle (1825a: 337) , which was transferred to the new genus Ohwia H. Ohashi (1999: 243) . This treatment was recognized by Huang & Ohashi (2010a, 2010b), and thus Huang & Ohashi (2010b) recognized 32 species of Desmodium distributed in China. However, the genus Desmodium s. lat. is not monophyletic and needs to be divided ( Jabbour et al. 2018). In recent years, a series of work focusing on the division of Desmodium s. lat. had been done ( Ohashi & Ohashi 2012, 2018a, 2018b, 2020, Ohashi et al. 2018a, 2018b, 2019a, 2019b, 2020a, 2020b). As for Chinese taxa, all native taxa recognized by Yang & Huang (1995) and Huang & Ohashi (2010b) should be transferred to Grona Loureiro (1790: 459) , Huangtcia H. Ohashi & K. Ohashi (in Ohashi et al. 2018a: 182), Leptodesmia ( Bentham 1852: 221) Bentham & Hooker f. (1865: 522), Pleurolobus J. Saint-Hilaire (1812: 192) , Polhillides H. Ohashi & K. Ohashi (2019a: 71) , Puhuaea H. Ohashi & K. Ohashi (2019b: 280) , Sohmaea H. Ohashi & K. Ohashi (2018b: 159) , Sunhangia H. Ohashi & K. Ohashi (2019b: 285) , or Uraria Desvaux (1813: 122) , while D. dichotomum De Candolle (1825a: 336) should be transferred to Bouffordia H. Ohashi & K. Ohashi (in Ohashi et al. 2018a: 179). Only three exotic species, i.e. D. intortum ( Miller 1768: 11) Urban (1920: 292) , D. scorpiurus ( Swartz 1788: 107) Desvaux (1813: 122) , and D. tortuosum ( Swartz 1788: 107) De Candolle (1825a: 332) , together with D. uncinatum , remain in the genus Desmodium s. str. An updated key for naturalized Desmodium s. str. in China is given below.