Indigofera vallicola Huan C. Wang & Jin L. Liu, 2022

Liu, Jin-Li, Li, Shi-Gang, Yang, Feng & Wang, Huan-Chong, 2022, Indigofera vallicola (Fabaceae), a new species from Yunnan, southwest China, PhytoKeys 199, pp. 9-16 : 9

Indigofera vallicola Huan C. Wang & Jin L. Liu sp. nov.

Figs 1 , 2 , 3 , 4

Type.

China. Yunnan Province: Yimen County, Luzhi Town, Luzhijiang valley , Xiao Luzhi , 24°24'N, 101°34'E, alt. 1,320 m, 25 September 2021, Huan-Chong Wang et al. YM15303 (Holotype: YUKU!; isotypes: YUKU!)

Diagnosis.

I. vallicola is most similar to I. rigioclada Craib by sharing the procumbent habit, relatively small leaves and the similar flower shape, but it clearly differs from the latter by its usually 13-17-foliolate, flowers 3-5 mm long, calyx teeth triangular-lanceolate, and legumes 1-2 mm in diameter.

Description.

Dwarf shrubs, usually prostrate, 20-35 cm in height. Stems branched, brown, glabrescent, usually 1-2.5 mm in diameter. Branchlets nearly terete, 10-15 cm long, with dense appressed white and brown medifixed and symmetrically 2-branched trichomes. Leaves imparipinnate, 2-5 cm long, 1-2 cm wide, usually (7-)13-17-foliolate. Stipules lanceolate to subulate, 1-2 mm long. Petioles 0.2-0.4 cm long, petioles and rachis subterete, adaxially grooved, with appressed white and brown medifixed symmetrically 2-branched trichomes. Leaflets opposite, 0.2-1.2 cm long, 0.15-0.5 cm wide, adaxially green, abaxially gray, midvein abaxially prominent and adaxially impressed, secondary veins inconspicuous, both surfaces with white and brown medifixed symmetrically 2-branched trichomes; terminal leaflets obovate, apex rounded to truncate, and mucronate, base cuneate; lateral leaflets oblong or elliptic, apex rounded to truncate and mucronate, base rounded. Inflorescences racemose, axillary, 2.5-6 cm long. Peduncles 1-1.8 cm long. Bracts caducous, lanceolate to ovate-lanceolate, purple, ca. 0.2 cm long, abaxially with white medifixed trichomes, adaxially glabrous. Pedicels 1-2 mm long. Calyx funnelform, rarely cup-shaped, purple, outside with white and brown medifixed symmetrically 2-branched trichomes, glabrous inside; tube ca. 1 mm long; teeth 5, unequal, triangular-lanceolate, ca. 1 mm long, apex acuminate. Corolla pink; standard obovate, 3-5 mm long, 2-3 mm wide, apex mucronate, outside with white medifixed trichomes; wings spoon-shaped, 2.5-4.0 mm long, ca. 1 mm wide, outside pilose; keels 3-5 mm long, ca. 1 mm wide, outside pilose, with a small lateral spur. Stamens 3-5 mm long, anthers broadly ovoid, apex mucronate. Ovary hairy, style glabrous. Legumes linear, cylindric, 1.5-3.2 cm long, 0.1-0.2 cm in diameter, apex beaked, with white and brown medifixed symmetrically 2-branched trichomes. Seeds usually 6-8, oblong to rectangle, dark-brown, glabrous, 1-2 mm long, ca. 1 mm wide.

Phenology.

Flowering occurs from September to November, fruiting from October to December.

Distribution and ecology.

Indigofera vallicola is endemic to southwest China, where it has only been collected from two localities (ca. 45 km apart from each other) in central Yunnan to date: Xiao Luzhi (type locality) in Luzhijiang valley and Ainishan village in Shuangbai County. The climate in its habitat is seasonally hot and arid. In the type locality, I. vallicola occurs in the xerophilous scrubs or grasslands at elevations of 1200-1800 m, and its association include Phyllanthus emblica Linn. ( Phyllanthaceae ), Paliurus orientalis (Franch.) Hemsl. ( Rhamnaceae ), Dalbergia yunnanensis Franch. ( Fabaceae ), Symphoricarpos sinensis Rehd. ( Caprifoliaceae ), Duhaldea lachnocephala Huan C. Wang & Feng Yang ( Asteraceae ) (an endemic species described by Yang et al. (2022)), Pterygiella luzhijiangensis Huan C. Wang ( Orobanchaceae ), Silene otodonta Franch. ( Caryophyllaceae ), Spodiopogon sagittifolius Rendle ( Poaceae ), Heteropogon contortus (Linn.) Beauv. ex Roem. & Schult. ( Poaceae ) and Themeda caudata (Nees ex Hooker & Arnott) A. Camus ( Poaceae ).

Etymology.

The specific epithet is taken from the Latin " vallis " (valley) and the suffix "- cola " (dweller), referring to the habitat where the new species is found.

Additional specimens examined.

China. Yunnan: Shuangbai County, Ainishan, alt. 1,800 m, 22 October 1965, W. M. Zhu et al. 04195 (YUKU); Yimen County , Luzhi Town , alt. 1,250 m, 20 October 1965, W. M. Zhu et al. 4659 (YUKU); ibid., 3 October 2016, H. C. Wang et al. YM1274 (YUKU); ibid., 12 November 2019, H. C. Wang et al. YM8322 (YUKU) .

Taxonomic notes.

Indigofera vallicola is mainly characterized by having the prostrate habit, usually 13-17-foliolate leaves and relatively small (3-5 mm long) flowers. Morphologically, it is most similar to I. rigioclada Craib by sharing the procumbent habit, relatively small leaves and similar flower shape, but it clearly differs from the latter by its usually 13-17-foliolate (vs. 5-13-foliolate in I. rigioclada ), flowers 3-5 mm (vs. 8-10 mm) long, calyx teeth triangular-lanceolate (vs. triangular), and legumes 1-2 mm (vs. larger than 2 mm) in diameter. Indigofera vallicola is also more or less similar to I. henryi Franch. in its overall appearance, relatively gracile pedicels and shape of calyx. Nevertheless, I. henryi clearly differs from the former in having the linear stipules usually 5 mm long (vs. lanceolate to subulate, 1-2 mm long in I. vallicola ), leaves larger, 3-10 cm (vs. 2-5 cm) long, rachis of adaxially flattened, slightly winged (vs. grooved and without winged), leaflet blades 1.7-2.3 × 0.5-1.2 cm (vs. 0.2-1.2 × 0.15-0.5 cm), pedicels (2)3-6(-9) mm (vs. 1-2 mm) long, corolla much larger in size, white (vs. pink), with 7-9 × 5-6 mm (vs. 3-5 × 2-3 mm) standard and 7-9 mm (vs. 3-5 mm) long keels.

Indigofera vallicola is somewhat close to I. franchetii X. F. Gao & Schrire, an endemic species found from the dry-hot valleys of Jinsha River and its tributaries in southwestern China. Nevertheless, I. franchetii differs from I. vallicola in having 35-50 cm long branchlets, (11-)17-27-foliolate leaves ca. 5-10 cm long, racemes 5.5-11 cm long, peduncles 0.7-3.0 cm long, pedicels 0.5-1.0 mm long, calyces cup-shaped, standards oblong-elliptic, 7-8 mm long, legumes 2.5-4.0 cm long, 1.5-2.5 mm in diameter. The new species shows some similarities with I. chaetodonta Franch. in the habit, flower size, and calyx shape. However, I. chaetodonta is well differentiated from I. vallicola in having (5 or) 7- or 9-foliolate leaves 0.6-1.5 (-2.0) cm long, leaflet blades oblong to oblanceolate, 3.5-6 × 1.5-2.5 mm, adaxially nearly glabrous, standards broadly elliptic, 5-7 × ca. 4 mm, legumes 1.5-2.0 cm long, glabrous or with sparse appressed medifixed trichomes.

Figures

Figure 1. Indigofera vallicola Huan C. Wang & Jin L. Liu sp. nov. (Drawn by Jin-Li Liu) A habit B standard C wing D keel E calyx F anther G flower H leaflet I legume.

Figure 2. Indigofera vallicola Huan C. Wang & Jin L. Liu sp. nov. A habit B a portion of branchlet showing abaxial surfaces of leaflets C plants in fruiting stage D stipules E a portion of inflorescens F calyces G legume. Scale bars: 10 cm (A); 4 cm (C); 1 cm (B, G); 4 mm (E); 3 mm (F); 1 mm (D).

Figure 3. Indigofera vallicola Huan C. Wang & Jin L. Liu sp. nov. A standard B wing C keel D stamens and pistil.

Figure 4. A specimen (YUKU- 02024801) of Indigofera vallicola Huan C. Wang & Jin L. Liu sp. nov. collected in October 1965 from Ainishan village in Shuangbai County, southwest China.