﻿Astragalusbashanensis (Leguminosae), a new species from Central China

﻿Abstract A new species Astragalusbashanensis, from western Hubei Province, Central China is described and illustrated. The new species is morphologically similar to Astragalussinicus and A.wulingensis, but differs from both by its spreading pubescent indumentum on stems and petioles, longer petioles, white bracts, whitish or yellow corolla, longer claw of the keel-petal, hairy pods and smaller seeds.


Introduction
Astragalus L., consisting of ca. 2500 species, is one of the largest genera of vascular plant (Lewis et al. 2005). Astragalus sinicus L. (Chinese milk vetch) is native to the Yangtze River Basin of China and has been introduced to many countries as green manure, forage or ornamental plants and became widely naturalised, especially in Japan (Ohashi 2001(Ohashi , 2021Shimizu 2003). The corolla of Astragalus sinicus is usually purple, sometimes pink or pure white, but some scholars enlarged the colour range of the corolla to orange (Ho 1993), creamy-yellow or yellow (Xu and Podlech 2010). In the spring of 2022, during field investigations in Zhuxi County, the authors discovered an unknown Astragalus species. After comparing with several Astragalus species, we found that these specimens with yellow flowers are similar to A. sinicus L. and A. wulingensis J.X. Li & X.L. Yu by having a prostrate stem, umbellate racemes, outer surface of the calyx sparsely appressed white-pubescent and blackish pod. However, they differ from A. sinicus and A. wulingensis in habit and morphology of stem, leaf, stipule, bract, flower, fruit and seed (Table 1). Later, we found similar specimens with yellow flowers collected in western Hubei, Central China and stored under the name of Astragalus sinicus in some herbaria, which were also different from A. sinicus. After carefully checking specimens and literature (Ho 1993;Ohashi 2001Ohashi , 2021Zhu et al. 2007Zhu et al. , 2015Xu and Podlech 2010), we conclude that the Astragalus specimens collected in Zhuxi County and the aforementioned yellow-flowered herbarium specimens stored under the name of Astragalus sinicus represent a new species placed in Astragalus subgen. Astragalus sect. Lotidium Bunge and we describe and illustrate it here.

Astragalus bashanensis
Phenology. Flowering from late May to early July; fruiting from mid-June to late August.
Distribution and habitat. Populations of Astragalus bashanensis are known from Quanxi Town, Zhongfeng Town, Longba Town, Jiangjiayan Town, Piantoushan National Forest Park and Baguashan Provincial Nature Protection Area of Zhuxi County and it is also widely distributed in Shennongjia National Forest Park, western Hubei, Central China. It grows in roadside grassland, on mountain slopes, forest edges or under forest canopy at elevations from 600 to 2160 m.
Etymology. The specific epithet is derived from the type locality of the new species. Bashan is an abbreviation for Dabashan or Daba Mountains. Vernacular name. Ba Shan Huang Qi (Chinese). Conservation assessment. During our field investigations in 2021 and 2022, many populations of A. bashanensis have been found in Zhuxi County and Shennongjia Forest Region. The numbers of individuals of each population ranges from dozens to thousands. In addition, it is distributed along roadsides as a weed. We believe that it should have a much wider distribution than what is now known. Due to its wide distribution range and large population size, A. bashanensis is here recommended as Least Concern (LC) (IUCN 2022).

Results.
Astragalus bashanensis is most similar to A. sinicus and A. wulingensis in having prostrate stems, simple hairs, umbellate racemes, outer surface of calyx sparsely appressed white-pubescent and blackish and boat-like pods, but it can be easily distinguished from both by its spreading-pubescent indumentum on stems and petioles (vs. ascending-pubescent in A. sinicus; appressed-puberulent in A. wulingensis), long petioles (5-13 cm long), longer than the leaf rachis (vs. much shorter than the leaf rachis), white bracts (vs. green or flushed purplish), corolla whitish or yellow (vs. purple, pink to white or yellowish flushed purplish at apex), longer claw of the keel-petal (vs. much shorter), both sides of pods persistent pubescent (vs. glabrous or glabrate) and smaller seeds 1.5-1.8 mm long (vs. 2-3 mm long). The diagnostic features between A. bashanensis, A. wulingensis and A. sinicus are summarised in Table 1.