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Research Article
Astragalus bashanensis (Leguminosae), a new species from Central China
expand article infoSong-Zhi Xu‡, Qi-Liang Gan§, Xin-Wei Li|
‡ Nantong University, Nantong, China
§ Zhuxi Qiliang Biological Institute, Zhuxi, China
| Wuhan Botanical Garden, Chinese Academy of Sciences, Hubei, China

Corresponding author: Xin-Wei Li ( lixinwei@wbgcas.cn )

Academic editor: Hanno Schaefer
© 2023 Song-Zhi Xu, Qi-Liang Gan, Xin-Wei Li.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Xu S-Z, Gan Q-L, Li X-W (2023) Astragalus bashanensis (Leguminosae), a new species from Central China. PhytoKeys 219: 49-55. https://doi.org/10.3897/phytokeys.219.96916
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Abstract

A new species Astragalus bashanensis, from western Hubei Province, Central China is described and illustrated. The new species is morphologically similar to Astragalus sinicus 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.

Keywords

Astragalus bashanensis, Central China, new species, taxonomy

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, 2021; Shimizu 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 2001, 2021; Zhu et al. 2007, 2015; Xu 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.

Materials and methods

Astragalus specimens were collected in Shennongjia and Zhuxi County of Hubei Province. Comparisons with its relatives were made by consulting specimens stored in PE and HIB, fresh material in the field and some virtual specimen databases (CCAU, KUN, IBK, IBSC, CVH and JSTOR). All morphological characters were measured with dissecting microscopes and were described using the terminology suggested by Harris and Harris (1994).

Taxonomic treatment

Astragalus bashanensis Q.L.Gan, X.W.Li & S.Z.Xu, sp. nov.

urn:lsid:ipni.org:names:77312598-1
Figs 1, 2

Diagnosis

Astragalus bashanensis Q.L.Gan, X.W.Li & S.Z.Xu is similar to Astragalus sinicus L. and A. wulingensis J.X. Li & X.L. Yu, but the new species can be easily distinguished from both by its spreading pubescent indumentum on stems and petioles, petioles longer than the leaf rachis, white bracts, whitish or yellow corolla, longer claw of the keel-petal, persistent pubescence on both sides of pods and smaller seeds.

Figure 1. 

Astragalus bashanensis sp. nov. A population B branches C root D, E, F leaves.

Type

China. Hubei Province: Zhuxi County, Quanxi Town, Hongyangou Village, on Hengduan Mountain, alt. 840 m, 32°4'8.5"N, 109°39'26.33"E, June 2022, Q. L. Gan 3295 (holotype: PE!; isotype: HIB!).

Paratypes

China. Hubei: Zhuxi County, Jiangjiayan Town, Yanjiajie Village, Piaoshiyan, 3 June 2022, Qi-Liang Gan 3294 (PE!); Quanxi Town, Hongyangou Village, Hengduan Mountain, 7 June 2022, alt. ca. 840 m, Qi-Liang Gan 3295 (PE!); Biaohulinchang, at the foot of Piantou Mountain, alt. 1200 m, Qi-Liang Gan 3287 (PE!); Shennongjia, Dashennongjia, south slopes, alt. 2800 m, flower white, 5 July 1976, Shennongjia Exped. 10718 (PE!, HIB!); Guanmenshan, Shibangou, alt. 2160 m, slopes, 5 August 1976, Shennongjia Exped. 10790 (PE!, HIB!); Guanmenshan, alt. 2150 m, under forests, 5 August 1976, Shennongjia Exped. 10835 (PE!, HIB!); Songluoxiang, Longchahe, Huilongsi, alt. 2000 m, roadside grassland, 2 September 1976, Shennongjia Exped. 22834 (PE!, HIB!).

Figure 2. 

Astragalus bashanensis sp. nov. A adventitious roots B petioles C stipules D flowering plant E, F umbellate racemes G bracts H calyx I opened calyx J, K corolla K1 standard K2 keel-petal K3 ovary and stamens K4 wings L pedicels M young fruits N mature fruits O seeds.

Description

Herbs annual or biennial. Primary root slender, 8–12 cm long, yellowish; nodules sparsely on lateral roots. Stem 20–70 cm long, spreading white pubescent; branches from base, prostrate or decumbent, rooting at nodes, internodes 3–8 cm long. Stipules free, triangle-ovate, 3–5 mm long, base 3–4 mm wide, glabrous or with few hairs at apex. Petioles 5–13 cm long, longer than the leaf rachis, spreading-white-pubescent, thickened at base. Leaves odd-pinnate, 7–9-foliolate, rarely even-pinnate 10-foliolate, 5–13.5 cm long, 2.5–6.3 cm wide; rachis sparsely pubescent; leaflets broadly elliptic or broadly obovate, 0.8–3.1 cm long, 0.7–2.4 cm wide, apex emarginate, base rounded or broadly cuneate, margin entire, adaxial surface glabrous, abaxial surface sparsely appressed white-pubescent, the hairs on nerves denser; petiolules less than 1 mm long, densely pubescent. Racemes umbellate, 6–20-flowered, in one, rarely two umbels; peduncles axillary, erect, 10–20 cm long, up to 15–26 cm in fruit, sparsely pubescent; bracts ovate ca. 0.5 mm long, ciliate, white, deciduous after anthesis; pedicels 0.5–1.5 mm long, white-pubescent; flowers spreading or nutant. Calyx tubular, out surface sparsely appressed white-pubescent; tube ca. 3 mm long; lobes 5, subulate, 2.6–3.2 mm long, lower two shorter than the tube, upper three longer than or as long as the tube. Corolla whitish, creamy-yellow, yellowish or deep yellow; standard obovate, 10–13 mm long, 4–5 mm wide, apex emarginate, base broadly cuneate with short claw; wings 8–10 mm long, claw scarcely shorter than the limb, limb oblique-oblong; keel-petal 7–9 mm long, limb crescent-shaped, base auriculate, claw ca. 2/3 of limb length. Stamens (9) + 1, white, ca. as long as the keel-petal. Ovary narrowly linear, both sides white pubescent; style filiform, glabrous. Pod linear, lateral oblate and green when young; mature pod swelling into boat-like, blackish, 2.5–3 cm long, ca. 4 mm wide, both sides persistent white-pubescent, apex with a thicker beak ca. 1 cm long. Seed dark green-brown, lustrous, orbicular-reniform or reniform, 1.5–1.8 mm long.

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.

Table 1.
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Morphological comparisons of Astragalus bashanensis, A. wulingensis, and A. sinicus.

Characters A. wulingensis A. bashanensis A. sinicus
Stems 30–80 cm long 20–70 cm long 10–30 cm long
Stipules ciliate glabrous or with few hairs at apex ciliate
Petioles 3–5 cm long, much shorter than the leaf rachis 5–13 cm long, longer than the leaf rachis 0.5–4 cm long, much shorter than the leaf rachis
Indumentum on stems and petioles sparsely appressed-pubescent spreading-pubescent sparsely ascending-pubescent
Leaflets 1.5–2.8 × 0.8–1.1 cm 0.8–3.1 × 0.7–2.4 cm 0.5–1.7 × 0.3–1.3 cm
Bracts green or flushed purplish white green or flushed purplish
Calyx tubular, ca. 7 mm long tubular, 5–6 mm long campanulate, 3–5 mm long
Lobes of calyx subulate, 3–4 mm long subulate, 2.6–3.2 mm long lanceolate, 1–2 (–3) mm long
Corolla colour white or yellow, apex flushed purplish whitish, creamy yellow, yellowish or deep yellow purple, pink to pure white
Claw of keel-petal ca. as long as the limb ca. 2/3 length of the limb ca. 1/3 length of the limb
Wings 10–13 mm long, claw as long as the limb 8–10 mm long, claw scarcely shorter than the limb 7–11 mm long, claw ca. 1/3 length of the limb
Pods 3–4 cm long, glabrous 2.5–3 cm long, both sides persistent-pubescent 1.2–2 cm long, glabrous or glabrate
Seeds orbicular-deltoid, 2–2.2 mm long, red-brown orbicular-reniform or reniform, 1.5–1.8 mm long, dark green-brown reniform, 2–3 mm long, green-brown

Acknowledgements

We thank Professor Xiang-Yun Zhu for providing some photos of specimens and important literature.

References

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