Astragalus helanshanensis X. W. Li & B. Yang, sp. nov.

(Figs. 2–4)

Type: — Yushugou, Helan Mountain National Nature Reserve of Ningxia, arid gravelly desert steppe (105.902115 E, 38.429 046 N; 1365.93 m a.s.l.), April 25th 2024

Diagnosis: — Astragalus helanshanensis resembles A. borodinii but can be distinguished from A. borodinii by these morphological characteristics: the leaflets are always 2 pairs and opposite; the calyx is densely covered with white or black hairs, have white flowers and notched wing petals; the legume is 10–12 mm long, two-chambered, and has a partition.

Description:

Herb, perennial plant, 3–5 cm tall. The main stem is very short and reduced, with short branches in its lower part, and the entire plant is densely covered with appressed hairs. Leaves 2–4 cm; the petiole persists, and stipules are attached to the base of the petiole, triangular-ovate, 6–8 mm long, 4–6 mm wide, attached 1.5 mm above petiole base, and densely covered with short, soft hairs. The leaflets are always 2 pairs, mostly located at the upper third of the petiole, and opposite, obovate-elongate or ovate, with a short tip, 8–15 mm × 4–5 mm, and covered with appressed hairs on both sides, like the petiole. The inflorescence is a raceme, arising from the axils of leaves, with a peduncle about 4–8 mm in length, bearing 1–3 flowers; calyx is tubular, 13–16 mm long, densely covered with white or black hairs; calyx teeth are 5 in number, linear-lanceolate, 3–5 mm long. The flower is white; standard petal is narrow, obovate-elongate, 18–26 mm long, 6–7 mm wide, with a slight indentation at the apex; petals and the petiole are nearly equal in length; wings are about 15–20 mm long, with a rounded tip and notched; keel petals are a bit shorter than wings, with the petal length about half the petiole length. The fruit is a legume pod, ovate-elongate, 10–12 mm long, 2–3 mm high, flattened, having a hard back and densely covered with white appressed hairs. It has a beak, with a slight keel-like protrusion along the ventral suture, while the dorsal suture is slightly recessed or flat; it is bilocular.

Phenology: Flowering period is from May to June; fruiting period is from June to July.

Etymology: The species epithet comes from the name of the mountain range (He Lan Shan) where the species was discovered.

Vernacular name: The Chinese common name is “ ffiĔƜĦae ” (He Lan Shan Huang Qi)

Distribution and habitat: A. helanshanensis is limited in its distribution to the arid gravelly alluvial fans on either side of the southern end of the Helan Mountains. The habitat vegetation type is desert or desert steppe. Its distribution area stretches from the northern part of Yushugou, Helan Mountains, in the north, to the northern end of Qingtongxia City, Ningxia, in the south, forming a narrow and elongated distribution range.

The preliminary conservation assessment clearly indicates that A. helanshanensis are primarily distributed in the Helan Mountain National Nature Reserve. Their extent of occurrence is on the arid floodplain fan in the southern part of Helan Mountain, and the estimated area of occupancy is about 600 km 2. The estimated number of mature individuals is less than 2000. According to the IUCN standard, the Helan Mountain butterfly is classified as VU (Vulnerable).