Astragalus zibaishanensis sp. nov. (Fabaceae), a new species from Shaanxi, China

Astragalus zibaishanensis sp. nov. (Fabaceae) is described and illustrated from Shaanxi, China. This new species is similar to Astragalus monadelphus, A. xitaibaicus and A. neomonodelphus by having yellow petals, pseudomonadelphous androecium, and stipitate legumes, but can be distinguished by its stem 0.9–1.5 mm in diameter; leaflets 5–7, hairy adaxially and abaxially; calyx teeth triangular, ca. 0.5 mm long; standard 17–20 mm long; wings 18–21 mm long; keels 17–20 mm long; pistil glabrous; legume glabrous, with a stipe 10–11 mm long.

Astragalus zibaishanensis is unique in Astragalus by having pseudomonadelphous androecium. Phylogenetic analyses confirm that the new species is a member of A. sect. Cenantrum.

The nuclear ITS tree shows that A. zibaishanensis forms a clade with A. henryi, A. umbellatus, A. chilienshanensis, A. moellendorffii, A. przewalskii, A. monadelphus, A. xitaibaicus and A. neomonodelphus.