Astragalus baimaensis (Fabaceae), a new species from Yunnan, China

Based on an integrative analysis of morphological traits and molecular phylogenetic evidence, a new species of Astragalus (Fabaceae), A. baimaensis B. Jiang & Y. Z. Zhang, discovered during field investigations in the Baima Mountain region, Deqin County, Yunnan Province, China, is formally described. This species is defined by a unique combination of diagnostic morphological characters that unequivocally distinguish it from all previously documented congeners: it is completely glabrous throughout, with narrowly oblong leaflets, yellow flowers, and obliquely ellipsoid, glabrous, inflated legumes. The full chloroplast genome of A. baimaensis is 124,633 bp in length. Phylogenetic reconstructions based on plastid genomic data resolve A. baimaensis as sister to A. tongolensis, whereas analyses of the combined nuclear ITS and plastid (rbcL, matK) multilocus dataset support a closer evolutionary affinity between A. baimaensis and A. chilienshanensis. Despite these close phylogenetic relationships, the new species exhibits a distinct set of consistent morphological differences that clearly distinguish it from both putative relatives. The results highlight the considerable taxonomic value of variation in ovary pubescence within Astragalus and confirm that the presence or absence of trichomes on the ovary represents a stable diagnostic trait for species delimitation and infrageneric classification in this genus. This study adds to the known diversity of Astragalus and provides data for future phylogenetic and ecological studies.