A taxonomic revision of Polystichum Roth sect. Sorolepidium (Christ) Tagawa

Polystichum (Dryopteridaceae) is one of the largest fern genera with long-standing taxonomy difficulties. Among them, P. sect. Sorolepidium has garnered considerable attention and particularly remained issues in species delimitation. In this study, a taxonomic revision of the P. sect. Sorolepidium was made based on comprehensive morphological studies that encompassed protologues and numerous specimens. We measured and recorded 26 morphological characters from 134 specimens (including 17 type specimens), and identified eight characters that played significant roles in species complex delimitation. Combining with previous molecular phylogeny studies, we redefined the range of P. sect. Sorolepidium, recognizing that this section consists of nine species belonging to two complexes. Polystichum glaciale complex includes P. glaciale, P. duthiei and P. integrilobum. P. moupinense complex includes P. castaneum, P. lachenense, P. moupinense, P. prescottianum, P. salwinense and P. shensiense. P. duthiei var. subbipinnatum was treated as a synonym of P. integrilobum, P. qamdoense var. elongatum and P. melanostipes as the synonyms of P. shensiense. P. qamdoense, P. paramoupinense, P. habaense, P. taizhongense were treated as synonyms of P. moupinense. P. yadongense, P. bomiense, P. tibeticum, P. pseudocastaneum were treated as synonyms of P. prescottianum. We finally provided key to the species and a list of examined specimens for each species.