Ligusticopsis shaniana, a new combination separated from Peucedanum sensu lato (Apiaceae) on the basis of morphological and phylogenetic evidence

The genus Peucedanum sensu lato is one of the most taxonomically difficult taxa within Apiaceae, including many medically and economically valuable plants. Although previous studies performed several taxonomic revisions for this genus, the taxonomic position of many taxa in the genus still has not been satisfactorily resolved, especially those endemic to China. In this study, to clarify the taxonomic position of Peucedanum shanianum, we performed comprehensive morphological and molecular analyses for this species.

Morphological comparisons showed that Peucedanum shanianum has pinnate leaves, both pinnate and linear bracteoles, and numerous vittae in the mericarp commissure and each furrow, which are extremely similar to the genus Ligusticopsis but clearly different from Peucedanum sensu stricto, which has ternate leaves, linear-subulate or filiform bracteoles, a single vitta in a furrow, and two vittae on the commissure in a mericarp.

However, mericarps with filiform dorsal ribs and linear bracts can easily distinguish Peucedanum shanianum from other Ligusticopsis members. Furthermore, phylogenetic analyses based on plastome data and ITS sequences indicated that Peucedanum shanianum is only distantly related to Peucedanum sensu stricto members but nested in Ligusticopsis. Therefore, combining the evidence of morphology and phylogeny, we suggest that Peucedanum shanianum should be transferred to Ligusticopsis, and a new combination (Ligusticopsis shaniana) is proposed.