Plastid phylogenomics provide evidence to accept a new genus Pseudopeucedanum (Apiaceae) separated from Peucedanum s.l.

The species Peucedanum ledebourielloides, a medicinally important herb, has previously been placed in Peucedanum s.l. based on dorsally compressed mericarps with slightly prominent dorsal ribs and narrowly winged lateral ribs. However, this genus has now been re-delimited in a narrow sense, namely Peucedanum s.s., further recognized by ternate leaves and glabrous plants, so that the taxonomic position of P. ledebourielloides is unknown. To investigate the taxonomic position of this species, we sequenced and assembled the complete plastomes for two samples of P. ledebourielloides. Phylogenetic analyses based on 79 protein-coding genes showed that the samples of P. ledebourielloides formed a separate clade and were distant from Peucedanum morisonii, a representative member of Peucedanum s.s., implying that P. ledebourielloides cannot not be placed in Peucedanum s.s. Additionally, plastome comparisons and chromosome studies indicated the clear specificity of P. ledebourielloides. In particular, pinnate leaves and dorsally compressed mericarps densely covered with forked scabrous bristles, slightly prominent dorsal ribs, narrowly winged lateral ribs, and one vitta in each furrow and two vittae on the commissure clearly distinguished P. ledebourielloides from Peucedanum s.s. and other genera of Apiaceae. Hence, a new genus, Pseudopeucedanum gen. nov., was established to accommodate this species. Our results improve the taxonomy of the family Apiaceae and provide guidance for the taxonomic revision of other taxa that are difficult to place systematically.