Background The Peucedanum genus is the backbone member of Apiaceae, with many economically and medically important plants. Although the previous studies on Peucedanum provide us with a good research basis, there are still unclear phylogenetic relationships and many taxonomic problems in Peucedanum, and a robust phylogenetic framework of this genus still has not been obtained, which severely hampers the improvement and revision of taxonomic system for this genus. The plastid genomes possessing more variable characters have potential for reconstructing a robust phylogeny in plants. Results In the current study, we newly sequenced and assembled seven Peucedanum plastid genomes. Together with five previously published plastid genomes of Peucedanum, we performed a comprehensively comparative analyses for this genus. Twelve Peucedanum plastomes were similar in terms of genome structure, codon bias, RNA editing sites, and SSRs, but varied in genome size, gene content and arrangement, and border of SC/IR. Fifteen mutation hotspot regions were identified among plastid genomes that can serve as candidate DNA barcodes for species identification in Peucedanum. Our phylogenetic analyses based on plastid genomes generated a phylogeny with high supports and resolutions for Peucedanum that robustly supported the non-monophyly of genus Peucedanum. Conclusion The plastid genomes of Peucedanum showed both conservation and diversity. The plastid genome data were efficient and powerful for improving the supports and resolutions of phylogeny for the complex Peucedanum genus. In summary, our study provides new sights into the plastid genome evolution, taxonomy, and phylogeny for Peucedanum species.

Traditional classification based on morphological characters suggests that the genus Ostericum is closely related to Angelica, but molecular phylogenetic studies suggest that the genus Ostericum is related to Pternopetalum rather than Angelica. In this study, the plastomes of nine Ostericum species and five Angelica species were used to conduct bioinformatic and comparative analyses. The plastomes of Ostericum and Angelica exhibited significant differences in genome size, gene numbers, IR junctions, nucleotide diversity, divergent regions, and the repeat units of SSR types. In contrast, Ostericum is more similar to Pternopetalum rather than Angelica in comparative genomics analyses. In total, 80 protein-coding genes from 97 complete plastomes and 112 ITS sequences were used to reconstruct phylogenetic trees. Phylogenies showed that Angelica was mainly located in Selineae tribe while Ostericum was a sister to Pternopetalum and occurred in the Acronema clade. However, morphological analysis was inconsistent with molecular phylogenetic analysis: Angelica and Ostericum have similar fruit morphological characteristics while the fruits of Ostericum are quite different from the genus Pternopetalum. The phylogenetic relationship between Angelica and Ostericum is consistent with the results of plastome comparisons but discordant with morphological characters. The cause of this phenomenon may be convergent morphology and incomplete lineage sorting (ILS).

Hansenia trifoliolata Q.P.Jiang & X.J.He (Apiaceae), is described as new from Shaanxi Province, northwest China. The mericarp features of H. trifoliolata resemble H. himalayensis and H. phaea and molecular phylogenetic analyses (combining ITS and plastid genomes data) suggest that H. trifoliolata is closely related to the group formed by H. oviformis and H. forbesii. The new species H. trifoliolata has unique 3-foliolate leaves and differ from other Hansenia species in its leaves, umbel numbers and size. A comprehensive description of H. trifoliolata is provided, including habitat environment and detailed morphological traits.

The complete chloroplast genome of Allium macrostemon Bunge was determined. The length of the complete chloroplast genome is 153,158 bp. The whole chloroplast genome includes four regions: 82,700 bp long single-copy (LSC) and 17,600 bp small single-copy (SSC) regions separated by a pair of 26,429 bp inverted repeat (IR) regions. The overall GC content of the chloroplast genome is 36.7% and those in the LSC, SSC, and IR regions are 34.6, 29.1, and 42.7%, respectively.

The classification of species in the genus Pterocyclus has been a topic of concern, as they were initially considered members of Pleurospermum (Apiaceae) in the Flora of China. However, the intergeneric and infrageneric classifications of Pterocyclus and its allies, such as Hymenidium and Pleurospermum, have been controversial. To address these issues, we performed phylogenetic analyses using one nuclear marker (nrITS) from 167 accessions, including 137 species (including five species of Pterocyclus), and 105 plastid genes from 82 accessions representing 82 species (including five species of Pterocyclus) of Apiaceae. We used both maximum likelihood and Bayesian approaches to deduce phylogenetic relationships of Pterocyclus and its allies. Furthermore, we conducted morphometric analyses that specifically targeted the mericarp morphology, and compared the structural differences in their plastid genomes. Based on these findings, we suggest the following revisions to the classification of Pterocyclus and its allies: (i) Pterocyclus should encompass five species (Pterocyclus angelicoides, Pterocyclus forrestii, Pterocyclus rotundatus, Pterocyclus tibeticus, and Pterocyclus wolffianus), all of which are all monophyletic and placed in the Komarovieae; (ii) Pterocyclus rivulorum shows both phylogenetic and mericarp morphological similarities to Hymenidium apiolens and Hymenidium dentatum, which belongs to the Hymenidium Clade, thus we provisionally transfer it to Hymenidium; (iii) Pleurospermum longicarpum is considered conspecific with Pterocyclus angelicoides based on morphological descriptions in the Flora Xizangica; (iv) we describe and illustrate Pterocyclus tibeticus as a new species; and (v) Pterocyclus wolffianus should be recognized as a valid species and not considered a synonym of Pterocyclus forrestii.