Genome skimming provides evidence to accept two new genera (Apiaceae) separated from the s.l.

BACKGROUND

The s.l. genus, the backbone member of subfamily Apioideae, includes many medically and economically important plants. Although previous studies have proved that the genus was not a natural taxonomic unit and taxonomists also conducted several taxonomic revisions for taxa of this genus, classifications of numerous taxa of the genus still have not been satisfactorily resolved, especially for those endemic to China. Therefore, we conducted a comprehensive taxonomic revision of taxa within the polyphyletic s.l. genus in this study.

METHODS

We used two molecular datasets (103 plastomes and 43 nrDNA sequences) generated by genome skimming to reconstructed a reliable phylogenetic framework with high support and resolution. In addition, we also investigated the divergence time of core clade of endemic taxa.

RESULTS AND DISCUSSION

Both analyses failed to recover s.l. as a monophyletic group and robustly supported that , the representative of s.s., was distantly related to other s.l. members, which implied that these s.l. taxa were not "truly plants". Among these s.l. members, plastid-based phylogenies recognized two monophyletic clades, clade A (four species) and clade B (10 taxa). Meanwhile, obvious recognized features for morphology, plastome, and chromosome number for each clade were detected: dorsally compressed and glabrous mericarps with filiform dorsal ribs, winged lateral ribs, numerous vittae in commissure and each furrow, IRa/LSC border falling into 23 gene, an overall plastome size of 152,288-154,686 bp, and chromosome numbers of 2n=20 were found in clade A; whereas dorsally compressed and pubescent mericarps with filiform dorsal ribs, winged lateral ribs, numerous vittae in commissure and each furrow, IRa/LSC border falling into the 2 gene, an overall plastome size of 146,718-147,592 bp, and chromosome numbers of 2n=22 were discovered in clade B. Therefore, we established two new genera ( gen. nov. and gen. nov.) to respectively accommodate the taxa of clades A and B. Furthermore, molecular dating analysis showed that the diversification of clades A and B occurred in the early Pleistocene and late Pliocene, respectively, which may have been driven by the complex geological and climate shifts of these periods. In summary, our study impelled a revision of s.l. members and improved the taxonomic system of the Apiaceae family.