Phylogeny of Euclidieae (Brassicaceae) based on plastome and nuclear ribosomal DNA data

Euclidieae, a morphologically diverse tribe in the family Brassicaceae (Cruciferae), consists of 29 genera and more than 150 species distributed mainly in Asia. Prior phylogenetic analyses on Euclidieae are inadequate. In this study, sequence data from the plastid genome and nuclear ribosomal DNA of 72 species in 27 genera of Euclidieae were used to infer the inter- and intra-generic relationships within. The well-resolved and strongly supported plastome phylogenies revealed that Euclidieae could be divided into five clades. Both Cymatocarpus and Neotorularia are polyphyletic in nuclear and plastome phylogenies. Besides, the conflicts of systematic positions of three species of Braya and two species of Solms-laubachia s.l. indicated that hybridization and or introgression might have happened during the evolutionary history of the tribe. Results from divergence-time analyses suggested an early Miocene origin of Euclidieae, and it probably originated from the Central Asia, Pamir Plateau and West Himalaya. In addition, multiple ndh genes loss and pseudogenization were detected in eight species based on comparative genomic study.