PHYLOGENETIC RELATIONSHIPS OF BRASSICACEAE SPECIES BASED ON MATK SEQUENCES

Abstract

The chloroplast gene matK, located in the intron of chloroplast trnK, encodes maturase, and variations of matK provide substantial resolution for phylogenetic analyses at intergeneric levels. Sequence data from 127 species (including subspecies and varieties) of Brassicaceae and one outgroup specie (Cleome gynandra) were used to construct the phylogeny of this family and elucidate the phylogenetic relationships therein using the neighbor-joining, maximum parsimony, and maximum likelihood methods. The phylogenetic results generally confirmed recently established tribal alignments and indicated that most of the 27 tribes were assigned to Lineages I–III. We found that the Orychophragmus violaceus complex, including O. violaceus, O. taibaiensis, O. hupehensis, and O. diffuses, which are native to China, should be subsumed under Lineage II, and was most closely associated with the tribe Brassiceae. Arabis was confirmed to be polyphyletic and one subclade shared a sister relationship with Boechereae, while A. alpine related species formed the other clade, which was not associated with any tribes. Previous analyses placed Conringia planisiliqua in tribe Brassiceae, but it was included within Isatideae in the current analyses, supporting previous hypotheses that it was a member of this tribe.