The Phylogeny Study Of GRFT Clade Of The Brassicales

GRFT clade was recognized by Hall et al. based on molecularevidence, which including Gyrostemonaceae, Resedaceae,Forchhammeria, and Tirania. The Molecular systematic study ofBrassicales by Su et al. added two members to GRFT clade, Stixis andBorthwickia, and suggested Borthwickia as a new monotypic family.But the phylogenetic relationships and taxonomic status of the threemembers of GRFT clade, Forchammeria、Tirania and Stixis, are stillunsolved.Therefore, Our study using the Maximum Parsimony and Bayesiananalysis with ITS sequence reconstructed the phylogeny of the GRFTclade; Leaf epidermis of Borthwickia and Stixis were investigatedusing light microscopy (LM) and scanning electron microscopy (SEM);Twenty morphological characters of thirty-two taxa were selected forphylogenetic analyses. Using the Maximum Parsimony and Bayesianmethods, we analysed the combined morphological and five DNAregions data for the GRFT clade, the main results are outlined asfollows: 1. Maximum Parsimony (MP) and Bayesian analysis (BI) of ITSsequences and five DNA regions strongly support GRFT clade as amonophyletic clade. Within the GRFT clade, Gyrostemonaceae is theearliest-diverging lineage, Borthwickia is resolved as sister to therest clade, and other taxa formed a polyphyletic clade. Thephylogenetic relationships within the GRFT clade is congruent withprevious studies.2. Leaf epidermis of Borthwickia and Stixis were investigatedusing light microscopy (LM) and scanning electron microscopy (SEM).The results showed that: The characteristics of leaf epidermis ofStixis are very different from those of Capparaceae, Stixis is excludedfrom Capparaceae; The characteristics of leaf epidermis ofBorthwickia are differ from those of both Capparaceae and the othermembers of GRFT clade, which support Borthwickiaceae as a newmonotypic family.3. Neothorelia is embeded in the GRFT clade, and form a clade withStixis and Tirania with strong support in our Maximum Parsimony andBayesian analysis of the morphological and molecular data.Neothorelia was placed in tribe Stixeae of Capparaceae, withForchhammeria, Stixis, and Tirania. This study included Neothoreliain phylogenetic analysis for the first time.4. The four genera of tribe Stixeae, Forchhammeria, Neothorelia,Tirania and Stixis, are included in the GRFT clade in ourcombined analysis. Both them and Rsedaceae form a clade withstrong support. But because Neothorelia is not close with the otherthree genera, the monophyly of the tribe Stixeae is still uncertain.