Phylogeny and delimitation of the Celastrales inferred from nuclear and plastid genes

A phylogenetic analysis of the Celastrales was performed using nuclear (18S, ITS 1, 26S rDNA) and plastid (atpB, matK, rbcL, trnL-F spacer) genes. In contrast to most previous studies, Celastrales and Malpighiales are resolved as being more closely related to one another than either are to Oxalidales. The Huaceae are well supported as the sister group to Oxalidales, not Celastrales, as had been previously proposed. The Lepidobotryaceae are unambiguously supported as sister to the clade consisting of Celastraceae and Parnassiaceae. The Parnassiaceae are well supported as members of an early branching lineage within Celastraceae, rather than as its sister group. Likewise, Pottingeria appears to be part of an early derived lineage of Celastraceae. Emplettridium is unambiguously supported as a derived member of Celastraceae, as are Brexia, Canotia, Siphonodon, Stackhousia, and Tripterococcus. Bhesa is unambiguously supported as a member of Malpighiales, though its relationships within the order remain unclear. Perrottetia should be transferred out of Celastraceae and into eurosids II, being closely related to Tapiscia and Dipentodon. These results help delimit the Celastrales and Celastraceae as morphologically more homogeneous taxa.