Molecular classification of Barbeyaceae (Barbeya oleoides Schweinf.) using four different DNA barcodes

Despite many efforts to determine the phylogenetic relationship between Barbeyaceae and other families of Rosales, the sister relationship of this family has remained unclear. Barbeya oleoides, which is currently the only species in the family Barbeyaceae, and native to Somalia, Ethiopia, and the Arabian Peninsula were collected from Wadi Turbah Zahran northwestern of Al-Baha City, southwestern Saudi Arabia (20°14’N, 41°15’E). To study the sister relationship of Barbeyaceae and the other families of Rosales, the complete chloroplast sequences were used for phylogenetic analysis. In addition, four standard DNA barcodes (the internal transcribed spacer 2 (ITS2), ribulose 1,5-biphosphate carboxylase (rbcL), maturase K (matk), the intergenic spacer region (trnH-psbA)) were used to test for their quality in identifying phylogenetic relationship of the studied families. Sequence analysis of the complete chloroplast sequences showed that Rosales clade has two subclades and clearly discriminated all families within this order. This is the first report of a partial ITS2 locus sequence in B. oleoides. The partial ITS2, rbcL, matk, and gene sequences discriminate B. oleoides of the Barbeyaceae family from the closely related plant families: Cannabaceae, Rosaceae, Rhamnaceae, Urticaceae, Moraceae, Elaeagnaceae, Dirachmaceae, and Ulmaceae. In contrast, the partial trnH-psbA sequence of B. oleoides did not show any homology to the available DNA sequence of plant families in GenBank, suggesting that it is more suitable as DNA barcode for variations within one species.