DNA barcoding and phylogenetic relationships in Omphalogramma (Primulaceae) from the Hengduan Mountain region of China

Omphalogramma is a small genus with about 13 species and rather isolated distribution on high mountain range of the Himalayas. As the large degrees of similarity in morphological characters between species, it is difficult to distinguish closely related species in the genus. In this study, we used one nuclear ITS and other three chloroplast DNA markers (rbcL, matK, and trnH-psbA) to evaluate 39 accessions of Omphalogramma (Primulaceae) from the Hengduan Mountains, representing seven species. Our results showed that the discrimination power of the markers at the species level was 14.3% (rbcL), 28.4% (trnH-psbA), 42.9% (matK), and 100% (ITS). The mean value of genetic distance between species for ITS was more than 3-fold that of intraspecific distance; all species were distinguished. Species were differentiated by unique characters, and phylogenetic analysis showed that the Omphalogramma species formed two clear monophyletic clades comprising O. vinciflorum (bootstrapping: 96.8%) and remaining Omphalogramma species (bootstrapping: 97.5%). This study indicated that DNA barcoding is a useful technique in the phylogenetic and taxonomic description of Omphalogramma species.