DNA Barcoding And Molecular Phylogeny Of Parnassia L.(Parnassiaceae)

DNA barcoding is a technique to identify species by using standardized DNA sequences. In this study, a total of133samples, representing43Parnassia species, were collected to test the effectiveness of four proposed DNA barcodes (rbcL, matK, trnH-psbA and ITS) for species identification. Our results demonstrated that1) all four candidate DNA markers have a maximum level of primer universality and higher than90%sequencing success.2) As a single DNA marker, the trnH-psbA region had the same highest species resolution with29/36, followed by the ITS region with28/36, the matK gene with23/38and the rbcL with14/37.3) The combination of the core barcode regions, matK+rbcL proposed by CBOL, gave the lowest species identification success (26/37) among any combination of multiple markers and was found unsuitable as DNA barcode for Parnassia. The combination of ITS+trnH-psbA achieved the highest species discrimination as31of34sampled species were distinguished, almost equal to the four-marker combination31/33and higher than any two or three marker combination including rbcL or matK. Based on the overall performance, the combination of ITS+trnH-psbA is proposed as the most suitable DNA barcode for identifying Parnassia species.DNA barcoding is a useful technique and provides a reliable and effective mean for the discrimination of Parnassia species, and in combination with morphology-based taxonomy, will be a robust approach for tackling taxonomically complex groups. In the light of our findings, we found among the three species not identified a possible cryptic speciation event in Parnassia.The genus, Parnassia is perennial herbs. Due to the complicated evolution process, patterns of morphological character are unstable, and the geographic differentiation is confused. It is a group of difficult classification. Phylogenetic trees were also constructed based on DNA barcode molecular data to reconstruct new phylogenetic relationships.Both DNA barcoding and morphological data analysis showed that:1) parnassia is a monophyletic group.2) Staminode characteristics may be result of repeated variability, different taxa were parallel evolution.3) According to staminodes features as the main basis for grouping is worthy of further research, cauline leaves and their morphology on group differentiates have important classification value.