Abstract
The genus Primula is extremely diverse in the east Himalaya-Hengduan Mountains (HHM) in China as a result of rapid radiation. In order to overcome the difficulty of morphological classification of this genus, we surveyed three plastid regions (rbcL, matK, and trnH-psbA) and two nuclear markers (ITS and ITS2) from 227 accessions representing 66 Primula species across 18 sections, to assess their discriminatory power as barcodes. We found that ITS alone or combined with plastid regions showed the best discrimination across different infrageneric ranks and at species level. We suggest rbcL + matK + ITS as the first choice at present to barcode Primula plants. Although the present barcoding combination performed poorly in many closely related species of Primula, it still provided many new insights into current Primula taxonomy, such as the underlying presence of cryptic species, and several potential improper taxonomic treatments. DNA barcoding is one useful technique in the integrative taxonomy of the genus Primula, but it still requires further efforts to improve its effectiveness in some taxonomically challenging groups.
Highlights
There is a critical need for rigorously delineated species for many theoretical studies and practical applications [1]
During this study we examined a total of 227 accessions of 66 Primula species from 18 of the 24 sections of the genus in China recognized by Hu [21]
All plastid markers were successfully amplified across all individuals, but amplification of ITS failed in two Primula species (P. virginis Lévl. and P. duclouxii Petitm.) and one accession of P. gemmifera Batal. (GXJ253, voucher: Hao940) in this study (S1 Table)
Summary
There is a critical need for rigorously delineated species for many theoretical studies and practical applications [1]. Using traditional morphology-based taxonomy is difficult to discover morphologically cryptic taxa [2]. Species that are the product of rapid radiations within single genera can represent suites of morphologically similar taxa that are difficult to distinguish both in the field and the herbarium [3]. DNA barcoding is a valuable addition to the taxonomic tool box. After 10 years development of DNA barcoding, it has been found that large genera with rapid evolutionary radiations still pose a significant challenge for a universal barcoding system [4,5,6]. In order to understand better the overall discriminatory power of the PLOS ONE | DOI:10.1371/journal.pone.0122903. In order to understand better the overall discriminatory power of the PLOS ONE | DOI:10.1371/journal.pone.0122903 April 13, 2015
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