DNA Barcoding is becoming more and more attractive to biologists as a new method to aid in species identification. As a new technology, DNA Barcoding is very simple and easy to operate. It has been widely used in scientific research, especially in the field of conservation biology and investigation of biodiversity.
The core idea of DNA barcoding is based on the fact that species can be differentiated by short pieces of standard gene sequences. Generally, a genetic marker which could be used as a DNA Barcode should, on one hand, be conserved at some degree so that this genomic region could be amplified by universal primers for diverse taxa; on the other hand, be variable enough among taxa so that different species could be differentiated. It is very important to choose appropriate genetic markers for species identification. Recently the mitochondrial CO1 gene is already proving to be efficacious as a DNA barcode in a range of amimals.
The East Asian Endemic Cyprinid group is a group of cyprinid fishes whose speciation may be linked to the evolution of East Asian monsoon which has been affected by uplift of the Qinghai-Tibetan plateau. Because of rapid evolutionary radiation of the East Asian endemic group, we wonder that the mitochondrial cytochrome oxidase subunit 1 （CO1） gene could be an efficient marker for DNA barcoding of this group. In this study, we wanted to discuss the consequences and potential of the CO1 gene as a marker for phylogenetic reconstruction and DNA barcoding of this endemic cyprinid group.
The main work and conclusion of the present study were as the following:
(1) In order to testify the validity of the mitochondrial CO1 gene for species identification, we performed our research at different levels, such as Genus Culter, Subfamily Cultrinae and the East Asian endemic Cyprinid group. The analyses were focused on genetic distance and the phylogentic relationship. Genetic distance was calculated in MEGA3.0 software, and phylogenetic trees were constructed with PAUP and MrBayes software. In Genus Culter, genetic distance within species is obviously lower than that between species. And in the phylogenetic trees, all individuals of each species formed a clade. Then the conculsion was that mitochondrial CO1 gene was a good marker in Culter DNA barcoding. The conclusion was the same when the research group turned to Subfamily Cultrinae. In Cultrinae, genetic distance between species was much higher than that within species, and all the topology of trees constructed with different methods displayed that all the individual of each species formed a clade. From the study of Cultrinae, we can draw a conclusion that the mitochondrial CO1 gene can effectively support the species identification. When we met the data of genetic variation of East Asian Cyprinid group, the mean sequence divergences between groups were higher than that between Cultrinae taxa，then we could conclude that CO1 gene was a valid marker for DNA barcoding of East Asian endemic Cyprinid taxa. For the validation of DNA barcoding in the endemic group being supported, it provided a strong platform to construct the Bank of DNA barcoding.
(2) To assess support for the monophyly of East Asian endemic cyprinid taxa, we used the mitochondrial CO1 gene sequences for phylogenetic reconstruction of the family Cyprinidae. The phylogenetic analyses revealed three groups within Cyprinidae. The subfamily Danioninae was on the base, Barbine and Leuciscine formed sister group. Whitin Leuciscine, East Asian endemic Cyprinid taxa were recognized as a monophyly. Although the monophyly of Cultrins was strong supported, the relationships of each groups in East Asian endemic Cyprinid taxa were not well resolved. The result indicated that the mitochondrial CO1 gene sequence provided less phylogenetic information to resolve the relationship of this East Aisan cyprinid group.