Research On The DNA Barcode Of The Passerine Birds In East Asia?

The Taxonomy is fundamental to the recognition of biological science.Only when we have the full knowledge of how to identify the species correctly,biological research could be carried out properly.Accurate and rapid identification of species has become a hot topic in the taxonomy community for years.DNA Barcoding technique,as a new method for rapid identification for biological species,has been widely used.since 2003.Ideal barcodes are standardized DNA sequences,sufficiently variable,and easily amplified.For birds,the study on 260 species of North American suggested a 648 bp region of cytochrome c oxidase I(CO1)in the mitochondrial DNA(mtDNA),might serve as DNA barcode for birds.Nevertheless,birds of East Asia and North American have very different evolutionary history.Whether the “standardized DNA barcode” generated from North America,could also work for the birds in East Asian,is a question worth exploring.The passerine birds are rich in species,accounting for more than half of the whole number of bird species.It is an important part of the world's wildlife resources and it is significant for the protection of global biodiversity.Many comprehensive studies have been conducted on the breeding,singing,ecology,and behavior of passerine birds.However,due to the large number of species,the differences in the morphology of some species are very small,passerine birds are difficult to identify.The morphological variation is significant.Therefore,the species identification,taxonomic status,and phylogenetic relationships of many birds in the passerine form have attracted much attention and have caused much controversy.Therefore,it is of great significance to explore whether DNA barcodes can be used for species identification of passerine birds in East Asia.The research aims to answer two questions:1)Does the barcoding gap exists in birds of east Asia? 2)How reliable is the DNA barcodes used to identify the bird species in east Asia?We chose Passeriformes as the subjects of study.Bardcode sequences were explored and selected from NCBI(www.ncbi.nlm.nih.gov)and BOLD(www.barcodinglife.org),and then,more samples were sequenced in our lab.All the sequences were analyzed on the interspecific and intraspecific category,to calculate the genetic divergence at different taxonomic levels.We collected 4525 barcode sequences of 427 species,belonging to 156 genus,48 families.Moreover,275 barcode sequences were new added to the database,involved 72 species in 52 genus,19 families.Results showed that the mean intraspecific genetic divergence is 1.355%,variation range is 0-17.5%,77.8%of the distances are below 2%.However,the mean interspecific genetic divergence is 10.557% with a range between 0 and 18.8%,92.2% of the genetic distances were from 5-16%.The barcode differences between species are,on average,7.79 times higher than the differences within species.Barcoding gap doesn't exist in Passeriformes of East Asia.The “Barcoding gap” is an artifact of insufficient sampling across taxa.Compared with North American results,interspecific and intraspecific CO1 distances are greater.This is consistent with the evolution of birds in East Asia.Due to the different evolutionary history,the thresholds that apply to North America do not apply to the identification of passerine birds in East Asia.We propose a threshold of 4.9%.Under this threshold,the identification success rate of birds in East Asia is the highest,which is 94.2%.We suggest that DNA barcoding can be used to identify most species of the Passeriformes of East Asia,but not for recently diverged species.The intraspecific distance of birds in East Asia is much higher than that of birds in North America.This shows that the protection of birds in East Asia should not only focus on the protection of species,but also on the protection of genetic diversity.Implement multi-level and more comprehensive biodiversity conservation measures.