Appraisal of the entire mitochondrial genome for DNA barcoding in birds

DNA barcoding based on a standardized region of 648 base pairs of mitochondrial DNAsequences from Cytochrome C Oxidase 1 (COX1) is proposed for animal species identification.Recent studies suggested that DNA barcoding has been effective for identifying 94% of birdspecies. The proposed threshold of 10 times the average intraspecific variation could be used forthe identification and delimitation of new species. As a different part of the mitochondrial DNAevolves at various mutation rates, they show a variety of capabilities to distinguish taxa tospecies level. In order to compare the efficiency of protein-coding genes (PCGs) in birds, thecomplete genome of 310 birds, including 12 mitochondrial genes (except ND6) and barcodingthe region of COX1, were examined. We concentrated on the intra- and inter-specific variationsand the degree of mutational saturation as criteria for our evaluations. Some genes like ATP8,ND2 and ND5 showed the greatest divergence in intra- and inter-specific variations. Theoverlap between intra- and inter-specific variability for all genes is still troublesome. Our resultsmay have been influenced by the sample size because our data were not representative of allbird species. More additional taxa may shed light more on DNA barcoding candidate genes.