不同DNA条形码在微口线虫属形态相近物种分类上的应用OA北大核心CSTPCD

In order to establish and improve the DNA barcoding identification method of marine nematode species,the dominant genus of free-living marine nematode,Terschellingia,was selected as the studying object.After morphological classification,DNA barcode was introduced to identify morphologically similar species in this genus.The species identification performance of mitochondrial cytochrome oxidase first subunit(COⅠ)gene,18S ribosomal RNA gene(rDNA)and 28S rDNA sequences was determined.Four morphologically different species of genus Terschellingia were identified and the DNA sequences of three species were obtained.The phylogenetic tree constructed with 18S rDNA and 28S rDNA supported the division of this genus into 6 taxa.The intraspecific and interspecific threshold of Kimura 2 parameter(K2P)varied between 0%to 2.5%and between 0.4%to 13.7%for 18S rDNA,respectively,while the intraspecific and interspecific threshold was zero and ranged from 20.5%to 84.6%for 28S rDNA,respectively.The MN18F-Nem_18S_R primer of 18S rDNA was the most suitable for being used as the DNA barcode of Terschellingia species,which may serve also as the distinguisher of the members of species complexes.The 28S rDNA sequence can be amplified successfully;however,the amplification met a relatively low success rate.COⅠ gene fragment cannot be successfully amplified among all species.We speculated that the primers available currently are not suitable for retrieving DNA sequence from the species in this genus.Our results indicated that DNA barcoding method can be used to identify morphologically similar species of free-living marine nematode,but their performance are different.