DNA Barcoding Of The Pleuronectiformes And Genetic Diversity Of Paralichthys Olivaceus In China

In present study, DNA barcoding—sequencing a standard region of the mitochondrial cytochrome c oxidase 1 gene (CO1) was used to providing species-level identifications of 50 species of Pleuronectiformes. Genetic diversity and structure of Paralichthys olivaceus over the Bohai Sea, Yellow Sea and East China Sea were analyzed using the sequences of the mitochondrial control region gene. The main conclusions and hypotheses of the present study are as follows:1.31 species,76 sequences of Pleuronectiformes were sequenced (barcoded) for a 652 bp region of the mitochondrial cytochrome oxidase subunit I gene (CO1), Most species were represented by multiple specimens.83 sequences were downloaded from Genbank and 159 sequences were generated. For the species level analysis, nucleotide-sequence divergences were calculated using the Kimura-two-parameter (K2P) model,the distances of most intra-species were zero,except Pseudorhombus arsiu, Pardachirrus pavoninus, Arnoglossus laterna, Cynoglossus puncticeps, Cynoglossus itinus, Zebrias quagga. Mean distance of intra-species was 0.04 and mean distance of inter-species was 0.195.The mean distance of intra-species was much greater than the mean distance of inter-species, we conclude that sequence variation in the CO1 barcode region will be very effective for discriminating species of Pleuronectiformes. The six species with large mean distance of intra-species are sampled from different locations and identified by different researches. The fish of Pseudorhombus can not be clustered together, so do Cynoglossus and Arnoglossus. Which suggest that further evaluation is needed for discrimination of species of Pseudorhombus, Cynoglossus and Arnoglossus.We support the point that Cynoglossus abbreviatus and Cynoglossus purpureomaculatus should be a single species based on 16SrRNA,ITS1 and CO1 gene.The Aesopia cornuta and Solea ovate were clustered together suggesting that they were possible synonymy. 2. Fragments of 602bp at the 5 end of mitochondrial DNA control region were sequenced for 107 individuals from six localities over Bohai Sea, Yellow Sea and East China Sea. Within the aligned 602bp bases,104 nucleotides were variable, and a total of 66 haplotypes were identified. The haplotype diversity (Hd) was 0.986(0.879-0.990), the nucleotide diversity(π) was 0.02483(0.01449-0.02603). Paralichthys olivaceus of China show a high genetic diversity in marine fishes. The AMOVA analysis indicated that the genetic variation mainly occurred within populations. The mismatch distribution of haplotypes, together with the selective neutrality test of Fu's Fs (-24.17135, P=0.00), suggest that a recent population expansion of Paralichthys olivaceus have been occurred,The expansion time is between 56Kyr and 144Kyr ago. Three distinct lineages were detected, but lack of phylogeographical structure.As Paralichthys olivaceus in Yantai were composed of the most abundant gentic diversity in the six sampled sites, Yantai should be as priority conservation areas.