Genetic Diversity among Takifugu rubripes and Takifugu obscurus in Different Regions of China Based on Mitochondrial DNA Sequencing Data

The purpose of this study was to explore the genetic diversity, genetic structure, and phylogenetic relationships of different cultured populations of Takifugu rubripes and T. obscurus in China, and to find a DNA barcode that can effectively distinguish one species from the other. In total, 120 T. rubripes and 130 T. obscurus individuals were collected from four and three different regions, respectively. Based on the sequences of the mitochondrial genes COI, COII, COIII, 16S rDNA , and Cytb , the genetic diversity and genetic evolution of the different populations of T. rubripes and T. obscurus were analyzed, and the genes with more polymorphic loci and high genetic diversity were selected for DNA barcoding for the identification of the two species. The results showed that Cytb had the highest genetic diversity, consistent with the genetic diversity of the other four genes. T. rubripes and T. obscurus have low haplotype and diversity indices, indicating that they may be subjected to variety of processes, such as inbreeding or domestication, that could lead to a continuous decline in diversity. From the perspective of differentiation and phylogeny, gene exchange may occur between some of the studied populations. Many populations of T. rubripes and T. obscurus showed limited variation, indicating that they reproduce according to the neutral evolution model, and that their diversity cannot be improved. In addition, the Cytb gene fragment used can effectively distinguish T. rubripes from T. obscurus , which can provide support for species identification and breeding in the future.