Bioscience Methods 2025, Vol.16, No.3, 137-153 http://bioscipublisher.com/index.php/bm 148 In practical applications, this molecular difference has been used to identify the species of seedlings and products. For example, by sequencing the COI of abalone samples in the Fujian market, it was quickly determined whether it was a local Haliotis diversicolor or an introduced Haliotis discus hannai, and it was found that some of the so-called "local abalone" were actually foreign Haliotis discus hannai, which improved market transparency. The species diversity of abalone in the southeastern coast of China is mainly reflected in the coexistence of local Haliotis diversicolor and foreign Haliotis discus hannai. Mitochondrial DNA analysis can effectively compare their population genetic characteristics, providing a basis for regional resource management and variety optimization. 6.2 Genomic divergence between introduced and native populations With the increase in global aquaculture exchanges, the genetic differences and potential impacts of introduced abalone species and local related species have attracted much attention. A typical case of China's abalone industry is the introduction of Haliotis discus hannai and the co-culture of local Haliotis diversicolor. Using mitochondrial genome and nuclear DNA markers to evaluate the differences between the two will help aquaculture management and species protection. In terms of mitochondrial DNA, the introduced Haliotis discus hannai and local Haliotis diversicolor have significant sequence differences, and the COI genetic distance is about 12%-15%, which is much higher than the general intraspecific differences. Therefore, mitochondrial markers can clearly distinguish between two different sources of abalone in the cultured population. For example, it has been reported that a small amount of Haliotis diversicolor mitochondrial haplotypes were detected in samples from a farm in Guangdong, suggesting that interspecies co-culture or mismixing occurred. The evaluation of differences in the nuclear genome is more complicated. Haliotis discus hannai and Haliotis diversicolor have different nuclear chromosome numbers: the former has 2n=36, and the latter has 2n=32. It is reported that hybridization can produce infertile offspring. The purity of the cultured population can be analyzed by high-throughput genotyping. For example, the application of 60K SNP chip detection found that most of the cultured individuals of Haliotis discus were clustered into the same category as the original Japanese population, but some individuals deviated from the principal component analysis, indicating that they may contain the gene components of Haliotis diversicolor. Further using the method of genome resequencing, the researchers found that about 2% of the nuclear genome fragments in two cultured populations of Haliotis discus in Fujian had the alleles of Haliotis diversicolor, indicating that hybridization may have occurred unintentionally during the culture process (Holland et al., 2022). Although these hybridization signals are weak, they should be taken seriously because continued gene introgression may change the genetic characteristics of the introduced species. In order to maintain the homozygous excellent traits of the Haliotis discus, farmers should avoid co-culture with Haliotis diversicolor and regularly test the purity of the strain through molecular markers. Another aspect worth evaluating is the genetic differences in adaptability between the two species. The wrinkled abalone is native to the cold temperate zone, while the variegated abalone is native to the subtropical zone. Their genomes may have differences related to temperature tolerance (Zhang et al., 2025). By comparing the enzymes encoded by the mitochondrial genes of the two, there are indeed differences in some heat resistance properties. For example, the variegated abalone COX enzyme has better tolerance to high temperatures than the wrinkled abalone (Xu et al., 2020). This also explains why the wrinkled abalone is prone to stress and even death during the high temperature period in summer, while the variegated abalone is more resilient. In aquaculture practice, the wrinkled abalone and the variegated abalone are sometimes crossbred to combine the advantages of both. However, due to the mismatch of chromosomes in distant hybridization, the survival rate and fertility of the offspring are very low (Hsu and Gwo, 2017; Li et al., 2024). Therefore, the more feasible strategy at present is to maintain the purity of the species, carry out targeted breeding separately, and meet the ecological needs of different species through environmental regulation. The differences in the genome between the introduced wrinkled abalone and the local variegated abalone are significant. The mitochondrial DNA can be easily distinguished, and the nuclear DNA also shows high heterogeneity. On the one hand, this difference gives us molecular tools to regulate seedlings and product varieties, and on the other hand, it
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