The small abalone (Haliotis diversicolor) is an extremely distinctive cultured species in Taiwan. The present study used the random amplified polymorphic DNA (RAPD) technique with the P3 locus pattern, to compare the genetic variation of small abalone collected from 2008 to 2021. Early results showed that small wild abalone had 8-12 polyphenotypic amplification bands, primarily between 0.1 kb and 1.0 kb, whereas the polyphenotypic amplification bands of cultured small abalone were mostly 1.0 kb, 0.8 kb, and 0.65 kb. In addition, some cultured small abalone samples presented differences in band depth (e.g., copy number variation, CNV) and also showed band omission, indicating that the genetic variation and survival rate of cultured small abalone have declined as the result of constant artificial selection.
The industry has improved the survival rate of cultured seedlings by introducing abalones from other geographic populations, which demonstrates that it is feasible to enhance the genetic variation of species through hybridization and to subsequently strengthen the ability of organisms to adapt to a changing environment. However, the samples collected in recent years have begun to show a reduction in genetic diversity and a trend in homogeneity of genetic variation.
In summary, this study demonstrated that genetic variation can be improved by selecting breeds with higher genetic variation for crossbreeding; however, the preservation, selection, and management of breeds with a higher degree of genetic variation are key factors for the success of this industry. Moreover, it is equally important to maintain and sustain the benefits of crossbreeding, in order to promote excellent breeding performance in the cultured organisms, including growth, cold tolerance, and heat resistance, among other factors.