Geographic origin and post-invasion genetic divergence of Mytilus galloprovincialis in China

Biological invasions serve as natural experiments to investigate how species adapt to novel environments. The Mediterranean mussel (Mytilus galloprovincialis), a highly successful marine invader and strong biofouler, has formed dominant populations along the coast of China. However, its genetic origin, population structure, and the consequences for the genetic diversity of invasive and native populations remain unclear. To address this, we employed a 60 K SNP array to genotype 320 individuals sampled from seven geographic populations, along with 112 reference samples. The results indicate a clear genetic affinity between Chinese and Mediterranean populations (F_ST < 0.05), while moderate differentiation was observed from Atlantic populations (F_ST > 0.05), supporting a Mediterranean origin. Genetic differentiation was observed in Dalian, whereas Lianyungang served as a key gene flow sink from both Mediterranean origins and nearby invasive populations. Moreover, using just 20 SNPs with a Support Vector Machine (SVM) model yielded 84 % classification accuracy, closely matching the full array's performance. Our findings provide novel insights into the invasion history and post-invasion genetic dynamics of M. galloprovincialis in East Asia and highlight the utility of SNP tools for species identification, population monitoring, and pollution-related biomonitoring in marine ecosystems.