First confirmed occurrence of the invasive mussel Mytella strigata (Hanley, 1843) in Guangdong and Hainan, China, and its rapid spread in Indo-West Pacific regions

Based on the morphological characters and the mitochondrial cytochrome oxidase subunit I (mtCOI) genes, 132 specimens of marine mussels from Guangdong Province and Hainan Province were identified as Mytella strigata (Hanley, 1843). This is the first report of this species in this region. Here, we investigated the worldwide dispersal and biogeographic patterns of M. strigata based on mtCOI haplotypes from both native and invaded regions. As a doubly uniparental inheritance species, the haplotype differentiation of female-lineage mtCOI (510 bp) and male-lineage mtCOI (433 bp) in M. strigata specimens was investigated. The result showed two haplogroups in both matrilinear and patrilinear haplotypes. Genetic relationships among haplotypes identified Colombia as the origin of M. strigata in Indo-West Pacific regions. We hypothesized the invasion of M. strigata to China, Singapore and Philippines happened at about the same time, around 2014 but diffused rapidly in recent years. We also proposed the ballast and biofouling were pathways of long-distance invasion for M. strigata, e.g., from South America to Indo-West Pacific regions, but the ocean and coastal currents promoted diffusion within small ranges. This study might provide useful information for the prevention and management of this invasive species.