The Mediterranean Mussel (Mollusca: Bivalvia) in Chile: Distribution and Genetic Structure of a Recently Introduced Invasive Marine Species.

The genetic characteristics of invasive species have a significant impact on their ability to establish and spread. The blue mussel (), native to the Mediterranean Sea, is a leading invasive species of intertidal coasts throughout much of the world. Here, we used mitochondrial DNA sequence data to investigate the genetic diversity and phylogeographic structure of invasive () versus native () populations of blue mussels in Chile. We evaluated whether genetic diversity in invasive populations could be explained by the genetic characteristics of the native sources from which they might be derived. A phylogenetic analysis confirmed two lineages of the invasive , i.e., the NW Atlantic and the Mediterranean lineages. We found no evidence of genetic structure in the invasive range of in Chile, most probably because of its recent arrival. We did, however, detect a spatial mixture of both lineages at sampling locations along the Chilean coast, giving rise to higher levels of genetic diversity in some areas compared to the population of native . The coastal area of the invasion is still small in extent (~100 km on either side of two large ports), which supports the hypothesis of a recent introduction. Further expansion of the distribution range of may be limited to the north by increasing water temperatures and to the south by a natural biogeographic break that may slow or perhaps stop its spread. The use of internal borders as a tool to minimise or prevent spread is therefore a genuine management option in Chile but needs to be implemented rapidly.