Genetic diversity of Southern hemisphere blue mussels (Bivalvia: Mytilidae) and the identification of non-indigenous taxa

The taxonomic and evolutionary affinities of Southern hemisphere smooth-shelled blue mussels are unclear, with studies using different marker types having identified different relationships among various geographic regions. Using an existing and a new molecular assay, the present study builds on previous work to test the distribution of blue mussels native to and introduced to the Southern hemisphere. Populations of Mytilus were sampled from New Zealand, Australia, and Chile. The nuclear-DNA marker Me 15/16 was used to identify the taxonomic status of 484 individuals. A new restriction fragment length polymorphism (RFLP) assay was used to identify the hemisphere of origin for a subset of Mytilus galloprovincialis. The Me15/16 marker identified 478 pure M. galloprovincialis from Southern hemisphere sites and six Mytilus edulis/M. galloprovincialis hybrids from the Auckland Islands (New Zealand) and Chile. A cytoplasmic RFLP identified Northern hemisphere M. galloprovincialis in almost every Southern hemisphere region. The presence of native M. galloprovincialis at high latitudes (up to 52 degrees S) has implications for our understanding of environmentally induced selective constraints considered to determine species distributions. Widespread occurrence of invasive Northern hemisphere blue mussels in the Southern hemisphere is documented for the first time. Identification of inter-specific hybrids (M. edulis x M. galloprovincialis) in Chile and in the Auckland Islands (subantarctic New Zealand) illustrates that environments ranging from international ports to remote protected locations are vulnerable to bioinvasion. (C) 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 898-909.