Abstract
Smooth-shelled blue mussels, Mytilus spp., have a worldwide antitropical distribution and are ecologically and economically important. Mussels of the Mytilus edulis species complex have been the focus of numerous taxonomic and biogeographical studies, in particular in the Northern hemisphere, but the taxonomic classification of mussels from South America remains unclear. The present study analysed 348 mussels from 20 sites in Argentina, Chile, Uruguay and the Falkland Islands on the Atlantic and Pacific coasts of South America. We sequenced two mitochondrial locus, Cytochrome c Oxidase subunit I (625 bp) and 16S rDNA (443 bp), and one nuclear gene, ribosomal 18S rDNA (1770 bp). Mitochondrial and nuclear loci were analysed separately and in combination using maximum likelihood and Bayesian inference methods to identify the combination of the most informative dataset and model. Species delimitation using five different models (GMYC single, bGMYC, PTP, bPTP and BPP) revealed that the Mytilus edulis complex in South America is represented by three species: native M. chilensis, M. edulis, and introduced Northern Hemisphere M. galloprovincialis. However, all models failed to delimit the putative species Mytilus platensis. In contrast, however, broad spatial scale genetic structure in South America using Geneland software to analyse COI sequence variation revealed a group of native mussels (putatively M. platensis) in central Argentina and the Falkland Islands. We discuss the scope of species delimitation methods and the use of nuclear and mitochondrial genetic data to the recognition of species within the Mytilus edulis complex at regional and global scales.
Highlights
IntroductionSpecies delimitation in Mytilus complex biodiversity as well as for implementing conservation policies
The fifth and final group recognised by the BPP was a mixed Southern hemisphere clade, containing native mussels from the Auckland Islands (New Zealand Southern Ocean), Chile and Uruguay
Genetic sequence variation (COI) that has been used in previous studies where they addressed the evolutionary history of the Mytilus edulis complex (i.e. [18,67,70,71]) was analysed for the South American mussels in a geospatial framework (Geneland)
Summary
Species delimitation in Mytilus complex biodiversity as well as for implementing conservation policies. The accuracy of the method depends largely on the rate of speciation, the population size and the genetic variation used (number of informative sites or loci). These delimitation approaches remove the subjectivity associated with an individual researcher’s view of what constitutes a species, and have been helpful in solving taxonomic problems, those of closely related species (e.g., Lemer et al [11]), but are not yet widely applied
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