Abstract
BackgroundThroughout the world, harvesting of mussels Mytilus spp. is based on the exploitation of natural populations and aquaculture. Aquaculture activities include transfers of spat and live adult mussels between various geographic locations, which may result in large-scale changes in the world distribution of Mytilus taxa. Mytilus taxa are morphologically similar and difficult to distinguish. In spite of much research on taxonomy, evolution and geographic distribution, the native Mytilus taxa of the Southern Hemisphere are poorly understood. Recently, single nucleotide polymorphisms (SNPs) have been used to clarify the taxonomic status of populations of smooth shelled mussels from the Pacific coast of South America. In this paper, we used a set of SNPs to characterize, for the first time, populations of smooth shelled mussels Mytilus from the Atlantic coast of South America.ResultsMytilus spp. samples were collected from eastern South America. Six reference samples from the Northern Hemisphere were used: Mytilus edulis from USA and Northern Ireland, Mytilus trossulus from Canada, and Mytilus galloprovincialis from Spain and Italy. Two other reference samples from the Southern Hemisphere were included: M. galloprovincialis from New Zealand and Mytilus chilensis from Chile. Fifty-five SNPs were successfully genotyped, of which 51 were polymorphic. Population genetic analyses using the STRUCTURE program revealed the clustering of eight populations from Argentina (Mytilus platensis) and the clustering of the sample from Ushuaia with M. chilensis from Chile. All individuals in the Puerto Madryn (Argentina) sample were identified as M. platensis × M. galloprovincialis F2 (88.89%) hybrids, except one that was classified as Mediterranean M. galloprovincialis. No F1 hybrids were observed.ConclusionsWe demonstrate that M. platensis (or Mytilus edulis platensis) and M. chilensis are distinct native taxa in South America, which indicates that the evolutionary histories of Mytilus taxa along the Atlantic and Pacific coasts differ. M. platensis is endangered by hybridization with M. galloprovincialis that was introduced from Europe into the Puerto Madryn area in Argentina, presumably by accidental introduction via ship traffic. We confirm the occurrence of a native M. chilensis population in southern Argentina on the coast of Patagonia.
Highlights
Introduction ofMytilus galloprovincialis, one of the most invasive mussel species, threatens native populations of Mytilus on a global scale [21, 22]
The level of differentiation observed between M. platensis and M. edulis was comparable to that between M. edulis and Atlantic M. galloprovincialis (FST = 0.427, on average) and was highest between M. platensis and M. trossulus and Southern Hemisphere M. galloprovincialis taxa (FST values as high as 0.797). These results indicate that the samples of Mytilus in Argentina were composed of three groups: (1) eight samples of native M. platensis, (2) a southern group represented by the UBC population of native Chilean blue mussel (M. chilensis), and (3) the population from Puerto Madryn (PMD) composed of hybrid individuals
We carried out a thorough population genetic analysis and, for the first time, we show that Mytilus populations from the Atlantic coast of South America and Isla Grande de Tierra del Fuego are strongly differentiated and belong to at least three taxa
Summary
Introduction ofMytilus galloprovincialis, one of the most invasive mussel species, threatens native populations of Mytilus on a global scale [21, 22]. We used a set of SNPs to characterize, for the first time, populations of smooth shelled mussels Mytilus from the Atlantic coast of South America. Aquaculture activities include the transfer of spat and live adult mussels between geographic locations, which may result in large-scale changes in the world distribution of Mytilus taxa [3,4,5]. Nuclear DNA markers including genome-wide single nucleotide polymorphisms (SNPs) can indicate geographic origin of interbreeding taxa when hybridization occurs either naturally or results from the introduction of mussels to non-native regions [14, 20]
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