<p>The genetic variation of the Mediterranean blue mussel, Mytilus galloprovincialis from the eastern coastline of the Adriatic Sea was investigated using polymorphic microsatellite markers. In total, 843 individuals were sampled from 18 populations representing a variety of coastal environments in Croatia, Bosnia-Herzegovina, Montenegro and Albania. Neutral loci revealed low levels of genetic structure in this continuously distributed species, while one outlier locus, MGE7, which may be under selection, provided strong evidence of genetic structure. The distribution of one of the alleles of this locus, MGE7²⁴³, was significantly correlated with latitude. A genetic seascape analysis using 9 environmental and 3 geospatial variables revealed a strong association between MGE7²⁴³ and three highly correlated environmental variables, maximum sea surface temperature, minimum salinity and maximum chlorophyll-a. This association was maintained for homozygous genotypes for the MGE7²⁴³ allele, but not for heterozygotes, providing further evidence that the locus MGE7 may be under selection or closely linked to a gene under selection. These findings highlight how previously unrecognised genetic structure can be identified through the use of genetic seascape approaches.</p>
Population genetic analysis of variation at five neutral microsatellite loci for Mediterranean mussels (Mytilus galloprovincialis) from 18 sites along the eastern Adriatic Sea revealed little or no spatial variation. In contrast, seascape genetics analysis revealed a pronounced locus-specific gradient in allelic and genotypic frequencies across the study region. At a sixth locus, MGE7, the frequencies of two alleles, MGE7 243 and MGE7 249 , were strongly associated, negatively and positively, respectively, with a single environmental variable -minimum salinity (minSAL). The frequency of the MGE7 243/243 homozygous genotype was strongly negatively associated with minSAL, whereas the frequencies of the MGE7 246/249 and the MGE7 249/249 genotypes were strongly positively correlated with minSAL. Interpretation of these pronounced gradients is confounded by the fact that minSAL and another environmental variable, maximum sea surface temperature (maxSST), are highly correlated (R = −.911) and are therefore not necessarily acting independently. BLAST searches of the MGE7 locus against M. galloprovincialis whole genome shotgun sequence returned an alignment with contig mg10_S01094 (accession UYJE01010330.1) and 7 predicted M. galloprovincialis proteins VDI82194.1 -VDI82200.1. Conserved domain searches revealed a similar structure to the transcriptional regulator Msx2-interacting protein.The BLASTp search also returned significant alignments to Msx2-interacting proteins in Mytilus coruscus, Crassostrea virginica, and Haliotis rubra. The existence of the MGE7 gradient highlights the role that environmental variation may play in retarding gene flow among wild M. galloprovincialis populations, and also how the success of collection of young mussels (spat) from one site and their transfer to another site (the farm) may be influenced by a single factor such as minSAL or maxSST on a localized scale.
<p>The genetic variation of the Mediterranean blue mussel, Mytilus galloprovincialis from the eastern coastline of the Adriatic Sea was investigated using polymorphic microsatellite markers. In total, 843 individuals were sampled from 18 populations representing a variety of coastal environments in Croatia, Bosnia-Herzegovina, Montenegro and Albania. Neutral loci revealed low levels of genetic structure in this continuously distributed species, while one outlier locus, MGE7, which may be under selection, provided strong evidence of genetic structure. The distribution of one of the alleles of this locus, MGE7²⁴³, was significantly correlated with latitude. A genetic seascape analysis using 9 environmental and 3 geospatial variables revealed a strong association between MGE7²⁴³ and three highly correlated environmental variables, maximum sea surface temperature, minimum salinity and maximum chlorophyll-a. This association was maintained for homozygous genotypes for the MGE7²⁴³ allele, but not for heterozygotes, providing further evidence that the locus MGE7 may be under selection or closely linked to a gene under selection. These findings highlight how previously unrecognised genetic structure can be identified through the use of genetic seascape approaches.</p>
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