engleski

Genetic identification and population analyses of mussel Mytilus galloprovincialis along the eastern Adriatic coast: heterozygote/hybrid characterization

Mussels Mytilus spp. belong to a group of key species in marine, coastal ecosystems. This work demonstrated the dominant presence of Mediterranean mussel M. galloprovincialis along eastern Adriatic coast (22 sites), from Limski kanal to Dubrovnik. Morphological variations of shell measurements and shape of sampled mussel specimens were inside normal values for M. galloprovincials. However, molecular analysis gave some new insight into the genetic diversity of Adriatic mussels. Nuclear marker Me 15/16 of the adhesive byssus protein is suitable to distinguish mussels of Mytilus edulis complex: M. edulis is characterized with allele E, M. trossulus with allele T and M. galloprovincialis with allele G. Among the 110 analysed mussels of the Croatian Adriatic Sea populations 2 specimens showed a heterozygote GE and GT genotypes, while all others were identified as homozygotes GG. The AFLP analyses of GT, GE and GG mussels also showed differences at two other loci, mac-1 and EFbis. The phylogenetic analysis based on alpha and beta 5S rDNA clones showed grouping of Adriatic M. galloprovincialis in three clusters ; GG genotypes form one group with referent M. galloprovincialis, GE genotypes grouped with M. edulis and GT genotypes with M. trossulus. The presence of the E alleles of all three loci at low frequency in M. galloprovincialis mussels could be explained by introgression since M. edulis and M. galloprovincialis are known to hybridise and exchange genes in the European contact zone. The presence of the T alleles is very surprising. This could be explained by introducing of T alleles as a result of accidental entrance of M. trossulus with ballast waters. However, we could not exclude the presence of relict M. gallorovincialis population carrying T allele. CoI sequences analysis identified typical Adriatic haplotypes (group 1. and 2.) with presence of M. edulis complex (M.g., M.t. and M.e.) Atlantic/Baltic haplotypes. The unexpected haplotypes detected can be explained by Mytilus maternally and paternally inherited mitochondrial genomes, recent hybridization and/or relict of an ancient stock introgression. Further detailed morphometric and genetic analyses on larger numbers of specimens are needed to clarify the processes underlying origin and evolution of Mediterranean mussels M. galloprovincialis.

Heterozygotes; hybrids; Me15/16; 5S rDNA; barcoding

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