Linkage studies in Mytilus edulis, the mussel

Abstract

Electrophoretic data at 10 allozyme loci from the offspring of six single pair matings of Mytitus edulis were analysed for linkage. Significant deviations from expected octopine dehydrogenase (Odh)/phosphoglycerate kinase (Pgk) and leucine aminopeptidase (Lap )/esterase D (EsD) di-locus genotype frequencies were evident in two families. In the former case, the recombination frequency was 0.463 suggesting epistasis but in the latter case a recombination frequency of 0.022 indicated almost complete linkage between the Lap and EsD loci. Other loci showing significant linkage were Odh JLap and Odh /glucose phosphate isomerase (Gpi). Based on these data and other known linked loci in Mytilus a linkage group comprising Lap, EsD, Odh, mannose phosphate isomerase (Mpi) and possibly also Gpi is proposed. It is noted with interest that the closely related taxa M. edulis, M. galloprovinciatis and M. trossulus are distinguished by significant allele frequency variations almost exclusively at loci in this linkage group.

Genetic variability in Irish populations of the invasive zebra mussel, Dreissena polymorpha: discordant estimates of population differentiation from allozymes and microsatellites

“…Since larvae or newly settled zebra mussels were not analysed in our study, we are unable to test the model. There is the possibility that the three loci, EST‐D , GPI and OPDH at which the majority of significant F IS values were observed, form part of a 5‐locus linkage group ( GPI, OPDH, LAP, EST‐D and MPI ) as reported for the marine mussel, Mytilus edulis (Beaumont, 1994) and that selection acts against heterozygotes at the linked loci. However, this must be discounted since there was no evidence for significant linkage disequilibrium between any locus pair.…”

Evolutionary implications of discordant clines across the Baltic Mytilus hybrid zone (Mytilus edulis and Mytilus trossulus)

“…Interestingly, Väinö lä and Hvilsom (1991) described concordant clines for four diagnostic allozymes across a relatively narrow transition zone of 100 km along the Øresund region. Subsequent work has shown that these loci do not segregate independently because they belong to the same linkage group (Beaumont, 1994). Nonetheless, it remains possible that stochastic influences (genetic drift) probably interact with one or more deterministic forces specific to these diagnostic loci to produce concordant clines for these markers and in dissociating the position and width of these clines from others (Barton, 1993).…”

Genotypes of Mytilus from waters of different salinity around Bergen, Norway

“…None of these explanations can fully explain the observations. Beaumont (1994) showed that PGM* and PGI* are not linked in M. edulis. Non-linkage of these two loci was also observed in mussels by Gardner et al (1996), and thus the two loci PGI* and PGM* make independent contributions to the identification of different groups of blue mussels.…”