Genetic diversity of European populations of the invasive soft-shell clam Mya arenaria (Bivalvia)

Abstract

The genetic diversity of the soft-shell clam Mya arenaria from seven locations in Europe (two stations in the southern Baltic Sea (the Gulf of Gdansk) and two in the North Sea (Veerse Meer and Oosterschelde), and three additional stations in the Denmark Straits and Bay of Biscay) was determined using starch gel electrophoresis of allozymes. The results showed a low level of genetic variability and a lack of genetic di¡erentation among the populations studied. Basic polymorphism characteristics calculated for populations from the North Sea estuaries and the Gulf of Gdansk were: He 0.094^0.145, Ho 0.092^0.130, percentage of polymorphic loci 33 (0.95 criterion), mean number of alleles per locus 2.0^2.7. The mean value of F ST was 0.0133 and not signi¢cant. It is concluded that in spite of a low level of genetic polymorphism the soft-shell clam is a successful colonizer. The genetic homogeneity among the populations re£ects rapid population extension, alleles neutrality and a high gene £ow.

Metapopulation dynamics of the softshell clam, Mya arenaria

“…The low genetic diversity and minimal genetic structure observed in COI combined with previous results showing limited genetic diversity in Mya arenaria using nuclear sequences (Caporale et al, 1997) and allozymes (Morgan et al, 1978;Lasota et al, 2004) suggests that the brood stock origins may not be critical to maintaining levels of genetic diversity and patterns of genetic structure across the NWA. Results of this study suggest that brood stocks should be quite similar regardless of their locality, and their resulting juvenile seed clams are likely interchangeable across geography.…”

“…Caporale et al (1997) found similar low variability in three regions of the NWA (12 locations total) using the internal transcribed spacer ribosomal DNA region (nDNA), and concluded that although the three regions were not genetically distinct, the data from the study were insufficient to indicate a panmictic population. More recently, Lasota et al (2004) used allozymes to study seven locations in the northeast Atlantic and two in the North Sea. They also found low genetic variability and a lack of genetic differentiation, and concluded that M. arenaria is a successful invader despite a high degree of genetic homogeneity.…”

“…One process that could contribute to limited genetic structure across the NWA is a recent population expansion event, also suggested by Lasota et al (2004). The NWA was heavily impacted by ice sheets during the Pleistocene glacial period approximately 2.5 million years ago, with the southern limit of glaciation near Cape Cod, Massachusetts (Shackleton et al, 1984;Cronin, 1988).…”

Comparative study of ecophysiological and biochemical variation between the Baltic and North Sea populations of the invasive soft shell clam Mya arenaria (L. 1758)

“…The aim of the present study was to determine differences in the ecophysiological traits and biochemical composition between two populations of Mya arenaria living in the Baltic and North Sea, and to identify links between those differences and local environmental conditions with special emphasis on salinity and temperature. The populations analyzed in the present study were previously subject to genetic analysis, which showed no significant geographical genetic differentiation of isoenzymes and COI mtDNA gene sequences (Lasota et al 2004;Lasota et al -in preparation).…”

“…Genetic studies on the softshell clam Mya arenaria based on protein-coding markers, i.e. allozymes and mtDNA, showed a relatively low level of genetic polymorphism and a weak genetic structure on a large geographical scale as compared to other marine eurytopic invertebrates (Lasota et al 2004, Strasser & Barber 2009). Thus, adaptation to environmental heterogeneity in the soft-shell clam may occur through physiological acclimatization.…”