Genetic differentiation of the Iceland scallop Chlamys islandica (Pectinidae) in the northern Atlantic Ocean

Abstract

Allozymic variation at gene loci encoding for glucosephosphate isomerase, phosphoglucomutase and superoxide dismutase was investigated In populations of Chlarnys islandica from waters around Jan Mayen, Spitsbergen, Bear Island and northern Norway. The Gpi locus was particularly polymorphic with at least 12 different alleles and a mean heterozygosity of 84 % Half the individuals were heterozygous at Pgm-2 and between 30 and 40 % at Sod. The high polymorphism at Gpi runs counter to an earlier hypothesis suggesting a positive correlation between environmental variability and Gpi polymorphism of pectinids. Pgm-2 and Sod revealed significant allele frequency heterogeneity among the different areas, Gpi only when the effective number of alleles was considered. The species has a large dispersal potential during a long planktonic larval stage, but information on the surface current system in the North Atlant~c suggests that restr~cted gene flow, with possible contributions from selective constraints, account for the observed pattern in gene variability. It is suggested that the conservative approach of managing each area as if it contained discrete genetic units of the species should be adopted.