MITOCHONDRIAL-DNA VARIATION IN THE SCALLOP PECTEN-MAXIMUS (L) ASSESSED BY A PCR-RFLP METHOD

Two PCR-RFLP mitochondrial DNA (mtDNA) markers were developed through the cloning and sequencing of mtDNA from the scallop Pecten maximus, a nd were used to study genetic differentiation of UK and Atlantic coast populations of this species. Although no distinct pattern of mtDNA ha plotype frequencies was apparent and no diagnostic haplotypes were ide ntified for any population, sequence divergence data provided convinci ng evidence that a P. maximus sample taken from Mulroy Bay, fire, a se mi-enclosed sea lough, was differentiated from ail other samples. Howe ver, this could not be unequivocally attributed to a restriction in ge ne flow, as the sample consisted of an ongrown single spatfall, which may not have been representative of the wild population. Despite the i nability to separate populations on the basis of haplotype frequency, it was noteworthy that the frequency pattern of the commonest haplotyp e varied between sampling sites in a manner similar to that of allozym e allele frequencies in Aequipecten opercularis, a scallop species wit h a similar distribution and life history: for which there is evidence of population subdivision. Pecten maximus from St Brieuc Bay, reasone d to be a self-recruiting population from reproductive and physiologic al evidence, could not be separated from other populations using mtDNA markers. Further investigation of this population with alternative ma rkers is warranted.