An investigation of possible stock structure in Pecten maximus (L.) using multivariate morphometrics, allozyme electrophoresis and mitochondrial DNA polymerase chain reaction restriction fragment length polymorphism

Population heterogeneity in the scallop Pecten maximus (L.) has been studied by multivariate morphometrics and allozyme electrophoresis and compared with data from a mitochondrial DNA polymeruse chain reaction-restriction fragment length polymorphism method. Principal component analysis applied to shell measurements revealed some variation in shape, with significant differences in aspects of morphology detectable among populations. Trends suggestive of morphological distinctness of a population or populations were difficult to uncover; however, animals from Brest and La Trinite (Brittany, France) were consistently different from other P. maximus populations on the basis of principal component 1, largely attributable to hinge length. St. Brieuc Bay P. maximus, which are known to exhibit differences in reproductive cycle from neighboring populations and thus are thought to be reproductively isolated, could not be separated on the basis of shell shape, although limited differences in the number of ribs in comparison to other populations are evident. Allele frequencies at seven loci assessed by allozyme electrophoresis were essentially homogeneous throughout the sample range in accord with previous studies and provided little evidence for population subdivision, although allele frequencies at the Odh locus provided some evidence that two Scottish populations were genetically differentiated. This contrasted with both the morphological differences detected for two Brittany populations and with data from the mitochondrial DNA, which indicated that the P. maximus population from the semienclosed sea lough Mulroy Bay, Eire, was genetically differentiated from any other population sampled on the basis of sequence divergence values