MITOCHONDRIAL-DNA FROM THE SCALLOP PECTEN-MAXIMUS - AN UNUSUAL POLYMORPHISM DETECTED BY RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM ANALYSIS

We present an analysis of mitochondrial DNA diversity within the scall op Pecten maximus. Twenty-seven individuals of Pecten maximus were sam pled from three populations from the west coast of Brittany (France) a nd their mtDNA assayed for restriction site polymorphism. Thirty-four variable and conserved cleavage sites have been mapped. They occur in the coding region as well as in the noncoding one, which has also prev iously been shown to be variable in length. Nucleotide divergence betw een two P. maximus mtDNA types can reach 3.4 per cent and the nucleoti de diversity is 1 per cent. Data using seven restriction endonucleases clearly distinguished 27 genotypes; each individual possessed a uniqu e mitochondrial genotype. Phylogenies derived from mtDNA restriction a nalysis are not concordant with data on reproductive behaviour or ecol ogical studies. The three populations sampled present similar distribu tions of the different mitochondrial genotypes, although the scallop s tock of the Bay of Saint Brieuc is considered, from physiological para meters, to be genetically distinct from all other populations. Therefo re, we suggest that P. maximus should fall into category IV of phyloge ographical pattern, i.e. continuous mtDNA genotypes with a high gene f low.