TANDEM REPEAT POLYMORPHISM AND HETEROPLASMY IN THE MITOCHONDRIAL CONTROL REGION OF REDFISHES (SEBASTES, SCORPAENIDAE)

Three species of redfish (Sebastes) share a common pattern of mitochon drial DNA tandem repeat polymorphism and heteroplasmy in the northwest Atlantic Ocean. All three species exhibit 9-17 copies of an approxima tely 275 base pair (bp) tandem repeat situated within the 3' domain of the control region. Sequence analysis of cloned mtDNA from S. mentell a revealed that the tandem array is adjacent to the tRNA(phe) gene, an d that the repeat shares 53% identity with the tRNA(phe) gene and part of the 12S rRNA gene. These features, as well as potential secondary structure assumed by the repeat, are consistent with previously propos ed models explaining tandem duplications in the 3' end of the control region. In a sample comprising 36 S. fasciatus, 52 S. mentella, and 13 S. marinus taken near Newfoundland, neither the mean number of repeat s per fish (12.2-12.7) nor the frequency of heteroplasmy varied signif icantly among species. A total of 42% of the redfishes were heteroplas mic, bearing either two or three repeat variants (33% and 9%, respecti vely). The similarity of the frequency distributions of tandem repeat variants in the three species suggests either a common balance between mutation and selection in the three species, or mitochondrial gene fl ow between them.