MITOCHONDRIAL-DNA RESTRICTION SITE VARIATION WITHIN AND AMONG 5 POPULATIONS OF ALASKAN COHO SALMON (ONCORHYNCHUS-KISUTCH)

Mitochondrial DNA (mtDNA) from three Gulf of Alaska and two Bering Sea populations of coho salmon (Oncorhynchus kisutch) was assayed with 21 restriction endonucleases. A restriction site map was constructed for 15 enzymes that recognized hexanucleotide sequences and aligned to th e rainbow trout (Oncorhynchus mykiss) gene map using the restriction m ap and known coho salmon sequences. The restriction site map and gene order of the coho salmon mtDNA genome are consistent with those of rai nbow trout. Variation was observed for six enzymes at 10 sites that re sulted in eight haplotypes. Variability and divergence observed exceed ed those previously observed for allozyme loci in coho salmon. When va riability that occurred only in single individuals was eliminated, two haplotypes that differed by four restriction sites remained. Variatio n at these sites was confirmed from polymerase chain reaction (PCR) am plified fragments. Bering Sea populations exhibited more variation tha n Gulf of Alaska populations. Explanations for the differences include more recent colonization by or smaller sizes of Gulf of Alaska popula tions.