Evolution of mitochondrial DNA in the genus Salmo

The mitochondrial genome (mtDNA) is a valuable source of data for evolutionary studies because of its small size, lack of recombination and its higher rate of accepted mutations than nuclear coding sequences. All salmonid rnitochondrial genomes are -16.7 Kb in size and identical in their genome organization. PCR amplification with thirty-three conserved primer pairs and subsequent direct sequencing was used to obtain whole mitochondrial genome sequences from fourteen Atlantic salmon (Salmo snlar) samples. The nucleotide and amino acid sequences were aligned and compared with those of a sister species, brown trout (Salmo trutta) to study the mode and tempo of mtDNA evolution. Varying percent sequence divergence was observed in different parts of the genome suggesting that different constraints operate across the genome. Further, by measuring the amount of variation in the Atlantic salmon from different geographical locations, previous hypotheses regarding the structuring of Atlantic salmon populations were confirmed.