Mitochondrial DNA sequence variation and phylogenetic relationships among Michigan brown trout (Salmo trutta) strains

Despite the extensive use of mitochondrial DNA (mtDNA) in studies of European brown trout (Salmo trutta) populations, little information is available regarding the genetic composition or phylogenetic relationships among strains of Michigan brown trout. The objective of this study was to quantify the amount of polymorphism among three strains of Michigan brown trout at the mtDNA level and to infer genetic relatedness among representative individuals of these strains. This was accomplished by sequencing the ND1 region of mtDNA and constructing phylogenetic trees based on detected sequence variation. A total of 23 single nucleotide polymorphisms (SNPs) were found in the ND1 region with two additional SNPs found in the 16S rRNA region directly preceding ND1. All but two fish examined displayed synonymous substitutions at all 23 ND1 SNP sites. Two fish belonging to a mtDNA haplotype found in the Seeforellen strain showed nonsynonymous substitutions at two of the sites. Further study would be necessary to determine if these amino acid substitutions have any functional significance.