Genetic comparison between sympatric anadromous steelhead and freshwater resident rainbow trout in British Columbia, Canada

Sympatrically occurring steelhead and rainbow trout ( n = 100) were collected from five river systems in British Columbia, Canada, and 1300 bp from the mitochondrial genome and 270 bp of the nuclear growth hormone 2 gene were sequenced to determine if the two forms are genetically differentiated. ND3 and D- loop sequence differences produced nine haplotypes while two length variants of the GH2 intron D were present. In one river system, steelhead and rainbow were genetically divergent based on mtDNA data but overall, no consistent genetic difference between life history types was found. Rather, genetic differences were associated with geography, suggesting that steelhead and rainbow trout are polyphyletic and the result of parallel evolution rather than members of two distinct lineages.