Introgression of non-native mitochondrial haplotypes from farmed to wild Atlantic salmon

Farmed salmon escape and interbreed with wild Atlantic salmon on a large scale. We studied introgression of mitochon-drial haplotypes from farmed Atlantic salmon originating from the Eastern Atlantic phylogenetic group to wild salmon of the Barents-White Sea (BWS) phylogenetic group. We find that farmed genetic introgression introduced novel, non-native hap-lotypes into the BWS phylogenetic group. The mitochondrial genome has important functional effects and is inherited as a haploid from the mother. Hence, the observed introgression across natural genetic barriers is expected to cause long-lasting functional maladaptation of the hybrids in the maternal line. As the use of farmed Atlantic salmon from non-native phyloge-netic groups is widespread in aquaculture, the impact on wild Atlantic salmon may be more severe than previously recognized. Our results highlight the ecological risks of releasing non-native wild and domesticated animals.

Automated summary

Farm-raised Atlantic salmon escape and mate with wild ones, introducing non-native mitochondrial haplotypes to the wild population. This genetic introgression can cause long-lasting functional maladaptation in the hybrids due to the important role of mitochondrial genome and maternal inheritance. The widespread use of farm-raised salmon from non-native groups in aquaculture poses greater ecological risks to wild salmon than previously recognized.