Broken barriers: the impact of mitochondrial introgression on the life-history and behaviour of threatened Atlantic salmon

The viability of wild populations is increasingly threatened by human-mediated gene flow between previously isolated groups.

One crucial, but overlooked, consequence of human-mediated gene flow is the introduction of non-native mitochondrial DNA (mtDNA) into local populations. Genes encoded by mtDNA are responsible for energy production and are thus crucial to the key processes of life.

Energy production is also dependent on the nuclear genome, resulting in the coevolution of the mitochondrial and nuclear genomes.

Indeed, introgression of non-native mtDNA can result in incompatibilities between mitochondrial and nuclear genotypes that decrease species performance.

Recent evidence has documented genetic introgression from farmed Atlantic salmon into Norwegian and Swedish populations, with evidence that this is reducing fitness in wild fish. But how mtDNA introgression and mito-nuclear incompatibilities influence wild salmon is not known.

Given that Atlantic salmon are a species of high conservation importance, we urgently need to understand how mtDNA introgression affects the status of wild salmon.

My project will address this key knowledge gap by investigating how mitochondrial introgression from farmed fish affects the reproduction, life-history, and behaviour of wild Atlantic salmon populations.

The proposed project is set to significantly advance how we evaluate the risks posed by human-mediated gene flow and strengthen our capacity to conserve European salmon populations.