Data from: Mitonuclear interactions impact aerobic metabolism in hybrids and may explain mitonuclear discordance in young, naturally hybridizing bird lineages

Understanding genetic incompatibilities and genetic introgression between
incipient species are major goals in evolutionary biology. Mitochondrial
genes evolve rapidly and exist in dense gene networks with coevolved
nuclear genes, suggesting that mitochondrial respiration may be
particularly susceptible to disruption in hybrid organisms. Mitonuclear
interactions have been demonstrated to contribute to hybrid dysfunction
between deeply divergent taxa crossed in the laboratory, but there are few
empirical examples of mitonuclear interactions between younger lineages
that naturally hybridise. Here we use controlled hybrid crosses and high
resolution respirometry to provide the first experimental evidence in a
bird that inter-lineage mitonuclear interactions impact mitochondrial
aerobic metabolism. Specifically, respiration capacity of the two
mitodiscordant backcrosses (with mismatched mito-nuclear combinations)
differ from one another, although they do not differ significantly from
the parental groups or mitoconcordant backcrosses as we would expect of
mitonuclear disruptions. In the wild hybrid zone between these subspecies
the mitochondrial cline centre is shifted west of the nuclear cline
centre, which is consistent with the direction of our experimental
results. Our results therefore demonstrate asymmetric mitonuclear
interactions that impact the capacity of cellular mitochondrial
respiration and may help to explain the geographic discordance between
mitochondrial and nuclear genomes observed in the wild.