Biochemical and evolutionary interactions between mitochondrial and nuclear genomes (βmitonuclear interactionsβ) are proposed to underpin fundamental aspects of biology including evolution of sexual reproduction, adaptation and speciation. We investigated the role of pre-mating isolation in maintaining functional mitonuclear interactions in wild populations bearing diverged, putatively co-adapted mitonuclear genotypes. Two lineages of eastern yellow robin Eopsaltria australis-putativelyβ¦ β¦