Meeting Abstract
Eukaryotic biology is genetically encoded by a nuclear genome and one or many cytoplasmic genomes. The division of labor between these organelles requires their functional and evolutionary integration and has important implications in evolution, conservation, and medicine. The mitochondrial genome is especially prone to accumulating deleterious mutations which may disrupt mitonuclear integration thus favoring the recurrent evolution of nuclear restorers of mitochondrial function. In addition, uniparental inheritance may contribute to an ‘asymmetric sieve’ resulting in sex-specific fitness effects especially in hybrids. Mitonuclear conflicts may therefore be an important driver of postzygotic isolation between diverging populations. Here, we present recent work on the genomic signatures of mitonuclear coevolution across eight populations of the copepod Tigriopus californicus and investigate the possibility of sex-specific genetic architecture for postzygotic isolation. Populations of T. californicus show extreme mitochondrial DNA (mtDNA) divergence, with an average of 19.6% nucleotide divergence across the genome, as well as high levels of amino acid differentiation. Nuclear encoded genes predicted to interact with mtDNA and products show elevated rates of protein evolution, indicating compensatory nuclear evolution. In fourth generation recombinant inbred lines between populations, hybrid incompatibility is distributed widely throughout the genome with males suffering almost ten times the amount of hybrid incompatibility than females. Together, these results reveal the potential importance of mitonuclear coevolution as a driver of population differentiation and the evolution of hybrid incompatibility as well as the presence of sex-specific genetic architecture of hybrid incompatibility in T. californicus.
