Diversifying selection between populations that inhabit different environments can promote lineage divergence within species and drive speciation. The mitochondrial genome and nuclear genes with mitochondrial function can be a target for climate-driven selection because they co-encode essential proteins of the oxidative phosphorylation system or regulate system functioning. Understanding evolutionary drivers in wild systems requires integration of comparative and population genomics and studies of physiology and fitness. Multi-species investigation into intraspecific mitochondrial variation showed that in half of the widespread Australian songbirds climate significantly predicts distribution of mitochondrial variation beyond that predicted by geographic distances and geographic position. Analyses of mitogenomes yielded candidates for positive selection in some lineages of some species. In one of these, the Eastern Yellow Robin, north-south lineage divergence ~2 million years ago was followed by two adaptive mitochondrial introgressions. Now, inland and coastal populations occupy areas with different climates and harbour divergent mitolineages despite similarity for majority of nuclear genes. But these populations are differentiated at a small subset of nuclear genes that map to a ~15 megabase region on autosome 1A. This region is characterised by strong linkage disequilibrium and low genetic diversity and is enriched by genes with roles linked to mitochondrial functions (N-mt genes). Elevated differentiation and sequence divergence at this region suggest that N-mt genes might act as barrier loci resisting gene flow. Similar regions of differentiation on chromosome 1A are found among other songbirds, and may present a common mechanism facilitating climate adaptation. We are testing whether the two genomic forms of Eastern Yellow Robin are adapted to their local environments via traits connected with mitochondrial metabolism.
Diversifying selection between populations that inhabit different environments can promote lineage divergence within species and drive speciation. The mitochondrial genome and nuclear genes with mitochondrial function can be a target for climate-driven selection because they co-encode essential proteins of the oxidative phosphorylation system or regulate system functioning. Understanding evolutionary drivers in wild systems requires integration of comparative and population genomics and studies of physiology and fitness. Multi-species investigation into intraspecific mitochondrial variation showed that in half of the widespread Australian songbirds climate significantly predicts distribution of mitochondrial variation beyond that predicted by geographic distances and geographic position. Analyses of mitogenomes yielded candidates for positive selection in some lineages of some species. In one of these, the Eastern Yellow Robin, north-south lineage divergence ~2 million years ago was followed by two adaptive mitochondrial introgressions. Now, inland and coastal populations occupy areas with different climates and harbour divergent mitolineages despite similarity for majority of nuclear genes. But these populations are differentiated at a small subset of nuclear genes that map to a ~15 megabase region on autosome 1A. This region is characterised by strong linkage disequilibrium and low genetic diversity and is enriched by genes with roles linked to mitochondrial functions (N-mt genes). Elevated differentiation and sequence divergence at this region suggest that N-mt genes might act as barrier loci resisting gene flow. Similar regions of differentiation on chromosome 1A are found among other songbirds, and may present a common mechanism facilitating climate adaptation. ...
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