Signatures of mito-nuclear climate adaptation in a warbler species complex

Of the few highly-differentiated nDNA regions between inland S. townsendi and S. occidentalis, two of these regions (on chromosome 5 and Z, respectively) are also differentiated between coastal and inland S. townsendi, similar to the mtDNA pattern. These two nDNA regions are associated with mitochondrial fatty acid metabolism. Moreover, these nDNA regions are correlated with mtDNA ancestries among sites, a pattern consistent with mito-nuclear co-adaptation.

Such mito-nuclear coevolution might be driven by climate-related selection, because the mito-nuclear ancestry is correlated with climatic conditions among sampling sites. These results suggest that cryptic differentiation in this species complex has been shaped by climate-correlated adaptation associated with mito-nuclear fatty acid metabolism.