Perpendicular axes of differentiation generated by mitochondrial introgression

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Differential introgression of mitochondrial vs. nuclear DNA generates discordant pat- terns of geographic variation and can promote population divergence and speciation. We examined a potential case of mitochondrial introgression leading to two perpendic- ular axes of differentiation. The Eastern Yellow Robin Eopsaltria australis, a wide- spread Australian bird, shows a deep mitochondrial split that is perpendicular to north–south nuclear DNA and plumage colour differentiation. We propose a scenario to explain this pattern: (i) first, both nuclear and mitochondrial genomes differentiated in concert during north–south population divergence; (ii) later, their histories discon- nected after two mitochondrial introgression events resulting in a deep mitochondrial split perpendicular to the nuclear DNA structure. We explored this scenario by coales- cent modelling of ten mitochondrial genes and 400 nuclear DNA loci. Initial mitochon- drial and nuclear genome divergences were estimated to have occurred in the early Pleistocene, consistent with the proposed scenario. Subsequent climatic transitions may have driven later mitochondrial introgression. We consider neutral introgression unlikely and instead propose that the evidence is more consistent with adaptive mito- chondrial introgression and selection against incompatible mitochondrial-nuclear com- binations. This likely generated an axis of coastal-inland mitochondrial differentiation in the face of nuclear gene flow, perpendicular to the initial north–south axis of differentiation (reflected in genomewide nuclear DNA and colour variation).
Original languageUndefined/Unknown
JournalMolecular Ecology
Publication statusPublished - 2017
Externally publishedYes

ID: 246096240