Positive and purifying selection in mitochondrial genomes of a bird with mitonuclear discordance

Hernan Morales, Alexandra Pavlova, Leo George Joseph, Paul Sunnucks

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Diversifying selection on metabolic pathways can reduce intraspecific gene flow and promote population divergence. An opportunity to explore this arises from mitonuclear discordance observed in an Australian bird Eopsaltria australis. Across >1500 km, nuclear differentiation is low and latitudinally structured by isolation by distance, whereas two highly divergent, parapatric mitochondrial lineages (>6.6 in ND2) show a discordant longitudinal geographic pattern and experience different climates. Vicariance, incomplete lineage sorting and sex-biased dispersal were shown earlier to be unlikely drivers of the mitonuclear discordance; instead, natural selection on a female-linked trait was the preferred hypothesis. Accordingly, here we tested for signals of positive, divergent selection on mitochondrial genes in E. australis. We used codon models and physicochemical profiles of amino acid replacements to analyse complete mitochondrial genomes of the two mitochondrial lineages in E. australis, its sister species Eopsaltria griseogularis, and outgroups. We found evidence of positive selection on at least five amino acids, encoded by genes of two oxidative phosphorylation pathway complexes NADH dehydrogenase (ND4 and ND4L) and cytochrome bc1 (cyt-b) against a background of widespread purifying selection on all mitochondrial genes. Three of these amino acid replacements were fixed in ND4 of the geographically most widespread E. australis lineage. The other two replacements were fixed in ND4L and cyt-b of the geographically more restricted E. australis lineage. We discuss whether this selection may reflect local environmental adaptation, a by-product of other selective processes, or genetic incompatibilities, and propose how these hypotheses can be tested in future.
Original languageEnglish
Pages (from-to)2820 - 2837
Number of pages18
JournalMolecular Ecology
Volume24
Issue number11
DOIs
Publication statusPublished - 2015

Cite this

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title = "Positive and purifying selection in mitochondrial genomes of a bird with mitonuclear discordance",
abstract = "Diversifying selection on metabolic pathways can reduce intraspecific gene flow and promote population divergence. An opportunity to explore this arises from mitonuclear discordance observed in an Australian bird Eopsaltria australis. Across >1500 km, nuclear differentiation is low and latitudinally structured by isolation by distance, whereas two highly divergent, parapatric mitochondrial lineages (>6.6 in ND2) show a discordant longitudinal geographic pattern and experience different climates. Vicariance, incomplete lineage sorting and sex-biased dispersal were shown earlier to be unlikely drivers of the mitonuclear discordance; instead, natural selection on a female-linked trait was the preferred hypothesis. Accordingly, here we tested for signals of positive, divergent selection on mitochondrial genes in E. australis. We used codon models and physicochemical profiles of amino acid replacements to analyse complete mitochondrial genomes of the two mitochondrial lineages in E. australis, its sister species Eopsaltria griseogularis, and outgroups. We found evidence of positive selection on at least five amino acids, encoded by genes of two oxidative phosphorylation pathway complexes NADH dehydrogenase (ND4 and ND4L) and cytochrome bc1 (cyt-b) against a background of widespread purifying selection on all mitochondrial genes. Three of these amino acid replacements were fixed in ND4 of the geographically most widespread E. australis lineage. The other two replacements were fixed in ND4L and cyt-b of the geographically more restricted E. australis lineage. We discuss whether this selection may reflect local environmental adaptation, a by-product of other selective processes, or genetic incompatibilities, and propose how these hypotheses can be tested in future.",
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Positive and purifying selection in mitochondrial genomes of a bird with mitonuclear discordance. / Morales, Hernan; Pavlova, Alexandra; Joseph, Leo George; Sunnucks, Paul.

In: Molecular Ecology, Vol. 24, No. 11, 2015, p. 2820 - 2837.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Positive and purifying selection in mitochondrial genomes of a bird with mitonuclear discordance

AU - Morales, Hernan

AU - Pavlova, Alexandra

AU - Joseph, Leo George

AU - Sunnucks, Paul

PY - 2015

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