Why do immune genes keep evolving across tetrapods?
Shared positive selection in birds and mammals concentrates on immune—especially antiviral—genes, implicating pathogens as a consistent selective pressure.
Source
Immune genes are hotspots of shared positive selection across birds and mammals
Study at a glance
- Design
- Computational / modelling — Positive-selection scans of avian orthologs with comparison to mammalian selection patterns
- N
- N=39 · 39 bird species; up to 11,231 genes analysed (gene-tree models)
- Population
- Bird genomes (compared with mammal orthologs)
- Outcome
- Shared positive selection on immune genes across birds and mammals
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Inspect source passages
Why do immune genes keep evolving across tetrapods?
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14% of analyzed genes under positive selection in all tests.
In total, 14% of analyzed genes are found to be under positive selection in all tests (, Table 2 (raw gene tree results), Table 3 (raw species tree results)).
What do shared positive-selection signatures match?
shared signatures of positive selection are consistent with pathogen-mediated selection.
What they did
Authors scanned orthologous genes across birds (and compared to mammals) for positive selection, then linked selected genes to pathogen-responsive transcriptomes.
What they found
Immune pathways are recurrent selection targets; genes selected in birds are enriched for selection in mammals, especially viral-response genes. About 14% of genes are selected in all tests.
The limits
What it doesn't show
Shared selection could reflect convergence or ancient shared pressure; finer tetrapod clades still need scanning.
Key terms
- Positive selection
- Natural selection favoring amino-acid changes.
- Orthologues
- Genes in different species descended from a common ancestor.
- Pathogen-mediated selection
- Host evolution driven by infectious agents.
- Immune hotspots
- Gene classes repeatedly targeted by selection across taxa.
- Viral response genes
- Host genes induced by or interacting with viruses.
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Most consistent selective pressure claimed:
Common questions
What selective pressure looks most consistent?
Pathogens, especially viruses.
Do bird-selected genes matter in mammals?
Yes—they are more likely selected and immune/viral enriched.
How often are genes selected in all tests?
About 14%.
Do transcriptomes support this?
Pathogen-upregulated genes are enriched for selection.
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