Natural selection
Why do immune genes keep evolving across tetrapods?
Open access · cc by · source: Europe PMC
Shared positive selection in birds and mammals concentrates on immune—especially antiviral—genes, implicating pathogens as a consistent selective pressure.
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
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
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.
Methodology
Authors scanned orthologous genes across birds (and compared to mammals) for positive selection, then linked selected genes to pathogen-responsive transcriptomes.
Limitations
Shared selection could reflect convergence or ancient shared pressure; finer tetrapod clades still need scanning.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Positive-selection scans across bird orthologs, compared with mammals, found immune pathways as recurrent targets. Genes selected in birds were enriched for selection in mammals, especially viral-response genes, and about 14% of genes were selected in all tests. Shared selection could still be convergence rather than one continuous pressure.
Evidence for the claim as stated.
These papers do not build the same kind of tree. HSP90 and MYB papers classify gene families; the immune-gene paper scans orthologs for repeated positive selection (~14% selected in all tests); Aspergillus and Listeria papers mix clade phylogeny with pan-genome gene content; turtle and Medicago papers are organismal genomes whose phylogeny is background for physiology or breeding. A student who treats every 'phylogenetic analysis' hit as a species tree will misread the result.
Evidence for the claim as stated.
What 'accessory' or 'lineage-specific' genes imply is itself unsettled. Listeria accessory genes concentrate in hotspots with mobile elements and aid diagnostics, but presence/absence does not prove each virulence phenotype. Aspergillus section Nigri's ~1,800 unique genes are not experimentally validated one by one. Immune-gene sharing of selection between birds and mammals can be convergence or ancient pressure.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
These papers do not build the same kind of tree. HSP90 and MYB papers classify gene families; the immune-gene paper scans orthologs for repeated positive selection (~14% selected in all tests); Aspergillus and Listeria papers mix clade phylogeny with pan-genome gene content; turtle and Medicago papers are organismal genomes whose phylogeny is background for physiology or breeding. A student who treats every 'phylogenetic analysis' hit as a species tree will misread the result.
- Supports · HSP90 family across kingdoms
- Supports · MYB transcription-factor families in plants
- Supports · How open is the Listeria pan-genome?
What 'accessory' or 'lineage-specific' genes imply is itself unsettled. Listeria accessory genes concentrate in hotspots with mobile elements and aid diagnostics, but presence/absence does not prove each virulence phenotype. Aspergillus section Nigri's ~1,800 unique genes are not experimentally validated one by one. Immune-gene sharing of selection between birds and mammals can be convergence or ancient pressure.
- Supports · How open is the Listeria pan-genome?
- Supports · Aspergillus genomic diversity
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