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Introgression drives repeated evolution of winter coat color polymorphism in hares
Iwona Giska1, Liliana Farelo1, João Pimenta1
1CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos (CIBIO), Rede de Investigação em Biodiversidade e Biologia Evolutiva (InBIO), Universidade do Porto, 4485-661 Vairão, Portugal.
Summary
Seasonal coat color change in mountain hares evolved through introgression, with the Agouti gene
Area of Science:
- Evolutionary biology
- Genetics
- Animal coloration
Background:
- Seasonal coat color change is a critical adaptation for camouflage in snowy environments, observed across numerous mammal and bird species.
- Some species exhibit nonwhite winter morphs, suggesting independent evolution of local adaptations to reduced snowfall.
- The introduction of Scandinavian mountain hares to the Faroe Islands provides a unique model for studying seasonal coat color polymorphism.
Purpose of the Study:
- To investigate the genetic basis and evolutionary mechanisms behind the shift to a winter-gray coat color in Faroese mountain hares.
- To identify the specific genes and genomic regions responsible for seasonal coat color variation.
- To understand the role of introgression and selection in the evolution of coat color traits.
Main Methods:
- Whole-genome scans for genetic differentiation between populations.
- Single-nucleotide polymorphism (SNP) genotyping to pinpoint associated genomic regions.
- Gene expression analysis of the Agouti gene in skin tissue during molting.
- Comparative whole-genome analyses across multiple hare species.
Main Results:
- The winter coat color polymorphism in Faroese hares is strongly associated with the Agouti gene region.
- Lower Agouti gene expression in winter-gray hares suggests regulatory changes influence coat color.
- Genomic signatures indicate a selective sweep, with positive selection driving the fixation of the gray variant.
- The winter-gray variant in hares originated via introgression from a non-color-changing species.
Conclusions:
- The Agouti gene's regulatory region plays a recurrent role in modulating seasonal coat color change across different species.
- Introgression is a significant evolutionary force in generating coat color diversity, particularly in response to environmental factors like snow cover.
- The Faroese mountain hare population serves as a valuable model for understanding rapid adaptation and the evolution of phenotypic plasticity.
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