Artificial Selection Response due to Polygenic Adaptation from a Multilocus, Multiallelic Genetic Architecture

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Evolutionary Biology

Background:

• Adaptation to environmental changes relies on polygenic traits.
• Artificial selection experiments offer insights into complex genetic adaptations.
• Virginia chicken lines exhibit significant body weight divergence after 40 generations of selection.

Purpose of the Study:

• To dissect the genetic mechanisms underlying long-term polygenic adaptation in Virginia chicken lines.
• To identify quantitative trait loci (QTL) influencing body weight in selected chicken populations.
• To understand the range of genetic architectures involved in artificial selection responses.

Main Methods:

• Divergent selection for 56-day body weight over 40 generations.
• Intercrossing divergent lines and analyzing the F15 generation.
• Fine-mapping of major quantitative trait loci (QTL).

Main Results:

• Twenty loci explained over 60% of the additive genetic variance for body weight.
• Seven major QTL were identified and fine-mapped.
• Only two QTL mapped to single loci; others involved linked loci, multiple alleles, or epistasis.

Conclusions:

• The genetic architecture of polygenic traits can be diverse, involving single loci, linked loci, multiple alleles, and epistasis.
• Polygenic adaptation in the Virginia chicken lines demonstrates a broad spectrum of genetic mechanisms.
• Complex genetic adaptations can occur even in small populations with limited founder genetic diversity.