The genetic differentiation at quantitative trait loci under local adaptation

Area of Science:

• Evolutionary genetics
• Quantitative genetics
• Population genetics

Background:

• Adaptive traits are typically controlled by numerous genes, making them targets of natural selection.
• Detecting loci involved in local adaptation often relies on outlier values of allelic differentiation (FST).
• The classical 'selective sweep' paradigm may be insufficient for polygenic adaptation.

Purpose of the Study:

• To review theoretical expectations for allelic differentiation at quantitative trait loci (FSTQ) in relation to neutral genetic differentiation (FST) and phenotypic differentiation (QST).
• To identify scenarios where outlier-based methods for detecting selected loci may be unreliable.
• To explore the implications of polygenic adaptation for inferring local adaptation.

Main Methods:

• Adopting a quantitative genetics framework to analyze theoretical expectations.
• Comparing theoretical predictions with existing literature data.
• Reviewing recent methodological improvements for detecting selected loci.

Main Results:

• Outlier-based FST methods can be unreliable when neutral differentiation is high or when adaptation occurs through increased covariance of allelic effects rather than substantial allele frequency changes.
• Polygenic local adaptation with minor allele frequency shifts is likely in species like forest trees, especially for climate-related traits.
• High gene flow, numerous loci, and recent selection favor adaptation via allele covariation.

Conclusions:

• A quantitative genetics framework is more appropriate than the selective sweep paradigm for understanding polygenic adaptation.
• The effectiveness of FST outlier methods is limited in certain scenarios of local adaptation.
• Future research should consider polygenic adaptation and refine detection methods to better understand evolutionary processes.