Detecting adaptive evolution based on association with ecological gradients: orientation matters!

Area of Science:

• Population Genetics
• Evolutionary Biology
• Genomics

Background:

• Identifying local adaptation relies on correlating allele frequencies with ecological variables.
• Geographic variation at neutral loci can confound these ecological associations.

Purpose of the Study:

• To investigate how the orientation of ecological gradients impacts the detection of local adaptation during spatial expansion.
• To assess the influence of range expansion dynamics on genomic association methods.

Main Methods:

• Utilized range expansion simulations to model population genetic scenarios.
• Tested three ecological association methods under varying gradient orientations.
• Analyzed the impact of gradient alignment relative to the expansion axis on false-positive rates.

Main Results:

• Counter-intuitively, fewer false-positive associations were detected when ecological gradients aligned with the main axis of expansion.
• The orientation of ecological gradients significantly affects the reliability of adaptation detection methods.
• This effect was consistent across the three tested ecological association methods.

Conclusions:

• The alignment of ecological gradients with range expansion axes can improve the accuracy of detecting local adaptation.
• Findings have significant implications for analyzing genomic data in non-equilibrium populations, especially during climate change-induced range shifts.
• Future studies should consider spatial expansion dynamics and gradient orientation in adaptation genomics.