Globally Relaxed Selection and Local Adaptation in Boechera stricta

Area of Science:

• Evolutionary biology
• Population genetics
• Genomics

Background:

• The efficacy of natural selection varies across populations and genomes, but its underlying causes are not fully understood.
• Understanding selection efficacy is crucial for explaining patterns of genetic variation and local adaptation.

Purpose of the Study:

• To quantify selection strength and characterize local adaptation in Boechera stricta using whole-genome data.
• To investigate the influence of effective population size, nucleotide composition, and recombination rate on selection efficacy.

Main Methods:

• Whole-genome sequencing of 467 Boechera stricta accessions.
• Analysis of genetic diversity, distribution of fitness effects, and rates of adaptive evolution.
• Comparison of selection patterns across four distinct population groups (NOR, WES, UTA, COL).

Main Results:

• Low genetic diversity observed at functional constraint sites, indicating purifying selection.
• Evidence for relaxed negative and positive selection, with smaller effective population sizes (Ne) correlating with reduced selection efficacy.
• GC-biased gene conversion and recombination rates showed varied impacts on selection efficacy across different populations.

Conclusions:

• Effective population size, nucleotide composition, and recombination rate are key determinants of selection efficacy.
• Differential adaptation observed among Boechera stricta groups, influenced by varying genomic and demographic factors.
• This study enhances understanding of how natural selection and local adaptation shape genomic variation in plants.