Demographic Processes Linked to Genetic Diversity and Positive Selection across a Species' Range

Area of Science:

• Population genomics
• Evolutionary biology
• Plant genetics

Background:

• Demographic processes shape genetic variation and selection efficacy.
• Understanding local and species-range demographic influences on genomic diversity is crucial.

Purpose of the Study:

• To disentangle local (mating system, census size) and range-scale (glacial history, admixture) demographic impacts on genomic diversity and selection signatures in North American *Arabidopsis lyrata*.
• To quantify the relative importance of these demographic factors in driving genomic variation.

Main Methods:

• Re-sequencing data from 52 *Arabidopsis lyrata* populations across its North American range.
• Analysis of within-population genomic diversity and genomic signatures of positive selection.
• Statistical modeling to assess the influence of demographic variables.

Main Results:

• Mating system and post-glacial recolonization explained ~60% of genomic diversity variation and ~52% of positive selection signature variation.
• Selfing populations and those with longer postglacial expansion routes showed lower diversity and reduced positive selection.
• Admixture also correlated with reduced signatures of positive selection.

Conclusions:

• Recent range expansion significantly influences genomic diversity (coding and non-coding DNA), rivaling the effect of selfing.
• Reduced effective population size and compromised selection in recently colonized areas may limit species distribution.