Why isn’t diversity proportional to population size?

Natural selection via hitchhiking and background selection constrains neutral diversity, especially in species with larger census sizes.

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How do HH and BGS affect linked neutrals?

Both purge linked neutral mutations.

What pattern do larger-Nc species show?

Stronger correlation between neutral polymorphism and recombination rate.

What does that indicate about selection’s role?

Selection plays a disproportionately large role in large-Nc species’ polymorphism.

What classic observation motivates the work?

Neutral diversity ranges less than census size ranges (Lewontin’s paradox).

Why does recombination matter here?

It modulates how strongly selection affects linked neutral sites.

What confounder do authors flag?

Cryptic population structure.

What genomic scale is affected?

Patterns of neutral genetic variation at linked sites across the genome.

What is genetic hitchhiking?

Positive selection sweeping linked neutral mutations.

What is background selection?

Negative selection removing linked neutrals.

Best undergraduate takeaway?

Selection on linked sites can erase the simple Ne–diversity expectation.