Ancestry-specific recent effective population size in the Americas

Area of Science:

• Population genetics
• Human population history
• Genomic studies

Background:

• Population size dynamics are influenced by growth, migration, and disease.
• Historical population size impacts genetic association study power.
• Admixed populations require analysis of both overall and ancestral effective sizes.

Purpose of the Study:

• To estimate historical effective population sizes for admixed American populations.
• To investigate ancestry-specific effective population sizes.
• To understand population dynamics, including bottlenecks, over the past hundred generations.

Main Methods:

• Utilized identity by descent (IBD) and local ancestry inference.
• Analyzed genome-wide genetic data from nine Hispanic/Latino populations and US African-American and European-American populations.
• Estimated overall and ancestry-specific effective population sizes.

Main Results:

• Pre-admixture effective sizes of ancestral populations varied across sampled groups.
• Overall effective population sizes decreased significantly post-immigration, reaching a minimum ~12 generations ago.
• Population bottlenecks were observed, with Puerto Rican populations showing the smallest (1,000) and Pittsburgh African-Americans the largest (200,000).

Conclusions:

• Ancestral populations for admixed groups originated from distinct subpopulations.
• Significant population size fluctuations occurred following European and African admixture.
• Effective population size dynamics reveal unique demographic histories for different admixed groups.