Abstract
Populations change in size over time due to factors such as population growth, migration, bottleneck events, natural disasters, and disease. The historical effective size of a population affects the power and resolution of genetic association studies. For admixed populations, it is not only the overall effective population size that is of interest, but also the effective sizes of the component ancestral populations. We use identity by descent and local ancestry inferred from genome-wide genetic data to estimate overall and ancestry-specific effective population size during the past hundred generations for nine admixed American populations from the Hispanic Community Health Study/Study of Latinos, and for African-American and European-American populations from two US cities. In these populations, the estimated pre-admixture effective sizes of the ancestral populations vary by sampled population, suggesting that the ancestors of different sampled populations were drawn from different sub-populations. In addition, we estimate that overall effective population sizes dropped substantially in the generations immediately after the commencement of European and African immigration, reaching a minimum around 12 generations ago, but rebounded within a small number of generations afterwards. Of the populations that we considered, the population of individuals originating from Puerto Rico has the smallest bottleneck size of one thousand, while the Pittsburgh African-American population has the largest bottleneck size of two hundred thousand.
Highlights
Effective population size is a key factor in evolutionary genetic processes, such as drift and selection, which have important implications for medical genetics [1, 2]
Using genome-wide genetic data on several hundred individuals sampled from a population, we can estimate the current effective size of the population and the changes in effective size that have occurred over the past hundred generations
The following Institutes/Centers/ Offices contributed to the first phase of HCHS/SOL through a transfer of funds to the NHLBI: National Institute on Minority Health and Health Disparities, National Institute on Deafness and Other Communication Disorders, National Institute of Dental and Craniofacial Research (NIDCR), National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Neurological Disorders and Stroke, NIH Institution-Office of Dietary Supplements
Summary
Effective population size is a key factor in evolutionary genetic processes, such as drift and selection, which have important implications for medical genetics [1, 2]. During the last few generations, growth rates have slowed or become negative in many human populations due to the availability of effective birth control methods, higher levels of education for women, urbanization, and other factors [5]. In addition to these global trends, populations in the Americas have experienced bottlenecks due to migrations, introduced diseases, and other effects of colonization. To estimate the effective size of a population, we first estimate the conditional coalescence probability qg, and use the relationship Ng = 1/(2qg). The effective size depends on the sampling scheme, which may over-represent some of the sub-populations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
