Nonparametric Estimation of Recent Demographic History from Segments of Identity by Descent

• Activity Number: 248
• Type: Contributed
• Date/Time: Monday, August 10, 2015 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Sharon Browning* and Brian Browning
• Companies: University of Washington and University of Washington
• Keywords: genetic data ; effective population size ; identity by descent ; linkage disequilibrium ; genome wide SNP array ; whole genome sequence data

Abstract

Long segments of identity by descent (IBD) can be inferred with high confidence from genotype data. The number of detected IBD segments and the distribution of their lengths contain information about effective population size over the last fifty or more generations. Effective population size is a critical parameter that is necessary for understanding selective forces and demographic history. We present a method for estimating recent effective population sizes using inferred IBD segments. An attractive feature of this new method is that it is non-parametric, allowing the data to reveal the trajectory of historical effective population size without requiring a priori assumptions about the trajectory shape. We apply our method to sequence data from the UK, and to SNP array data from Finland. We estimate the effective population size of European-ancestry individuals in the UK 4 generations ago to be 8 million and the effective population size of Finland 4 generations ago to be 0.7 million.