Newfoundland and Labrador: A mosaic founder population of an Irish and British diaspora from 300 years ago.

The founder population of Newfoundland and Labrador (NL) is a unique genetic resource, in part due to geographic and cultural isolation, where historical records describe a migration of European settlers to NL in the 18th and 19th centuries. However, the fine-scale genetic structure and ancestry of the population has not been well described. Here, we leverage dense genome-wide SNP data on 1,807 NL individuals to reveal fine-scale genetic structure in NL that is clustered around coastal communities and correlated with Christian denomination. We show that the majority of NL European ancestry can be traced back to the south-east and south-west of Ireland and England. We date a substantial population size bottleneck approximately 10-15 generations ago in NL, associated with increased haplotype sharing and autozygosity. Our results elucidate novel insights into the population history of NL and demonstrate evidence of a population conducive to further genetic studies and biomarker discovery. ### Competing Interest Statement E.G., and G.C received financial consumable support from Sequence Bioinformatics, Inc. to support research efforts performed during the development of the manuscript. H.Z., M.E.M, S.D., S.M., R.A.L., G.M., R.R. and M.S.P. are full time employees and shareholders of Sequence BioInformatics, Inc. J.C.S., and A.S.L. are paid scientific consultants employed by Sequence BioInformatics, Inc. M.M, S.OR., A.M.M., L.C.B, and W.B. declare no competing interests.