Admixed populations have been used for inferring migrations, detecting natural selection, and finding disease genes. These applications often use a simple statistical model of admixture rather than a modeling perspective that incorporates a more realistic history of the admixture process. Here, we develop a general model of admixture that mechanistically accounts for complex historical admixture processes. We consider two source populations contributing to the ancestry of a hybrid population, potentially with variable contributions across generations. For a random individual in the hybrid population at a given point in time, we study the fraction of genetic admixture originating from a specific one of the source populations by computing its moments as functions of time and of introgression parameters. We show that very different admixture processes can produce identical mean admixture proportions, but that such processes produce different values for the variance of the admixture proportion. When introgression parameters from each source population are constant over time, the long-term limit of the expectation of the admixture proportion depends only on the ratio of the introgression parameters. The variance of admixture decreases quickly over time after the source populations stop contributing to the hybrid population, but remains substantial when the contributions are ongoing. Our approach will facilitate the understanding of admixture mechanisms, illustrating how the moments of the distribution of admixture proportions can be informative about the historical admixture processes contributing to the genetic diversity of hybrid populations. Received July 14, 2011. Accepted September 23, 2011. Copyright © 2011 by the Genetics Society of America Available freely online through the author-supported open access option. Related articles Issue Highlights : ISSUE HIGHLIGHTS Genetics December 2011 189 : NP Full Text Full Text (PDF) « Previous | Next Article » Table of Contents OPEN ACCESS ARTICLE This Article Published online before print October 3, 2011 , doi: 10.1534/genetics.111.132787 Genetics December 1, 2011 vol. 189 no. 4 1413-1426 Free via Open Access: OA » Abstract OA Full Text Full Text (PDF) Supporting Information Classifications Investigations Population and Evolutionary Genetics Services Email this article to a friend Alert me when this article is cited Alert me if a correction is posted Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Download to citation manager Citing Articles Load citing article information Google Scholar Articles by Verdu, P. PubMed PubMed citation Articles by Verdu, P. Related Content Related articles in this journal Load related web page information This Months's Issue December 2011, 189 (4) Alert me to new issues of Genetics ABOUT SUBSCRIBE INFO FOR AUTHORS ONLINE SUBMISSION EDITORIAL BOARD CONTACT ALERTS HELP ADVERTISING RSS Help Contact Us International Access Link Print ISSN: 0016-6731 Online ISSN: 1943-2631 Copyright © 2011 by the Genetics Society of America phone: 412-268-1812 fax: 412-268-1813 email: genetics-gsa@andrew.cmu.edu

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