![]() ![]() By generation 4, however, owing to recombination events that stochastically dissociate the trait loci from the overall genetic admixture, the genetic admixture has been decoupled from the phenotype, so that some of the individuals with the highest trait values have among the lowest admixture coefficients for source population 1, and the correlation between phenotype and overall genetic admixture has dissipated ( r = − 0.09 ).Ībbott R, Albach D, Ansell S, Arntzen JW, Baird SJE, Bierne N, Boughman J, Brelsford A, Buerkle CA, Buggs R, et al., 2013. Initially, in generation 2, a strong correlation exists between admixture and phenotype ( r = 0.96 ). Lines connecting generations are displayed in four colors, representing four mating pairs. After generation 1, positive assortative mating by phenotype proceeds in the admixed population. Individuals are depicted as pairs of chromosomes with the ancestral sources of those chromosomes short vertical lines along the chromosome indicate the three loci that contribute to the phenotype. The phenotype is represented by the shading of a box. Three loci contribute additively to the genetic architecture of the phenotype each allele derived from source population 1 contributes a value of 1 to the phenotype. For a quantitative phenotype, source population 1 begins with a high trait value of 6 and source population 2 has a low trait value of 0. In generation 0, an admixture process begins with females from one population (source 1, left) and males from another (source 2, right). ![]() It follows that a social categorization based on such a trait is increasingly uninformative about genetic ancestry and about other traits that differed between source populations at the onset of admixture.Īdmixture assortative mating mechanistic model population genetics.Ī schematic of an admixture process with positive assortative mating by a phenotype initially correlated with admixture levels. The mechanistic framework suggests that in an admixed population, a trait that initially differed between source populations might serve as a reliable proxy for ancestry for only a short time, especially if the trait is determined by few loci. Positive assortative mating attenuates the process of dissociation relative to a scenario in which mating is random with respect to genetic admixture and with respect to phenotype. We find that it is possible for the decoupling of genetic ancestry and phenotype to proceed quickly, and that it occurs faster if the phenotype is driven by fewer loci. We analyze the behavior of the mechanistic model in relation to the model parameters. We devise a mechanistic model, consisting of an admixture model, a quantitative trait model, and a mating model. Here, we aim to develop an understanding of the joint dynamics of admixture levels and phenotype distributions in an admixed population. However, genotypes or phenotypes initially associated with ancestry in one specific source population have been seen to decouple from overall admixture levels, so that they no longer serve as proxies for genetic ancestry. Such phenotypes might possess ongoing significance in social categorizations of individuals, owing in part to perceived continuing correlations with ancestry. Particularly in the context of recent and ongoing admixture, such differences are sometimes taken to serve as markers of ancestry for individuals-that is, phenotypes initially associated with the ancestral background in one source population are assumed to continue to reflect ancestry in that population. In genetic admixture processes, source groups for an admixed population possess distinct patterns of genotype and phenotype at the onset of admixture. ![]()
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