The barrier to genetic exchange between hybridising populations

@article{Barton1986TheBT,
  title={The barrier to genetic exchange between hybridising populations},
  author={Nicholas H. Barton and Bengt Olle Bengtsson},
  journal={Heredity},
  year={1986},
  volume={57},
  pages={357-376}
}
Suppose that selection acts at one or more loci to maintain genetic differences between hybridising populations. Then, the flow of alleles at a neutral marker locus which is linked to these selected loci will be impeded. We define and calculate measures of the barrier to gene flow between two distinct demes, and across a continuous habitat. In both cases, we find that in order for gene flow to be significantly reduced over much of the genome, hybrids must be substantially less fit, and the… 
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Methods Citations
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Results Citations
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575 Citations

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NEUTRAL GENE FLOW ACROSS SINGLE LOCUS CLINES
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The theoretical results suggest that selection against hybrid formation in the form of fertility selection or assortative mating is more effective in preventing introgression of neutral alleles than is reduction in hybrid viability.
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The introgression of genes carried by a small group of immigrants is studied, and the monomorphic and the polymorphic loci of the recipient population contribute differently to the selection barrier.
The role of hybridization in evolution
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Fisher’s model of stabilizing selection on multiple traits, under which reproductive isolation evolves as a side‐effect of adaptation in allopatry, confirms a priori arguments that while recombinant hybrids are less fit on average, some gene combinations may be fitter than the parents, even in the parental environment.
The reduction of neutral gene flow caused by a selected gene in plant population models
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The analysis clarifies how subpopulations belonging to a rare habitat can maintain local adaptation despite high levels of migration if net selection against multi-locus genotypes is stronger than a threshold which depends on the relative abundances of the two habitats.
The geography of introgression in a patchy environment and the thorn in the side of ecological speciation
TLDR
It is argued that the history of differentiation should ideally be reconstructed with selected loci or neutral loci linked to them, not neutral ones, and some case studies for which the hypothesis of a long speciation was initiated in allopatry are reviewed.
Effects of polymorphism for locally adapted genes on rates of neutral introgression in structured populations.
SINGLE LOCUS CLINES
  • S. Gavrilets
  • Biology
    Evolution; international journal of organic evolution
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It is shown that single locus clines arising from fertility and viability selection against heterozygotes also describe hybrid zones arising in some models of selection against rare phenotypes.
Identifying Loci Under Selection Against Gene Flow in Isolation-with-Migration Models
TLDR
An isolation-with-migration model that explicitly provides for variation among genomic regions in migration rates and/or rates of genetic drift is developed that allows for loci to fall into any of multiple groups, each characterized by a different set of parameters, thus relaxing the assumption that all loci share the same demography.
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