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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  • Biology
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  • 1997
TLDR
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TLDR
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References

SHOWING 1-10 OF 34 REFERENCES
Gene flow and selection in a two-locus system.
TLDR
The results are that when the recombination fraction between the loci is of the same order of magnitude as the selection coefficients or smaller, then linkage is important in determining the gene frequencies and a substantial amount of linkage disequilibrium is present in the cline.
The effect on neutral gene flow of selection at a linked locus.
  • D. Petry
  • Biology
    Theoretical population biology
  • 1983
Gene flow past a cline
TLDR
It is shown that a linked cline induces a step in the frequency of a neutral allele, which is proportional to the gradient in neutral allele frequency and to the inverse of the recombination rate.
The effects of linkage and density-dependent regulation on gene flow
The rate of gene flow across a hybrid zone may be reduced by the presence of a physical barrier, by a reduction of population density caused by reduced fitness of hybrids (the “hybrid sink” effect),
Genetic Revolutions, Founder Effects, and Speciation
TLDR
It is argued that, although founder effects may cause speciation under sufficiently stringent conditions, they are only one extreme of a continuous range of possibilities, and divergence may be driven in a variety of ways, without the need for drastic external changes.
Models of speciation by sexual selection on polygenic traits.
  • R. Lande
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1981
TLDR
The models elucidate genetic mechanisms that can initiate or contribute to rapid speciation by sexual isolation and divergence of secondary sexual characters in polygamous species.
Analysis of Hybrid Zones
TLDR
Hybrid zones are narrow regions in which genetically distinct populations meet, mate, and produce hybrids, and models of parapatric speciation, and of Wright's "shifting balance," involve the formation, move­ ment, and modification of hybrid zones.
...
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