The effect of a cline as a barrier to gene flow at closely linked, weakly selected loci is investigated using a continuous diffusion model. 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. A barrier to dispersal or a local region of low abundance has a similar effect (Nagylaki, 1976). The cline will block the flow of neutral alleles over a region of chromosome roughly 2s/t map units long. However, a slightly advantageous allele will be little affected, and must be very tightly linked to be delayed for long.
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Barton NH. Gene flow past a cline. Heredity. 1979;43(3):333-339. doi:10.1038/hdy.1979.86
Barton, N. H. (1979). Gene flow past a cline. Heredity, 43(3), 333–339. https://doi.org/10.1038/hdy.1979.86
Barton, Nicholas H. “Gene Flow Past a Cline.” Heredity 43, no. 3 (1979): 333–39. https://doi.org/10.1038/hdy.1979.86.
N. H. Barton, “Gene flow past a cline,” Heredity, vol. 43, no. 3, pp. 333–339, 1979.
Barton NH. 1979. Gene flow past a cline. Heredity. 43(3), 333–339.
Barton, Nicholas H. “Gene Flow Past a Cline.” Heredity, vol. 43, no. 3, Nature Publishing Group, 1979, pp. 333–39, doi:10.1038/hdy.1979.86.