The probability of fixation of a favorable mutation is reduced if selection at other loci causes inherited variation in fitness. A general method for calculating the fixation probability of an allele that can find itself in a variety of genetic backgrounds is applied to find the effect of substitutions, fluctuating polymorphisms, and deleterious mutations in a large population. With loose linkage, r, the effects depend on the additive genetic variance in relative fitness, var(W), and act by reducing effective population size by (N/Ne) = 1 + var(W)/2r2. However, tightly linked loci can have a substantial effect not predictable from Ne. Linked deleterious mutations reduce the fixation probability of weakly favored alleles by exp (-2U/R), where U is the total mutation rate and R is the map length in Morgans. Substitutions can cause a greater reduction: an allele with advantage s < scrit = (pi 2/6) loge (S/s) [var(W)/R] is very unlikely to be fixed. (S is the advantage of the substitution impeding fixation.) Fluctuating polymorphisms at many (n) linked loci can also have a substantial effect, reducing fixation probability by exp [square root of 2Kn var(W)/R] [K = -1/E((u-u)2/uv) depending on the frequencies (u,v) at the selected polymorphisms]. Hitchhiking due to all three kinds of selection may substantially impede adaptation that depends on weakly favored alleles.
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Barton NH. Linkage and the limits to natural selection. Genetics. 1995;140(2):821-841. doi:http://www.genetics.org/content/140/2/821.long
Barton, N. H. (1995). Linkage and the limits to natural selection. Genetics, 140(2), 821–841. http://www.genetics.org/content/140/2/821.long
Barton, Nicholas H. “Linkage and the Limits to Natural Selection.” Genetics 140, no. 2 (1995): 821–41. http://www.genetics.org/content/140/2/821.long.
N. H. Barton, “Linkage and the limits to natural selection,” Genetics, vol. 140, no. 2, pp. 821–841, 1995.
Barton NH. 1995. Linkage and the limits to natural selection. Genetics. 140(2), 821–841.
Barton, Nicholas H. “Linkage and the Limits to Natural Selection.” Genetics, vol. 140, no. 2, Genetics Society of America, 1995, pp. 821–41, doi:http://www.genetics.org/content/140/2/821.long.
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