Limits to the rate of adaptive substitution in sexual populations.
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Heritable variance v in log fitness due to unlinked loci reduces Λ by e⁻⁴(v) under polygamy and e⁻⁸ (v) under monogamy.We also consider the effect of sweeps on neutral diversity and show that, while even occasional sweeps can greatly reduce neutral diversity, this effect saturates as sweeps become more common-diversity can be maintained even in populations experiencing very strong interference.Our results indicate that for some organisms the rate of adaptive substitution may be primarily recombination-limited, depending only weakly on the mutation supply and the strength of selection.
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Affiliation: Institute of Science and Technology Austria, Klosterneuburg, Austria. dbw@ist.ac.at
ABSTRACT In large populations, many beneficial mutations may be simultaneously available and may compete with one another, slowing adaptation. By finding the probability of fixation of a favorable allele in a simple model of a haploid sexual population, we find limits to the rate of adaptive substitution, Λ, that depend on simple parameter combinations. When variance in fitness is low and linkage is loose, the baseline rate of substitution is Λ₀ = 2NU Related in: MedlinePlus |
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Mentions: Above, we have focused on the case in which all beneficial mutations provide the same selective advantage . Using simulations, we have also investigated the effect of allowing exponentially distributed selective advantages. ([10] and [78] conduct similar studies for asexual populations.) Figure 7 shows that for both weak and strong interference, allowing for variation in makes little difference to the rate of adaptation. Populations with an exponential distribution of mutational effects with mean evolve only slightly slower than populations with a fixed value , and show nearly the same scaling with the strength of selection. |
View Article: PubMed Central - PubMed
Affiliation: Institute of Science and Technology Austria, Klosterneuburg, Austria. dbw@ist.ac.at