Joint Effects of Self-Fertilization and Population Structure on Mutation Load, Inbreeding Depression and Heterosis

Abstract The subdivision of a species into local populations causes its response to selection to change, even if selection is uniform across space. Population structure increases the frequency of homozygotes and therefore makes selection on homozygous effects more effective. However, population subdivision can increase the probability of competition among relatives, which may reduce the efficacy of selection. As a result, the response to selection can be either increased or decreased in a subdivided population relative to an undivided one, depending on the dominance coefficient FST and whether selection is hard or soft. Realistic levels of population structure tend to reduce the mean frequency of deleterious alleles. The mutation load tends to be decreased in a subdivided population for recessive alleles, as does the expected inbreeding depression. The magnitude of the effects of population subdivision tends to be greatest in species with hard selection rather than soft selection. Population structure can play an important role in determining the mean fitness of populations at equilibrium between mutation and selection.

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Lethals in subdivided populations

Genetics Research ◽

10.1017/s0016672305007676 ◽

2005 ◽

Vol 86 (1) ◽

pp. 41-51 ◽

Cited By ~ 13

Author(s):

SYLVAIN GLÉMIN

Keyword(s):

Population Structure ◽

Population Size ◽

Inbreeding Depression ◽

Deleterious Mutations ◽

Mutation Load ◽

General Picture ◽

Analytical Approximations ◽

Size Population ◽

Subdivided Populations ◽

Numerical Approaches

The fate of lethal alleles in populations is of interest in evolutionary and conservation biology for several reasons. For instance, lethals may contribute substantially to inbreeding depression. The frequency of lethal alleles depends on population size, but it is not clear how it is affected by population structure. By analysing the case of the infinite island model by numerical approaches and analytical approximations it is shown that, like population size, population structure affects the fate of lethal alleles if dominance levels are low. Inbreeding depression caused by such alleles is also affected by the population structure, whereas the mutation load is only weakly affected. Heterosis also depends on population structure, but it always remains low, of the order of the mutation rate or less. These patterns are compared with those caused by mildly deleterious mutations to give a general picture of the effect of population structure on inbreeding depression, heterosis, and the mutation load.

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Effects of partial selfing on the equilibrium genetic variance, mutation load and inbreeding depression under stabilizing selection

10.1101/180000 ◽

2017 ◽

Author(s):

Diala Abu Awad ◽

Denis Roze

Keyword(s):

Inbreeding Depression ◽

Evolutionary Biology ◽

Genetic Variance ◽

Stabilizing Selection ◽

Genetic Associations ◽

Mutation Load ◽

Recombination Rates ◽

Self Fertilization ◽

Selected Traits ◽

Peer Community

ABSTRACTThis preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100041).The mating system of a species is expected to have important effects on its genetic diversity. In this paper, we explore the effects of partial selfing on the equilibrium genetic variance Vg, mutation load L and inbreeding depression δ under stabilizing selection acting on a arbitrary number n of quantitative traits coded by biallelic loci with additive effects. Overall, our model predicts a decrease in the equilibrium genetic variance with increasing selfing rates; however, the relationship between self-fertilization and the variables of interest depends on the strength of associations between loci, and three different regimes are observed. When the U/n ratio is low (where U is the total haploid mutation rate on selected traits) and effective recombination rates are sufficiently high, genetic associations between loci are negligible and the genetic variance, mutation load and inbreeding depression are well predicted by approximations based on single-locus models. For higher values of U/n and/or lower effective recombination, moderate genetic associations generated by epistasis tend to increase Vg, L and δ, this regime being well predicted by approximations including the effects of pairwise associations between loci. For yet higher values of U/n and/or lower effective recombination, a different regime is reached under which the maintenance of coadapted gene complexes reduces Vg, L and δ. Simulations indicate that the values of Vg, L and δ are little affected by assumptions regarding the number of possible alleles per locus.

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Self-Fertilization and Genetic Population Structure in a Colonizing Land Snail

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.70.4.1186 ◽

1973 ◽

Vol 70 (4) ◽

pp. 1186-1190 ◽

Cited By ~ 73

Author(s):

R. K. Selander ◽

D. W. Kaufman

Keyword(s):

Population Structure ◽

Land Snail ◽

Genetic Population Structure ◽

Genetic Population ◽

Self Fertilization

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The mutation load under tetrasomic inheritance and its consequences for the evolution of the selfing rate in autotetraploid species

Genetics Research ◽

10.1017/s0016672399003845 ◽

1999 ◽

Vol 74 (1) ◽

pp. 31-42 ◽

Cited By ~ 59

Author(s):

J. RONFORT

Keyword(s):

Inbreeding Depression ◽

Deleterious Mutation ◽

Stable State ◽

Approximate Solutions ◽

Balance Model ◽

Deleterious Mutations ◽

Selfing Rate ◽

Mutation Load ◽

Mean Fitness ◽

The Mean

Single-locus equilibrium frequencies of a partially recessive deleterious mutation under the mutation–selection balance model are derived for partially selfing autotetraploid populations. Assuming multiplicative fitness interactions among loci, approximate solutions for the mean fitness and inbreeding depression values are also derived for the multiple locus case and compared with expectations for the diploid model. As in diploids, purging of deleterious mutations through consanguineous matings occurs in autotetraploid populations, i.e. the equilibrium mutation load is a decreasing function of the selfing rate. However, the variation of inbreeding depression with the selfing rate depends strongly on the dominance coefficients associated with the three heterozygous genotypes. Inbreeding depression can either increase or decrease with the selfing rate, and does not always vary monotonically. Expected issues for the evolution of the selfing rate consequently differ depending on the dominance coefficients. In some cases, expectations for the evolution of the selfing rate resemble expectations in diploids; but particular sets of dominance coefficients can be found that lead to either complete selfing or intermediate selfing rates as unique evolutionary stable state.

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