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

Abstract

The mating system of a species is expected to have important effects on its genetic diversity. In this article, we explore the effects of partial selfing on the equilibrium genetic variance V , 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. 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 V , 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 V , L, and δ. Simulations indicate that the values of V , L, and δ are little affected by assumptions regarding the number of possible alleles per locus.

Effect of partial selfing and polygenic selection on establishment in a new habitat

“…The interplay between partial selfing and polygenic selection in large populations has been analyzed via different theoretical approaches (Kondrashov 1985;Charlesworth et al 1990Charlesworth et al , 1991Lande et al 1994;Kelly 1999Kelly , 2007Roze 2015;Lande and Porcher 2015;Abu-Awad and Roze 2018). A key challenge is to find tractable and accurate approximations for the multilocus associations that emerge due to partial selfing even in the absence of linkage.…”

Epistasis, inbreeding depression and the evolution of self-fertilization

“…Our second fitness function corresponds to stabilizing selection acting on an arbitrary number n of quantitative traits, with a symmetrical, Gaussian-shaped fitness function. The general model is the same as in Abu Awad and Roze (2018): r αj denotes the effect of allele 1 at locus j on trait α, and we assume that the different loci have additive effects on traits:…”

“…Non-Gaussian stabilizing selection. The last example we examined is a generalization of the fitness function given by equation 14, in order to introduce a coefficient Q affecting the shape of the fitness peak (e.g., Martin and Lenormand, 2006a;Tenaillon et al, 2007;Gros et al, 2009;Roze and Blanckaert, 2014;Abu Awad and Roze, 2018):…”

“…Concerning the spread of selfing modifier alleles, the results were qualitatively similar to the multiplicative model, except that, for parameter values where full outcrossing is not stable, the evolutionarily stable selfing rate tended to be slightly below 1 under synergistic epistasis (whereas it would have been at exactly 1 in the absence of epistasis). Other models explored the effect of partial selfing on inbreeding depression generated by polygenic quantitative traits under stabilizing selection (Lande and Porcher, 2015;Abu Awad and Roze, 2018). This type of model typically generates distributions of epistatic interactions across loci, including possible compensatory effects between mutations.…”

“…Although the expressions obtained can become complicated for intermediate selfing rates, we will see that the condition determining whether selfing can spread in a fully outcrossing population often remains relatively simple. Notably, our model allows us to disentangle the effects of additive-by-additive, additive-by-dominance and dominance-by-dominance epistatic interactions on inbreeding depression and selection for selfing -while the models used by Charlesworth et al (1991), Lande and Porcher (2015) and Abu Awad and Roze (2018) impose certain relations between these quantities. The cases of fixed, synergistic epistasis and of stabilizing selection acting on quantitative traits (Fisher's geometric model) will be considered as special cases, for which we will also present individual-based simulation results.…”