Epistasis Is a Major Determinant of the Additive Genetic Variance in Mimulus guttatus

Abstract

The influence of genetic interactions (epistasis) on the genetic variance of quantitative traits is a major unresolved problem relevant to medical, agricultural, and evolutionary genetics. The additive genetic component is typically a high proportion of the total genetic variance in quantitative traits, despite that underlying genes must interact to determine phenotype. This study estimates direct and interaction effects for 11 pairs of Quantitative Trait Loci (QTLs) affecting floral traits within a single population of Mimulus guttatus. With estimates of all 9 genotypes for each QTL pair, we are able to map from QTL effects to variance components as a function of population allele frequencies, and thus predict changes in variance components as allele frequencies change. This mapping requires an analytical framework that properly accounts for bias introduced by estimation errors. We find that even with abundant interactions between QTLs, most of the genetic variance is likely to be additive. However, the strong dependency of allelic average effects on genetic background implies that epistasis is a major determinant of the additive genetic variance, and thus, the population’s ability to respond to selection.

Naturally segregating loci exhibit epistasis for fitness

“…The per cent of explained variance (partial R 2 ) for each term and significance of posthoc comparisons were determined with the 'pamer.fnc' and 'mcposthoc.fnc' functions, respectively, ('LMERConvenienceFunctions' package). Greenhouse data come from a previous study [16] (details of analysis can be found in the electronic supplementary material table files).…”

How does selfing affect the genetic variance of quantitative traits? An updated meta‐analysis on empirical results in angiosperm species

“…However, it has been shown that V A includes more than just additive genotypic values. Functional epistasis can also greatly contribute to this genetic component of variance (Cheverud and Routman 1995;Carter et al 2005;Monnahan and Kelly 2015); if there is epistasis, the effect of an allele will depend on the genetic background at other loci. Because selfing decreases the efficiency of recombination and thus favors the maintenance of allelic combinations between loci, functional epistasis may be more common in inbreeding populations.…”

Estimation of additive and epistatic gene effects of doubled haploid lines of winter oilseed rape (Brassica napus L.)

“…parental, F 1 , F 2 , BC 1 . However, more effective estimation of additive and epistasis effects is on the basis of homozygous lines (Bocianowski 2012a(Bocianowski , 2013(Bocianowski , 2014Bocianowski and Nowosad 2015;Kim et al 2015;Monnahan and Kelly 2015;Ober et al 2015).…”