An exploration into the conversion of dominance to additive genetic variance in contrasting environments

Abstract

Premise The evolutionary response of a trait to environmental change depends upon the level of additive genetic variance. It has been long argued that sustained selection will tend to deplete additive genetic variance as favored alleles approach fixation. Non‐additive genetic variance, due to interactions among alleles within and between loci, does not immediately contribute to an evolutionary response. However, shifts in the allele frequencies within and between interacting loci may convert non‐additive variance into additive variance. Here we consider the possibility that an environmental shift may alter allelic interactions in ways that convert dominance into additive genetic variance. Methods We grew a pedigreed population of Brassica rapa in greenhouse and field conditions. The field conditions mimicked agricultural conditions from which the base population was drawn, while the greenhouse featured benign conditions. We used Bayesian models to estimate the additive, dominance, and maternal components of quantitative genetic variance. We also estimated genetic correlations across environments using parental breeding values. Results Although the additive genetic variance was elevated in the greenhouse condition, no consistent pattens emerged that would indicate a conversion of dominance variance. The unusually low genetic variance and broad confidence intervals for the variance estimates obtained through this analysis preclude definitive interpretations. Conclusions Further studies are needed to determine whether between‐environment changes in additive genetic variance can be traced to conversion of dominance variance.

What determines the evolutionary trajectories of wild plant species? Approaches to the study of quantitative fitness‐related traits

“…So, Sibolibane, and Weis (2022) explored how the nature of genetic variance might change depending on the environment, and specifically, the possibility that non‐additive variance (e.g., dominance variance, V D ) could be converted to additive genetic variance ( V A ) and thus subject to selection, depending on the environment. Using a pedigreed population of Brassica rapa grown for three generations with a design that allowed them to separate dominance variance from maternal effect variance, plants were grown in two environments (field conditions mimicking the agricultural conditions of the original population vs. presumably more benign greenhouse conditions) to estimate additive, dominance, and maternal components of genetic variance using Bayesian models.…”