Transgenerational transmission of an environmental modification in quails: changes in phenotypic variance components across three generations

While epigenetic variations can contribute to shaping phenotypic diversity, it can be challenging to isolate and quantify the portion of trait variability under epigenetic influence. In this study we compared the phenotypic responses for different traits of two epilines of Japanese quails (Coturnix japonica) across three generations, using a large sample size. These epilines were built in parallel following (epi +), or not (epi -), an initial genistein ingestion in the ancestors diet and were maintained to harbour a similar genetic structure. Linear models were fitted to extract the fraction of variance allocated to multiple factors such as family, sex and epiline. The latter was found to be significantly associated with body weight. The proportion of phenotypic variance explained by the epiline progressively increased from the first generation (G0) to the last (G2), leading - for example in body weight at slaughter - to an average difference for adult males and females in G2 of 9 grams and 14 grams respectively, between epi + offspring and controls (epi-). Although these findings suggest genetic drift, they could also reveal a possible transgenerational effect of the initial diet disruption. The analysis of variance (ANOVA) of other phenotypes did not display a significant effect of the epiline. This innovative experimental design offered a unique opportunity to better understand the evolution of phenotypic variance and the parameters constituting it across three generations following or not an environmental change.