Abstract
Non-genetic influences on phenotypic traits can affect our interpretation of genetic variance and the evolutionary potential of populations to respond to selection, with consequences for our ability to predict the outcomes of selection. Long-term population surveys and experiments have shown that quantitative genetic estimates are influenced by nongenetic effects, including shared environmental effects, epigenetic effects, and social interactions. Recent developments to the “animal model” of quantitative genetics can now allow us to calculate precise individual-based measures of non-genetic phenotypic variance. These models can be applied to a much broader range of contexts and data types than used previously, with the potential to greatly expand our understanding of nongenetic effects on evolutionary potential. Here, we provide the first practical guide for researchers interested in distinguishing between genetic and nongenetic causes of phenotypic variation in the animal model. The methods use matrices describing individual similarity in nongenetic effects, analogous to the additive genetic relatedness matrix. In a simulation of various phenotypic traits, accounting for environmental, epigenetic, or cultural resemblance between individuals reduced estimates of additive genetic variance, changing the interpretation of evolutionary potential. These variances were estimable for both direct and parental nongenetic variances. Our tutorial outlines an easy way to account for these effects in both wild and experimental populations. These models have the potential to add to our understanding of the effects of genetic and nongenetic effects on evolutionary potential. This should be of interest both to those studying heritability, and those who wish to understand nongenetic variance.
Highlights
Genetic and nongenetic sources of phenotypic variation and similarity between individuals are often studied in isolation, with different research aims
For tail-fin colour, we found a small but significant amount of variance due to social connections (Vc = 0.491, SE = 0.08, p
The simulation that we show here is an oversimplified view of how epigenetics could be measured, but is used here to illustrate how such effects could be accounted for
Summary
Genetic and nongenetic sources of phenotypic variation and similarity between individuals are often studied in isolation, with different research aims. Laboratory experiments have demonstrated genetic and nongenetic sources of similarity [1], but the use of fixed genetic and/or environmental backgrounds [2,3] can limit their relevance in nature. Studies in wild populations are more biologically realistic, but cannot control for all sources of variation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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