Abstract
Discriminating between genetic and environmental causes of phenotypic variation is an essential requirement for understanding the evolutionary potential of populations. However, the extent to which genetic variation differs among conspecific groups and environments during ontogeny has rarely been investigated. In this study, the genetic basis of body mass was measured in three divergent strains of brook charr (Salvelinus fontinalis) in different rearing environments and at different time periods. The results indicate that body mass was a heritable trait in all strains but that the level of heritability greatly differed among strains. Moreover, heritability estimates of each strain varied differently according to environmental rearing conditions, and cross-environments correlations were all significantly lower than unity, indicating strain-specific patterns of genotype–environment interactions. Heritability estimates also varied throughout ontogeny and decreased by 50% from 9 to 21 months of age. This study highlights the divergence in genetic architecture and evolutionary potential among these strains and emphasizes the importance of considering the strain-specific potential of the response to selection according to environmental variation.
Highlights
Discriminating between genetic and environmental causes of phenotypic variation is an essential requirement for understanding the evolutionary potential of populations
The ability of organisms to express different genes under different environmental conditions allows the maintenance of additive genetic variance, but plastic response may counteract response to selection and reduce the speed of evolutionary changes (Wilson et al 2006), which may be consequential in applied contexts as well
No significant environmental effect was detected in the domestic strain (P = 0.14; Figure 2), whereas we observed a significant genetic covariance and a high correlation between the additive components measured in the two environments
Summary
Discriminating between genetic and environmental causes of phenotypic variation is an essential requirement for understanding the evolutionary potential of populations. In the current context of increasing anthropogenic selection pressures, such as climate change or artificial selection through exploitation, it is becoming increasingly important to document the evolutionary potential of populations (Smith and Bernatchez 2008; Visser 2008), i.e., their capacity to adapt to changing environmental conditions in the long term. To this end, one needs to assess the evolutionary and plastic environmental components underlying phenotypic variation, which is best achieved using a quantitative genetics approach. Understanding the evolutionary potential of brook charr is of fundamental interest both because it can be sensitive to various conditions and because of implications for its management in aquaculture
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