Parent-offspring regression and extremeenvironments

Abstract

The parent-offspring regression coefficient (narrow heritability) has often been reported to increase with the extremity of environmental conditions. This is frequently interpreted as evidence for the expression of ‘new genes’ under novel environmental conditions. Strictly speaking, however, the parameters of the additive-dominance model of quantitative inheritance only have meaning under a given set of environmental conditions. It is not clear what a change of parameter values, in response to a change of experimental conditions, means in terms of biological processes going on beneath the phenotypic level. The parent-offspring regression coefficient is therefore reconsidered here from the perspective of a biological model of gene expression. It is demonstrated that the parent-offspring regression coefficient can increase directly with the average value of the environmental contribution to the phenotype. More generally, an increase in the strength of parent-offspring regression with extremity of the environment does not necessarily indicate that any change has taken place in the genetic basis of phenotypic value. © The Genetical Society of Great Britain.