Domestication—From behaviour to genes and back again

Abstract

During domestication, animals have adapted with respect to behaviour and an array of other traits. This tends to give rise to a specific domestication phenotype, involving similar changes in colour, size, physiology and behaviour among different species. Hence, domestication offers a model for understanding the genetic mechanisms involved in the trade-off between behaviour and other traits in response to selection. We compared the behaviour and other phenotypic traits of junglefowl and white leghorn layers, selected for egg production (and indirectly for growth). To examine the genetic mechanisms underlying the domestication-related differences, we carried out a genome scan for quantitative trait loci (QTLs) affecting behaviour and production traits in F2-birds of a junglefowl × white leghorn intercross. Several significant or suggestive QTLs for different production traits were located and some of these coincided with QTLs for behaviour, suggesting that QTLs with pleiotropic effects (or closely linked QTLs) may be important for the development of domestication phenotypes. Two genes and their causative mutations for plumage colouration have been identified, and one of these has a strong effect on the risk of being a victim of feather pecking, a detrimental behaviour disorder. It is likely that fast and large evolutionary changes in many traits simultaneously may be caused by mutations in regulatory genes, causing differences in gene expression orchestration. Modern genomics paired with analysis of behaviour may offer a route for understanding the relation between behaviour and production and predicting possible side-effects of breeding programs.