Integrating molecular mechanisms into quantitative genetics to understand consistent individual differences in behavior

•The study of animal personality is concerned with both variation and plasticity.•Quantitative genetics provides a conceptual framework for personality.•Recent studies have identified genes related to behavioral variation and plasticity.•A challenge is to integrate molecular mechanisms into quantitative genetic theory.

It is now well appreciated that individual animals behave differently from one another and that individual differences in behaviors - personality differences - are maintained through time and across situations. Quantitative genetics has emerged as a conceptual basis for understanding the key ingredients of personality: (co)variation and plasticity. However, the results from quantitative genetic analyses are often divorced from underlying molecular or other proximate mechanisms. This disconnect has the potential to impede an integrated understanding of behavior and is a disconnect present throughout evolutionary ecology. Here we discuss some of the main conceptual connections between personality and quantitative genetics, the relationship of both with genomic tools, and areas that require integration. With its consideration of both trait variation and plasticity, the study of animal personality offers new opportunities to incorporate molecular mechanisms into both the trait partitioning and reaction norm frameworks provided by quantitative genetics.