Quantitative traits

Abstract

Quantitative traits are phenotypic traits that are determined, jointly with the environment, by many genes of small effect. Most of the directly observable individual characteristics are quantitative traits. Differences in quantitative traits can give valuable signals on existence of separate stock components. Compared to neutral genetic markers, quantitative traits are more sensitive to population structure and may suggest differences where neutral genetic markers fail to show any. However, quantitative traits may also show differences where demographic separation is weak. An important challenge is to understand how the environment influences quantitative traits. Representing quantitative traits as reaction norms makes their dependence on the environment explicit and thereby facilitates their use in stock identification.