Selection on the Genes that Control Complex Traits
Although many studies provide examples of evolutionary processes such as balancing selection or deleterious polymorphism, the relative importance of these processes for phenotypic variation is unclear. To understand the evolutionary forces that influence complex trait variation, we cloned an ecologically important QTL in natural populations, and then measured the fitness of alleles in the populations where they evolved. Ecological measurements of selection indicate that this polymorphism is influenced by spatially heterogeneous natural selection. Finally, we examined the relationship between flux and protein polymorphism in this pathway, showing that flux control is focused in the first enzymatic step, and that flux control of these defensive phenotypes is robust across environmental treatments. Furthermore, signatures of selection showed that this enzyme is the only one in the pathway that shows evidence of selection.