Most of the variation with a genetic basis that differentiates individuals within a species or population can be traced to the presence of different alleles at a large number of loci. Evolution of such quantitative phenotypes can therefore involve many loci distributed throughout the genome. For many phenotypes, we can understand how different allelic combinations result in phenotypic variation by studying how variation is produced in developmental pathways. We can also use such developmental understanding to determine whether and why specific loci have been involved in the evolution of an adult phenotype.

We use Drosophila as a model system to build this connection between variation at quantitative loci, developmental pathways, and evolving adult phenotypes. Specifically, we study the wing and overall body size, phenotypes where selection has played a role in producing the pattern of variation observed in nature. To study these phenotypes, we map loci with quantitative effects and analyze how allelic variation at these loci produces variation in developmental signal transduction pathways. Using a combination of molecular assays and statistical modeling approaches we then study how variation in these developmental genetic pathways translates into variation in the wing and in body size.