A method for identifying a quantitative trait loci for a complex trait that is exhibited by a plurality of organisms in a population. The population is divided into a plurality of sub-populations using a classification scheme. Depending on what is known about the population, either a supervised or unsupervised classification is used. The classification scheme is derived from a plurality of cellular constituent measurements obtained from each organism in the population. For each sub-population in the plurality of sub-populations, a quantitative genetic analysis is performed on the sub-population in order to identify one or more quantitative trait loci for the complex trait.