Experimentally determined, two locus fitnesses of Drosophila melanogaster males.

A pilot demonstration of experimental fitness estimation utilizing pedigree data from D. melanogaster was described. Fitnesses were obtained for the male segregants of the two "complex loci," spineless-spineless aristapedia and radius incompletus-inturned. A good fit between selection model and data was obtained, perhaps because the experimental design largely eliminated concerns of frequency or density-dependent selection and assortative mating. The selection model assumed that net fitness was divided into two components: an "early" component operative from conception to the time of observation in the generation interval, and a late component operative from the time of observation to the time of gamete pool formation. These fitness components were roughly descriptive of the physiological components viability and reproductive ability. No simple systematic relationship between the fitness of two-locus genotypes and the marginal one-locus fitness emerged. These conclusions were based on relatively precise (by current standards) fitness estimates. It was argued that pedigree data is highly desirable for fitness estimation.