Relation between homozygous viability and average dominance in Drosophila melanogaster.

The laboratory populations have been described by CHUNG (1962) and FRIEDMAN (1964). The wild populations came from six localities in two regions. Manoa, Waikiki, and Kapahulu are three suburbs of Honolulu, Hawaii, and Frank's, Kapec, and Capitol are three sites in Madison, Wisconsin. Within a region, the localities are 1-3 miles apart. Each locality was represented by a collection of about 200 females, whose descendants were maintained in 8 half-pint bottles, with mixing at each transfer. The collections included a minority of D. simulans which gradually were eliminated without artificial selection. Basc tests were described by FRIEDMAN (19%). Second chromosomes were studied by the methods of CHUNG (1%2), in which the last generation comes from the mating cn bwD/+ 8 X C y O/+ 9 , where Cy 0 denotes Curly wings and complex inversions and the cn bwD chromosome was selected for high sensitivity to the segregation-distorter (SD) locus (SANDLER and HIRAIZUMI 1959). The grandparental mating was C y O/S 8 x +/f 9 , and various inbreeding levels were derived in the last generation by taking chromosomes identical by descent ( F = %), from the same grandmother ( F = %), from grandmothers who were sibs ( F = %), and from unrelated grandmothers ( F = 0), the inbreeding coefficient F being based on the assumption that the second chromosome makes up one-half of the autosomal genome. In addition, an interpopulational outcross ( H = %) was made in the last generation, where H denotes the fraction of the autosomal genome that is an F, hybrid. This experiment was carried out as a twice-replicated balanced incomplete block design with three pairs of populations in each of five blocks, each pair involving two intrapopulational and one interpopulational sets of cultures, the different levels of inbreeding within each pair being carried out concurrently. The number of chromosomes tested per subset was about five, and levels F = 0 and H = '/z were cyclical permutations of the same chromosomes used for the inbreeding tests. The mating type is called