THE INBREEDING DECLINE AND AVERAGE DOMINANCE OF GENES AFFECTING MALE LIFE-HISTORY CHARACTERS IN DROSOPHILA-MELANOGASTER

This paper describes the results of assays of male life-history charac ters in a large outbred laboratory population of D. melanogaster. Line s of flies homozygous for the entire third chromosome and lines of fli es carrying two different third chromosomes were assayed for age-speci fic male mating ability (MMA), age-specific survivorship, male fertili ty, and body mass. The results of these assays were used to calculate the inbreeding decline associated with each of these traits, the avera ge dominance of deleterious alleles that affect the traits, the genoty pic and environmental components of variance for the homozygous lines, and phenotypic and genotypic correlations among the characters. Signi ficant inbreeding decline was found for all characters except the Gomp ertz intercept and fertility. Early and late MMA show larger effects o f inbreeding than any other trait. The inbreeding load for MMA is abou t the same magnitude as that for egg-to-adult viability, but is substa ntially less than that associated with total fitness. The estimated in breeding decline and average dominance of male life-history characters are comparable to estimates for other Drosophila fitness components.