Spontaneous mutation for life-history traits in Drosophila melanogaster.

Spontaneous mutations accumulated during 80 generations in 94 lines derived from a completely homozygous population of Drosophila melanogaster, all of them maintained by a single brother-sister mating per generation. Three traits were evaluated: early productivity, late productivity, and longevity. Mutational heritabilities were similar for all traits: 3.18 x 10(-3), 3.52 x 10(-3), and 3.38 x 10(-3), respectively. Nine lines were examined, their means being in the upper or lower tails of the distribution of line's means for at least two traits. Reciprocal crosses were made between each line and the control population to estimate line effects. The results can be summarised as follows: all lines carried putative mutations affecting fitness traits; five lines affect the three traits scored; one affects exclusively early productivity; and three affect exclusively late life-history traits (late productivity and longevity). Most mutations were deleterious and recessive, except one that favourably affected early-productivity and was dominant. Additional fitness traits were evaluated, indicating pleiotropy. We have not found mutations with antagonistic effects early and late in life; moreover, positive mutational correlation seems to be the rule.