Abstract
This paper summarizes three experiments on the genetic manipulation of fitness components involved in the evolution of lifespan through the introduction of an additional copy of the gene for elongation factor EF-1 alpha into the genome of Drosophila melanogaster. The first experiment checked a prior claim that enhanced expression of elongation factor increased the lifespan of virgin male fruitflies. It used inbred stocks; three treatment and three control lines were available. The second experiment put one treatment and one control insert into different positions on the third chromosome, then measured the influence of six genetic backgrounds on treatment effects in healthier flies. The third experiment put six treatment and six control inserts into the genetic background whose lifespan was most sensitive to the effects of treatment in the second experiment, then measured the influence of insert positions on treatment effects in healthy flies. The treatment never increased the lifespan of virgin males. It increased the lifespan of mated females in inbred flies reared to eclosion at 25 degrees, reduced it in the positions experiment, and made no difference to lifespan in the backgrounds experiment. When it increased lifespan, it reduced fecundity. In inbred flies and in the positions experiment, the treatment reduced dry weight at eclosion of females. Marginal effects of gene substitutions on tradeoffs were measured directly. The results suggest that enhanced expression of elongation factor makes local changes within the bounds of tradeoffs that are given by a pre-existing physiological structure whose basic nature is not changed by the treatment.
