Effects on fitness components of enhanced expression of elongation factor EF-1alpha in Drosophila melanogaster. I. The contrasting approaches of molecular and population biologists.

We measured the life spans and fecundities of mated female fruit flies that had enhanced expression at higher temperatures of the gene for elongation factor 1 alpha (EF-1 alpha), a gene of known physiological function, and compared those measurements with similar measurements made on control lines at 25 degrees and 29.5 degrees C. We also measured similar effects on the life spans of virgin males and females. The hypothesis that enhanced expression of EF-1 alpha at 29.5 degrees C increases life span was tested by the significance of the treatment-by-temperature interaction effect in factorial ANOVAs and Cox regressions. This effect was significant for mated females only. Treatment females with enhanced expression of EF-1 alpha lived significantly longer and laid significantly fewer eggs early in life than did control females, a result not mediated by possible effects of EF-1 alpha on body weight. There was an effect of treatment independent of the interaction with temperature. Virgin treatment females lived significantly longer at both 25 degrees and 29.5 degrees. In contrast to previous results, enhanced expression of EF-1 alpha had no impact on the life spans of virgin males. Implications are discussed for the evolutionary theory of ailing and for biases introduced into experimental design through the influence of particular theories.