Dominance Variation in the Correlation between Longevity and Heat- Stress Resistance in Drosophila melanogaster

The possible genetic correlation between longevity and knockdown resistance to high temperature (KRHT) was tested in reciprocal backcrosses between nearly-homozygous lines of D. melanogaster. These baselines differ dramatically for KRHT. Because nearly-homozygous lines were used, reciprocal backcrosses were informative to test for dominant versus additive genetic associations between the traits. The line of high KRHT was longer lived than the low KRHT line. The correlation between longevity and KRHT was dependent on the backcross (BC). When a BC was set up with males from the low KRHT line, the most KRHT resistant individuals were in turn the longest-lived flies. However, this was not found in the reciprocal backcross, indicating dominance. Alleles that confer increased KRHT are dominant in the correlation between longevity and KRHT. The between-line variation in the traits studied is consistent with the hypothesis that stress-resistant genotypes correspond to long-lived individuals.