Analysis of the Genetic Structure of Life History of Drosophila melanogaster Using Recombinant Extracted Lines

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Abstract
A model for the evolution of senescence known as “antagonistic pleiotropy” makes the specific prediction that there should be a negative genetic correlation between early- and late-age traits associated with fitness. This model has previously been tested by classical quantitative-genetic means including sib-analysis and artificial selection. We used the approach of chromosome extraction, which has both advantages and disadvantages compared to classical techniques, to test the model further. From four isogenic lines of Drosophila melanogaster, four sets of recombinant extracted lines were constructed using standard balancer-chromosome techniques. The four parental lines and 53 recombinants were reared under controlled laboratory conditions and isolated as pairs for scoring daily fecundity and longevity. Even though the design is not optimal for estimating classical components of genetic variance, it afforded a uniquely direct test of the magnitude of environmental covariances, while giving a detailed genetic picture of part of the genome. There were clear differences among the recombinant series in the distribution of mean longevity and early fecundity. The genetic correlation between early fecundity (sum of egg production for the first five days posteclosion) and female longevity was significantly negative in only one of the recombinant series. When all lines were considered together, the phenotypic correlation between these traits was significantly negative (P < 0.02), while the broad-sense genetic correlation was –0.219 (P < 0.11). This result may be viewed as weakly consistent with the model of antagonistic pleiotropy, but other aspects of the data are at odds with the model.