Drosophila that have evolved postponed aging usually have reduced early reproduction. There are also negative genetic correlations between reproduction and survival characters in D. melanogaster. Similarly, Drosophila and other organisms that have postponed aging as a result of dietary restriction have reduced fertility. What is not clear is how nutrition and selection might interact with each other in the postponement of aging, given that both are affected by this type of trade-off. The central questions for this component project revolve around this interaction. (i) What are the effects of nutritional environment upon the genetic response to selection for postponed aging? (ii) Can genetic trade- offs between survival and reproduction be surmounted by nutritional manipulation? (iii) Can selection change the effects of dietary restriction upon aging and reproduction? Three main experiments are planned. (1) Selection for postponed aging with alternative nutritional regimes: high nutrition, low nutrition, and alternating high and low nutrition within generations. Differences in rates of response would indicate the relevance of dietary restriction to selection for postponed aging in laboratory systems, as well as test hypotheses concerning the evolutionary origins of the dietary restriction response. (2) Estimation of genetic correlations between early fecundity and starvation resistance (a factor that controls longevity) over four nutritional environments. This experiment would test the environmental dependence of the genetic correlation. (3) Selection for increased starvation resistance under varying nutritional regimes: high or low nutrition before starvation and high or low nutrition after starvation but before egg-laying. One of these selection regimes would favor the erosion of the normal dietary restriction response (high then low nutrition), while one would favor it (low then high nutrition). The experiment would test the degree to which the dietary restriction response can be genetically changed by selection. Experiments (s) and (3) might reveal conditions under which the trade-off between fecundity and starvation resistance is circumvented.
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