Dietary Restriction and Trade-offs Between Survival and Reproduction

进化出寿命更长的果蝇通常会减少早期繁殖。黑腹金丝猴的繁殖与生存特征(如耐饥性)之间也存在负相关。同样，果蝇和其他由于饮食限制而提高了存活率的生物也降低了生育率。目前尚不清楚的是，营养和选择如何在提高存活率方面相互作用，因为两者都受到这种权衡的影响。这个项目的中心问题围绕着这种相互作用：(I)生存和繁殖之间的基因权衡能否通过营养调控来克服？(2)选择能否改变限制饮食对生存和生殖的影响？计划进行两个主要实验。(1)四种营养环境下早期繁殖力和抗饥性(控制寿命的一个因素)之间的遗传相关性的估计。这项实验将检验遗传相关性的环境依赖性。(2)不同营养条件下提高抗饥性的选择：饥饿前营养水平高或低，饥饿后产蛋前营养水平高或低。这些选择制度中的一种将有利于削弱正常的饮食限制(高营养然后低营养)，而另一种则倾向于它(低营养然后高营养)。这项实验将测试通过选择可以从基因上改变饮食限制反应的程度。实验(1)和(2)可能揭示在繁殖力和耐饥性之间的权衡被规避的条件。

Drosophila that have evolved enhanced longevity usually have reduced early reproduction. There are also negative correlations between reproduction and survival characters (e.g. starvation resistance) in D. melanogaster. Similarly, Drosophila and other organisms that have enhanced survival 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 enhancement of survival, given that both are affected by this type of trade-off. The central questions for this project revolve around this interaction: (i) Can genetic trade-offs between survival and reproduction be surmounted by nutritional manipulation? (ii) Can selection change the effects of dietary restriction upon survival and reproduction? Two main experiments are planned. (1) 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 genetic correlation. (2) Selection for increased starvation resistance under varying nutritional regimes: high or low nutrition before starvation and high or low nutrition after starvation but before egglaying. One of these selection regimes would favor the erosion of the normal dietary restriction (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 (1) and (2) might reveal conditions under which trade-off between fecundity and starvation resistance is circumvented.