Within‐diet variation in rates of macronutrient consumption and reproduction does not accompany changes in lifespan in Drosophila melanogaster

다국어 초록 (Multilingual Abstract)

Interventions such as caloric or dietary restriction extend lifespan in organisms spanning from yeast to primates. Despite its positive influence on longevity, dietary restriction has been found to negatively affect reproduction. Many studies have reported negative correlations between lifespan and reproductive characteristics (such as mating rate, fecundity, reproductive period, and others). Such correlation gives the appearance of a resource‐based trade‐off between these two life‐history traits. Here, we have used nutritional geometry to confirm previous findings in flies that dietary macronutrient balance (protein‐to‐carbohydrate ratio, P:C) impacts both lifespan and reproduction, such that across a series of diets differing in P:C, maximum lifespan was observed at a lower P:C (1:8) than that which supported highest fecundity (1:1.5). We have then addressed the question whether variation among Drosophila melanogasterMeigen (Diptera: Drosophilidae) fruit flies in food intake and egg production within a single dietary treatment is negatively associated with within‐diet variation in lifespan, as might be expected under a resource‐based trade‐off. There was no such association between intake rate, egg production, and longevity. We noted that the smaller sample sizes and smaller inter‐individual variance apparent within — as compared to across — diet treatments may have weakened any signature of a trade‐off between lifespan and reproduction. Thus, we conclude that, whereas dietary macronutrient ratio is a primary determinant of both reproduction and longevity, neither eating less nor laying fewer eggs per se predicted lifespan. This supports the view that there is not a simple quantitative resource‐based trade‐off between lifespan and reproduction, but rather these represent life‐history traits with qualitatively different nutritional optima.
We used nutritional geometry to test possible relations between lifespan, rate of reproduction, and feeding in the model fruit fly Drosophila melanogaster (Diptera: Drosophilidae). We found no strong correlation between these traits. This means that among flies within a cohort that fed the same diet, higher reproduction or feeding rate is not associated with shorter lifespan.