Abstract
Understanding how diet affects reproduction and survival is a central aim in evolutionary biology. Although this relationship is likely to differ between the sexes, we lack data relating diet to male reproductive traits. One exception to this general pattern is Drosophila melanogaster, where male dietary intake was quantified using the CApillary FEeder (CAFE) method. However, CAFE feeding reduces D. melanogaster survival and reproduction, so may distort diet-fitness outcomes. Here, we use the Geometric Framework of Nutrition to create nutrient landscapes that map sex-specific relationships between protein, carbohydrate, lifespan and reproduction in D. melanogaster. Rather than creating landscapes with consumption data, we map traits onto the nutrient composition of forty agar-based diets, generating broad coverage of nutrient space. We find that male and female lifespan was maximised on low protein, high carbohydrate blends (~ 1P:15.9C). This nutrient ratio also maximised male reproductive rates, but females required more protein to maximise daily fecundity (1P:1.22C). These results are consistent with CAFE assay outcomes. However, the approach employed here improved female fitness relative to CAFE assays, while effects of agar versus CAFE feeding on male fitness traits depended on the nutrient composition of experimental diets. We suggest that informative nutrient landscapes can be made without measuring individual nutrient intake and that in many cases, this may be preferable to using the CAFE approach. The most appropriate method will depend on the question and species being studied, but the approach adopted here has the advantage of creating nutritional landscapes when dietary intake is hard to quantify.
Highlights
IntroductionDietary restriction (where individuals are fed less food but without causing malnutrition) extends lifespan but reduces fertility (Masoro 2005; Speakman and Mitchell 2011; Nakagawa et al 2012; Simons et al 2013)
In many species, dietary restriction extends lifespan but reduces fertility (Masoro 2005; Speakman and Mitchell 2011; Nakagawa et al 2012; Simons et al 2013)
For dietary carbohydrates the quadratic coefficient was negative for both sexes, meaning that there was a peak in lifespan on the nutritional landscape for this nutrient (Table 1; Fig. 1a, b)
Summary
Dietary restriction (where individuals are fed less food but without causing malnutrition) extends lifespan but reduces fertility (Masoro 2005; Speakman and Mitchell 2011; Nakagawa et al 2012; Simons et al 2013). It is better to invest in surviving to reproduce when environmental conditions improve. This idea probably oversimplifies the relationship between nutrition, lifespan and reproduction (Adler and Bonduriansky 2014), and is unlikely to apply to all species e.g. long-lived species that reproduce over multiple seasons (Shanley and Kirkwood 2006). Trade-offs involving reproduction may play a role in explaining why in some species, individuals live longer when they eat less (Moatt et al 2020; Zanco et al 2021)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
