Data from: Drosophila melanogaster larvae make nutritional choices that minimize developmental time

Organisms from slime moulds to humans carefully regulate their
macronutrient intake to optimize a wide range of life history characters
including survival, stress resistance, and reproductive success. However,
life history characters often differ in their response to nutrition,
forcing organisms to make foraging decisions while balancing the
trade-offs between these effects. To date, we have a limited understanding
of how the nutritional environment shapes the relationship between life
history characters and foraging decisions. To gain insight into the
problem, we used a geometric framework for nutrition to assess how the
protein and carbohydrate content of the larval diet affected key life
history traits in the fruit fly, Drosophila melanogaster. In no-choice
assays, survival from egg to pupae, female and male body size, and
ovariole number – a proxy for female fecundity – were maximized at the
highest protein to carbohydrate (P:C) ratio (1.5:1). In contrast,
development time was minimized at intermediate P:C ratios, around 1:2.
Next, we subjected larvae to two-choice tests to determine how they
regulated their protein and carbohydrate intake in relation to these life
history traits. Our results show that larvae targeted their consumption to
P:C ratios that minimized development time. Finally, we examined whether
adult females also chose to lay their eggs in the P:C ratios that
minimized developmental time. Using a three-choice assay, we found that
adult females preferentially laid their eggs in food P:C ratios that were
suboptimal for all larval life history traits. Our results demonstrate
that D. melanogaster larvae make foraging decisions that trade-off
developmental time with body size, ovariole number, and survival. In
addition, adult females make oviposition decisions that do not appear to
benefit the larvae. We propose that these decisions may reflect the living
nature of the larval nutritional environment in rotting fruit. These
studies illustrate the interaction between the nutritional environment,
life history traits, and foraging choices in D. melanogaster, and lend
insight into the ecology of their foraging decisions.