Larval protein restriction interacts with adult diet to increase fitness
in an outbred multiparent population.
Abstract
Developmental conditions including temperature, diet, and parasites can
shape adult fitness phenotypes in many species. Studies typically focus
on the additive effects of early-life and adult life conditions on life
history response in the context of competing models of developmental
plasticity (i.e. environmental matching and silver spoon). These models
continue to yield mixed results in the same or different species. Here,
we characterize interaction effects of larval vs adult diet on lifespan
and fecundity in a high diversity outbred population of Drosophila
melanogaster. We compare fitness proxies of matched vs mismatched
early-to-late nutritional conditions differing in protein content. Diet
interactions significantly affected both traits, albeit differently. We
find no consistent evidence for either model. Rather, several patterns
emerged including age and sex effects, survival differences in the
post-median life phase, regime-specific timing of peak fecundity, and
substantial fecundities in older post-median flies. We find that mild
protein restriction increases both maximum lifespan of males and female
lifetime fecundity. Surprisingly, lower adult protein delayed egg-laying
by about 2 weeks, compared to treatments with higher protein in adult
diet. This effect was particularly evident in treatments involving
protein-restricted developmental diets. Our results highlight the need
for assessing patterns of response over the course of life which can
potentially reveal more subtle interacting processes compared to
cross-sectional measurements. In addressing the impacts of environmental
change in natural systems, it will be necessary to consider nuanced
approaches that account for both, additive and interaction effects in
diverse genetic backgrounds.