Divergence of Drosophila species: Longevity and reproduction under different nutrient balances.

How nutrition impacts growth, reproduction and longevity is complex because relationships between these life events are difficult to disentangle. As a first step in sorting out these processes, we carried out a comparative analysis of related species of Drosophila with distinct feeding habits. In particular, we examined life spans and egg laying of two generalists and three specialists on diets with distinct protein-to-carbohydrate ratios. In contrast to the generalist D. melanogaster, adult males of two specialists, D. sechellia and D. elegans, lived longer on a protein-rich diet. These results and our previous studies collectively show that the diet to which larvae of each specialist species have adapted ensures a longer life span of adult males of that same species. We also found a species-specific sexual dimorphism of life span in the above two specialists regardless of the diets, which was in sharp contrast to D. melanogaster. In D. melanogaster, males lived longer than females, whereas females of D. sechellia and D. elegans were longer-lived than males, and those specialist females were exceedingly low in egg production, relative to the other species. We discuss our findings from perspectives of mechanisms, including a possible contribution of egg production to life span.