Cost of reproduction in the Queensland fruit fly: Y-model vs. lethal protein hypothesis

The trade-off between lifespan and reproduction is commonly explained by differential allocation of limited resources. Recent research has shown that the ratio of protein to carbohydrate (P:C) of a fly's diet mediates the lifespan/reproduction trade-off, with higher P:C diets increasing egg production but decreasing lifespan. To test if this P:C effect is due to changing allocation strategies (Y-model hypothesis) or detrimental effects of protein ingestion on lifespan (lethal protein hypothesis), we measured lifespan and egg production in Queensland fruit flies varying in reproductive status (mated, virgin, and sterilized females, virgin males) that were fed one of 18 diets varying in protein and carbohydrate amounts. The Y-model predicts that for sterilized females and for males, which require little protein for reproduction, there will be no effect of P:C ratio on lifespan; the lethal protein hypothesis predicts that the effect of P:C ratio should be similar in all groups. In support ...