Abstract:
The expression of life-history traits, such as lifespan or reproductive effort, is tightly
correlated with the amount and blend of macronutrients that individuals consume. In a
range of herbivorous insects, consuming high protein to carbohydrate ratios (P:C)
decreases lifespan but increases female fecundity. In other words, females face a resourcebased trade-off between lifespan and fecundity. Redox metabolism may help mediate
this trade-off, if oxidative damage is elevated by reproductive investment and if this
damage, in turn, reduces lifespan. Here, we test how diets varying in P:C ratio affect
oxidative damage and antioxidant protection in female and male of the marula fly, Ceratitis
cosyra (Diptera: Tephritidae). We use replicated lines that have been subjected to
experimental evolution and differ in their lifespan and reproductive scheduling. We predicted
that high fecundity would be associated with high oxidative damage and reduced
antioxidant defences, while longer lived flies would show reduced damage and elevated
antioxidant defences. However, higher levels of oxidative damage were observed in longlived control lines than selection lines, but only when fed the diet promoting lifespan. Flies
fed diets promoting female fecundity (1:4 and 1:2 P:C) suffered greater oxidative damage
to lipids than flies fed the best diet (0:1 P:C) for lifespan. Total antioxidant capacity was
not affected by the selection regime or nutrition. Our results reiterate the importance of
nutrition in affecting life-history traits, but suggest that in C. cosyra, reactive oxygen species
play a minimal role in mediating dietary trade-offs between lifespan and reproduction.
