Revisiting the link between breeding effort and oxidative balance through field evaluation of two sympatric sibling insect species

The idea that oxidative stress could be a major force governing evolutionary trade-offs has recently been challenged by experimental approaches in laboratory conditions triggering extensive debates centered on theoretical and methodological issues. Here, we revisited the link between oxidative stress and reproduction by measuring multiple antioxidant and oxidative damages in wild-caught females of two sibling weevil species (Curculio elephas, C. glandium). The strength of our study arises from: (1) studied species are sympatric and exploit similar resource but display contrasting reproductive strategies and (2) individuals were sampled throughout adult life so as to relate oxidative status to breeding effort. We found that the short-lived C. elephas sacrifices red-ox homeostasis for immediate reproduction upon emergence as characterized by low antioxidant defenses and elevated oxidative damage. Comparatively, C. glandium massively invests in antioxidant and maintains low oxidative damage, which may contribute to their extended pre-reproductive period. Intriguingly, we also reveal, for the first time in a field study, an unexpected reactivation of antioxidant defenses with the onset of reproduction. Our results thus support the existence of a strong but complex relationship between oxidative stress and life history evolution and highlight the need for a finer-scale picture of antioxidant strategies.