Experimental evidence that oxidative stress influences reproductive decisions

Summary There is considerable interest of evolutionary ecologists in the proximate mechanisms that constrain life‐history variation. It is increasingly recognized that oxidative stress may be a prime physiological constraint on reproduction, but to the best of our knowledge, this has never been tested experimentally. To fill in this gap, we examined whether a specific and short‐term experimental increase of pre‐reproductive oxidative stress in females of a songbird (canary, Serinus canaria) would influence reproductive decisions (i.e. when and how many eggs to lay), and reproductive success (hatching and fledging success, number of hatchlings and of fledglings produced by each female), as compared to females whose oxidative stress levels were not manipulated. Our experimental reduction of glutathione, a key antioxidant, increased oxidative stress and affected reproductive decisions: treated females significantly delayed the start of egg laying and laid significantly smaller clutches. However, both hatching and fledging success and the number of hatchlings and of fledglings produced by each female were similar between control and treated females. Our results support the hypothesis that oxidative stress may be one proximate mechanism modulating key life‐history traits (such as the timing of laying and clutch size in birds) and therefore may act as a link between prevailing environmental conditions and fitness traits. Lay Summary