Life-history traits are often involved in trade-offs whose outcome would depend on the availability of resources but also on the state of specific molecular signals. Early conditions can influence trade-offs and program the phenotype throughout the lifetime, with oxidative stress likely involved in many taxa. Here we address the potential regulatory role of a single intracellular antioxidant in life-history trade-offs. Blood glutathione levels were reduced in a large sample of birds (zebra finch Taeniopygia guttata) during development using the synthesis inhibitor buthionine sulfoximine (BSO). Results revealed several modifications in the adult phenotype. BSO-treated nestlings showed lower glutathione and plasma antioxidant levels. In adulthood, BSO birds endured greater oxidative damage in erythrocytes but stronger expression of a sexual signal. Moreover, adult BSO females also showed weaker resistance to oxidative stress but were heavier and showed better body condition. Results suggest that low glutathione values during growth favor the investment in traits that should improve fitness returns, probably in the form of early reproduction. Higher oxidative stress in adulthood may be endured if this cost is paid later in life. Either the presence of specific signaling mechanisms or the indirect effect of increased oxidative stress can explain our findings.

Romero-Haro & Alonso-Alvarez 10-3-2014 repositoryExcel file containing the variables used in the analyses with descriptions of each variable as comments inserted in the cell that defines each variable name.Romero-Haro & Alonso-Alvarez 10-3-2014 REPEATED repositoryExcel data file containing body mass and tarsus lengths of the birds in the study from the nestling age to adulthood. The file was created to perform the analyses by means of repeated measures mixed models, that is, including the individual identity as a random factor.