Meeting Abstract
Females are thought to choose mates based on the size or color of male ornaments because they are indicators of male quality. By choosing more ornamented males, females could potentially gain heritable benefits for their offspring, such as superior genes for parasite resistance. These genes might not only reduce the risk of infection, but also the oxidative damage caused during prolonged immune responses. In our study we tested the hypothesis that ornaments are honest indicators of the ability of males to manage oxidative stress. In our study population of common yellowthroats (Geothlypis trichas), females prefer to mate with males with larger black facial masks, and mask size is positively correlated with antibody production (IgG) and variation at the major histocompatibility complex (MHC). We induced an immune response in males with an injection of a bacterial membrane component and measured harmful pro-oxidants and protective antioxidants before and 24 hours after injection. Although immune response did not increase oxidative stress (change in oxidative stress was the same between treated and untreated individuals), males with larger masks experienced a larger decrease in glutathione, an important intracellular antioxidant, and a larger increase in reactive oxygen metabolites, an early marker of oxidative damage. Change in total antioxidant capacity (TAC) in the plasma was not related to mask size or treatment group. It is possible that exposure to a stressful environment, such as 24 hours in captivity, may have caused the change in oxidative stress in males with larger masks. In the future, we will investigate ornament size and additional indicators of stress.
