Meeting Abstract

P1.152  Wednesday, Jan. 4  Geographic variation in maternal effects across the breeding range of the tree swallow (Tachycineta bicolor) FORSMAN, A.M.*; PAITZ, R.T.; Cornell University; Illinois State University

During the process of egg-formation, hormones and immune compounds accumulate in the developing yolk and subsequently influence offspring development. Maternally derived steroids such as testosterone have been shown to influence offspring growth, behavior, and immune function while maternally derived antibodies (MAb’s) confer passive immunity to neonates with effects on growth and immune function. MAb’s neutralize many foreign antigens without the need for costly endogenous immune responses that would divert resources away from growth. Levels of these yolk substances vary with maternal experience, which has led to the hypothesis that females may utilize these substances to adjust offspring development to prevailing conditions. Understanding how levels of yolk steroids and MAb’s vary with maternal environment is critical to interpreting the evolutionary consequences of such maternal effects. In this study we investigated two potential factors that likely exert pressure upon these maternal effects: pace-of-life and antigenic diversity in the environment. We quantified levels of yolk androgens and antibodies (IgY) in eggs collected from across the breeding range of the North American tree swallow. The resulting latitudinal gradient captures fast pace-of-life birds in the north and slow paced birds in the south. We predicted that fast paced birds would lay eggs with higher levels of androgens and perhaps MAb’s than slow paced birds, but that MAb levels may also be influenced by antigenic pressure, which we assumed to be higher at lower latitudes. By investigating how levels of yolk androgens and MAb’s vary across an environmental gradient, we can begin to understand how these substances may be utilized to influence offspring development in a context-dependent manner.