Year of Award

2011

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Organismal Biology and Ecology

Department or School/College

Division of Biological Sciences

Committee Chair

Creagh W. Breuner

Commitee Members

Douglas J. Emlen, Lila Fishman, Thomas E. Martin, Carol M. Vleck

Keywords

Corticosterone, Fitness, Individual Quality, Life History Tradeoffs, Parental Behavior, Stress

Abstract

Organisms cannot simultaneously maximize their investment in survival and reproductive success, thus these traits are said to trade off against one another. The physiological mechanisms that help guide these investment decisions are not fully understood. Stress-induced corticosterone is a strong candidate mechanism, because it is thought to promote survival-oriented behavior and physiology at the expense of non-critical functions such as reproduction. In this dissertation, I studied multiple components of corticosterone physiology (baseline corticosterone and stress-induced corticosterone) in several species of passerine birds to address this question from a variety of angels. I first provide direct support for corticosterone playing a role in the reproduction-survival tradeoff. Stress-induced measures of corticosterone predicted greater survival and lower reproductive performance. Baseline corticosterone, however, appears to reflect quality, with greater baseline levels associated with greater survival and reproduction. I then explore the relationship between corticosterone and reproduction at a finer scale, using both correlative and experimental approaches. Individual variation in corticosterone was negatively associated with both brooding behavior and offspring feeding rate, but experimental manipulation of corticosterone in the latter study had no effect. And finally, I evaluated the relationship between environment and endogenous corticosterone levels, finding no support for any relationship between the two. Altogether these results show that corticosterone is closely tied to survival and reproduction and should be considered when evaluating mechanisms of investment in fitness.

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© Copyright 2011 Stephen Harold Patterson