Social Environment, Hormones, and Ontogenetic Carry-Over Effects on Male Reproductive Phenotypes in a Polymorphic bird

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Male animals typically show considerable plasticity in the behavioral tactics and signals that they use to obtain mates. For example, in many bird populations, some males breed in bright plumage while others breed in relatively dull plumage. It is generally thought that plastic expression of sexual traits depends on both intrinsic (body condition) and extrinsic cues (social interactions), allowing males to adjust their investment in signals according to their quality and relative likelihood of mating success, and consequently that such traits honestly signal male quality to conspecifics. However, the mechanisms that translate these cues to male sexual traits, and thereby allow for plastic expression of sexual traits, are poorly understood. This research will examine the mechanisms of flexible expression of male reproductive phenotypes in the red-backed fairy wren (Malurus melanocephalus). In particular, this project will determine experimentally the effects of physical condition, social environment and stress on the hormones that affect male reproductive type. This work will combine both functional and mechanistic analyses, and will push the study of phenotypic plasticity and sexual signals in new directions. In addition, the research will explore carry-over effects of early life environment on male condition and reproductive type, a cutting-edge field of research emerging from the recent acknowledgement that early development can have important effects on adult traits. These results will have major implications for theoretical models of the evolution of sexual signals. This research also will contribute directly to the training of two graduate students and numerous undergraduates. Undergraduate training will include a novel internship program that will pair students from American universities with Australian students to conduct collaborative research. Thus, this project will involve undergraduates in all aspects of the research experience, from project design through publication, as well as giving them an enriching international experience.