The Nature of Beauty: How Environmental Conditions Impact Sexual Selection in the Zebra Finch
- Author(s): Wilson, Kerianne Murphy
- Advisor(s): Burley, Nancy T
- et al.
Development and reproduction are life history stages during which the demand for resources is especially high, so individuals are expected to be particularly vulnerable to environmental conditions during these times. Thus, the way in which an individual allocates resources to different life functions during these two life stages should be meaningful in shaping natural and sexual selection. In a series of breeding experiments, my research examined the effects of diet quality on development and reproductive patterns of zebra finches. I focused on the following questions: (1) How does developmental diet influence the adult expression of male secondary sexual traits and male reproductive success via social mates vs. extra-pair partners? (2) How do females adjust reproductive allocation in response to the diet history of their social and extra-pair mates? (3) How do early diet and breeding diet jointly influence parental investment patterns and reproductive success of social mates during the incubation phase? To address these questions, I manipulated zebra finch developmental and/or breeding diet quality and tracked founders and offspring from multiple breeding colonies over three successive generations. Throughout the birds’ development and reproduction, I quantified traits and behaviors expected to contribute to survival and fitness. The first chapter of my thesis found that males raised under high-quality nutritional conditions had higher adult expression of visual, but not acoustic, secondary sexual traits as well as higher fitness via production of sons and extra-pair paternity. Chapter 2 demonstrates that females differentially allocate resources in response to male quality (both based on a natal diet manipulation and extra-pair success) and to extra-pair offspring, and that females obtained direct fitness benefits from pairing with attractive males. Results from Chapter 3 indicate that birds exposed to a high-quality diet during development and a low-quality diet during reproduction struggle to invest in both reproduction and somatic maintenance during the incubation phase, suggesting this diet history combination may be detrimental to survival and reproduction.