Sexual Selection in the American Goldfinch (Spinus tristis): Context-Dependent Variation in Female Preference Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Donella S. Bolen, M.S. Graduate Program in Evolution, Ecology, and Organismal Biology The Ohio State University 2019 Dissertation Committee: Ian M. Hamilton, Advisor J. Andrew Roberts, Advisor Jacqueline Augustine 1 Copyrighted by Donella S. Bolen 2019 2 Abstract Females can vary in their mate choice decisions and this variability can play a key role in evolution by sexual selection. Variability in female preferences can affect the intensity and direction of selection on male sexual traits, as well as explain variation in male reproductive success. I looked at how consistency of female preference can vary for a male sexual trait, song length, and then examined context-dependent situations that may contribute to variation in female preferences. In Chapter 2, I assessed repeatability – a measure of among-individual variation – in preference for male song length in female American goldfinches (Spinus tristis). I found no repeatability in preference for song length but did find an overall preference for shorter songs. I suggest that context, including the social environment, may be important in altering the expression of female preferences. In Chapter 3, I assessed how the choices of other females influence female preference. Mate choice copying, in which female preference for a male increases if he has been observed with other females, has been observed in several non-monogamous birds. However, it is unclear whether mate choice copying occurs in socially monogamous species where there are direct benefits from choosing an unmated male. I found evidence for mate choice copying and suggest that copying occurs when choosing extrapair mates. In Chapter 4, I examine how social relationships among females influence copying. A female may be more likely to copy another female if they are ii familiar with one another due to shared environments and experiences. I found that females are more likely to copy familiar rather than unfamiliar females, which has not been shown in this context. The latter two chapters show that social context is a source of variation that can cause a female to alter her preferences. This suggests an important potential role of female-female social relationships on male reproductive success and the evolution of male characteristics. iii Acknowledgments I wish to thank, first and foremost, my advisors, Ian Hamilton and Andy Roberts, without whom this never could have happened. Their patience, guidance, and generosity are something for which I will always be grateful. I also wish to thank my other committee member, Jackie Augustine, for her helpful comments and advice. I thank the animal behavior joint lab group at OSU for their feedback on early versions of this manuscript. Thanks to Sandy Shew, Barb Shardy, Andy Jones, Keith Tarvin, and Doug Nelson and the Borror Laboratory of Bioacoustics for assisting with a variety of technical, equipment, and design issues. Heather Devine, Anne Sabol, Kirsten Cadmen, Craig Miller, Samantha McGlone, Sarah Hamza, Molly Bobich, Brooke Nerderman, and Shannon Kelley were invaluable in helping to care for captive birds. Katelyn Scott deserves special thanks as my research assistant. Thanks also to Chadwick Arboretum North, Waterman Agriculture and Natural Resources Laboratory Complex, the Wilma H. Schiermeier Olentangy River Wetland Research Park, Highbanks Metro Park, and The Dawes Arboretum for access to their properties. The Macaulay Library at the Cornell Lab of Ornithology and the Borror Laboratory of Bioacoustics provided acoustic recordings. Taxidermy services provided by McNamara’s Taxidermy Studio (Lima, Ohio). This project was supported by funding from D. Nelson and the Borror Laboratory of Bioacoustics, and The Ohio State University Alumni Grants for Graduate Research iv and Scholarship. Finally, I wish to thank Steve Chordas and Wayne Babcock for always being encouraging and supportive. v Vita 1993 …………………………………B.S. Accounting, The University of Akron 2002 …………………………………B.S. Zoology, The University of Akron 2003 – 2004 ………………………...Wild Animal Keeper, Akron Zoological Park 2006 – 2009 ………………………...Graduate Assistant, Biology Department, John Carroll University 2011 ………………………………...M.S. Biology, John Carroll University 2009 – present ………………………Graduate Assistant, Department of Evolution, Ecology, and Organismal Biology and the Center for Life Sciences Education, The Ohio State University Fields of Study Major Field: Evolution, Ecology, and Organismal Biology vi Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita ..................................................................................................................................... vi List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x Chapter 1. INTRODUCTION ............................................................................................. 1 Chapter 2. LACK OF REPEATABILITY OF FEMALE PREFERENCE FOR SONG LENGTH IN THE AMERICAN GOLDFINCH (SPINUS TRISTIS)............................... 10 ABSTRACT .................................................................................................................. 10 INTRODUCTION ........................................................................................................ 11 METHODS ................................................................................................................... 15 RESULTS ..................................................................................................................... 26 DISCUSSION ............................................................................................................... 31 Chapter 3. EVIDENCE FOR MATE CHOICE COPYING IN A SOCIALLY MONOGAMOUS SPECIES, THE AMERICAN GOLDFINCH (SPINUS TRISTIS) ..... 37 ABSTRACT .................................................................................................................. 37 INTRODUCTION ........................................................................................................ 38 METHODS ................................................................................................................... 41 RESULTS ..................................................................................................................... 48 DISCUSSION ............................................................................................................... 54 SUPPLEMENTAL MATERIAL .................................................................................. 59 Chapter 4. FAMILIARITY AMONG FEMALES INCREASES MATE CHOICE COPYING IN THE AMERICAN GOLDFINCH (SPINUS TRISTIS) ............................. 62 ABSTRACT .................................................................................................................. 62 INTRODUCTION ........................................................................................................ 63 METHODS ................................................................................................................... 67 vii RESULTS ..................................................................................................................... 74 DISCUSSION ............................................................................................................... 78 SUPPLEMENTAL MATERIAL .................................................................................. 81 Chapter 5. CONCLUSION ............................................................................................... 83 LITERATURE CITED ..................................................................................................... 89 viii List of Tables Table 1 Single Measures Intraclass Correlation Coefficients (ICC) to examine repeatability of female choice for short or long song and repeatability of time spent in the center of the arena. ............................................................................................................ 27 Table 2 Estimated marginal means and 95% Wald confidence intervals from the main effects of the Generalized Estimating Equation. Means represent the probability of choosing the long song...................................................................................................... 30 Table 3 Model effects in the Generalized Estimating Equation used to examine the effects of female preference for short or long song. Subject variable is the individual female and within-subject variable is trial. .......................................................................................... 30 Table 4 Generalized Estimating Equation to examine the effects of treatment, bird age, and trial order on the difference in the proportion of time spent with the less preferred male over time spent with either male from the pre-test phase to the post-test phase. Subject variable is the individual female and within-subject variable