Plumage Coloration and Morphology in Chiroxiphia Manakins
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PLUMAGE COLORATION AND MORPHOLOGY IN CHIROXIPHIA MANAKINS: INTERACTING EFFECTS OF NATURAL AND SEXUAL SELECTION Except where reference is made to the work of others, the work described in this dissertation is my own or was done in collaboration with my advisory committee. This dissertation does not include proprietary or classified information. _________________________________________ Stéphanie M. Doucet Certificate of Approval: _____________________ _____________________ F. Stephen Dobson Geoffrey E. Hill, Chair Professor Schamagel Professor Biological Sciences Biological Sciences ______________________ ______________________ Craig Guyer Stephen L. McFarland Professor Acting Dean Biological Sciences Graduate School PLUMAGE COLORATION AND MORPHOLOGY IN CHIROXIPHIA MANAKINS: INTERACTING EFFECTS OF NATURAL AND SEXUAL SELECTION Stéphanie M. Doucet A Dissertation Submitted to the Graduate Faculty of Auburn University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Auburn, Alabama May 11, 2006 PLUMAGE COLORATION AND MORPHOLOGY IN CHIROXIPHIA MANAKINS: INTERACTING EFFECTS OF NATURAL AND SEXUAL SELECTION Stéphanie M. Doucet Permission is granted to Auburn University to make copies of this dissertation at its discretion, upon request of individuals or institutions and at their expense. The author reserves all publication rights. ____________________________________ Signature of Author ____________________________________ Date of Graduation iii DISSERTATION ABSTRACT PLUMAGE COLORATION AND MORPHOLOGY IN CHIROXIPHIA MANAKINS: INTERACTING EFFECTS OF NATURAL AND SEXUAL SELECTION Stéphanie M. Doucet Doctor of Philosophy, May 11, 2006 (M.S. Queen’s University, 2002) (B.S. Queen’s University, 2000) 231 Typed Pages Directed by Dr. Geoffrey E. Hill I examined how natural and sexual selection may have influenced the morphology and coloration of Chiroxiphia manakins (Aves: Pipridae). In the first chapter, I investigated age– and sex–related patterns of plumage coloration and molt timing in long–tailed manakins, C. linearis. I examined how plumage coloration changed with age in males and females based on 1315 mist net captures in northwestern Costa Rica and examined molt patterns in an additional 585 museum specimens. Males followed a remarkably age–specific pattern of plumage maturation before attaining definitive adult plumage in their fifth year. Some females developed male–like plumage characteristics as they aged, but not reliably so. Although molt–breeding overlap occurred at the population level, few individuals molted while breeding. In the second chapter, I examined the explanatory power of natural and sexual selection hypotheses in explaining patterns of iv sexual dimorphism in Chiroxphia manakins. I measured six morphological traits in 361 wild C. linearis and a subset of these traits in 872 museum specimens of Chiroxphia manakins. My findings were consistent with both sexual selection and natural selection hypotheses, suggesting that both mechanisms have strongly influenced the evolution of sexual dimorphism in this group. In the third chapter, I investigated how the perceptual environment influences the conspicuousness of plumage displays in long–tailed manakins. I measured the reflectance of 62 males and 59 females, the reflectance of the background vegetation, and the irradiance of light at display perches. Male manakins were highly conspicuous against the visual background, whereas females were relatively cryptic. Males did not appear to adjust the location or timing of their displays to take advantage of particular light conditions but rather displayed in the most common light environment of forest shade. Displays performed in forest shade may optimize the short–distance conspicuousness of male plumage ornaments while minimizing the long–distance conspicuousness of male ornaments and the short– and long–distance conspicuousness of female plumage patterns. In the fourth chapter, I evaluated the degree to which the color of study skins is representative of coloration in wild birds. I measured the plumage reflectance of 58 wild and 55 museum specimens of long–tailed manakins. I found significant differences in color between museum specimens and wild birds, and the degree of difference depended on the coloration mechanism. Potential sources of these differences include the specimen preparation process, the age of specimens, and geographic variation. Although caution is warranted for some types of studies, most differences were relatively subtle, justifying the use of museum specimens to assess color in many instances. v ACKNOWLEDGEMENTS I must first acknowledge the contributions of my co–authors for the various chapters of this dissertation. Order of authorship is as follows: Chapter 1: S. M. Doucet, D. B. McDonald, M. S. Foster, and R. P. Clay; Chapter 2: S. M. Doucet, F. Hertel, and G. E. Hill, Chapter 3: S. M. Doucet and G. E. Hill; Chapter 4; S. M. Doucet and G. E. Hill. I thank all of these colleagues for their direct contributions to particular chapters and for indirect contributions in the form of advice, observations, support, and encouragement. The contributions of many other individuals, institutions, and funding agencies are acknowledged in each chapter. Dr. Geoffrey Hill has been an outstanding advisor and mentor. I am grateful for the academic freedom he provided. He taught me much about the ins and outs of academia. His drive, boundless enthusiasm, and ability to expertly juggle his academic and personal lives are admirable. He leads by example and leaves most of us panting in his wake. I am also grateful to the members of my advisory committee, Dr. Steve Dobson and Dr. Craig Guyer, for their guidance, editorial suggestions, statistical advice, and encouragement. My external reader, Dr. Henry Fadamiro, provided helpful feedback and suggestions on the dissertation. I also benefited greatly from the advice and support of other colleagues, most notably Dr. Herman Mays, Dr. Dan Mennill, Dr. Bob Montgomerie, Dr. Laurene vi Ratcliffe, and Dr. Matthew Shawkey. My many labmates over the years were a constant source of ideas, support, amusement, and friendship, and I offer my sincerest thanks. My friends and family have contributed more to this dissertation than they could possibly imagine. My extended family cheered me on. My friends were a most welcome diversion, commiserating or celebrating as warranted by the occasion. Sandi, Paul, and Sally were tremendous sources of encouragement and inspiration. My brother Vernon was understanding and supportive. My mother and father, Mercia and Conrad, long ago presented the world as a place full of opportunities for me. They glossed over my mistakes and sang my praises. They made sacrifices so that I could achieve what hadn’t been a possibility for them. I will be forever grateful. I owe my greatest debt of gratitude to my husband, Dan. His contributions are more numerous and of greater importance than can be conveyed here. He has been involved with my dissertation project from the very beginning, first serving as a sounding board for my ideas, then helping with many parts of data collection, and finally reading several manuscript drafts. His hard work, dedication, and many successes were a daily source of inspiration. He, too, made some sacrifices and compromises which enabled me to pursue my work. I am so very thankful for all of these things. I am most grateful, however, for his unwavering love and support. His encouragement and ability to convey the bigger picture helped me through the rough spots, and he was always my biggest fan when things were going well. I don’t know how I would have managed without him. vii Style manual of journal used: The American Naturalist Computer Software Used: Microsoft Word, Microsoft Exel, JMP, EndNote viii TABLE OF CONTENTS LIST OF TABLES ......................................................................................................... xi LIST OF FIGURES......................................................................................................xiii CHAPTER 1. PLUMAGE DEVELOPMENT AND MOLT IN LONG–TAILED MANAKINS: VARIATION ACCORDING TO SEX AND AGE ................................... 1 Abstract.......................................................................................................................2 Introduction.................................................................................................................3 Methods ......................................................................................................................5 Results ........................................................................................................................8 Discussion.................................................................................................................16 Acknowledgements ...................................................................................................26 Literature Cited .........................................................................................................28 Figure Captions.........................................................................................................35 CHAPTER 2. COMPLEX PATTERNS OF SEXUAL DIMORPHISM IN CHIROXPHIA MANAKINS: INTERACTING EFFECTS OF NATURAL AND SEXUAL SELECTION?............................................................................................... 39 Abstract.....................................................................................................................40