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The Evolution of Forelimb Morphology and Flight Mode in Extant Birds A

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The Evolution of Forelimb Morphology and Flight Mode in Extant Birds A The Evolution of Forelimb Morphology and Flight Mode in Extant Birds A dissertation presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Erin L. R. Simons August 2009 © 2009 Erin L. R. Simons. All Rights Reserved. 2 This dissertation titled The Evolution of Forelimb Morphology and Flight Mode in Extant Birds by ERIN L. R. SIMONS has been approved for the Department of Biological Sciences and the College of Arts and Sciences by Patrick M. O'Connor Associate Professor of Anatomy Benjamin M. Ogles Dean, College of Arts and Sciences 3 ABSTRACT SIMONS, ERIN L. R., Ph.D., August 2009, Biological Sciences The Evolution of Forelimb Morphology and Flight Mode in Extant Birds (221 pp.) Director of Dissertation: Patrick M. O'Connor The research presented herein examines the morphology of the wing skeleton in the context of different flight behaviors in extant birds. Skeletal morphology was examined at several anatomical levels, including the whole bone, the cross-sectional geometry, and the microstructure. Ahistorical and historical analyses of whole bone morphology were conducted on densely-sampled pelecaniform and procellariiform birds. Results of these analyses indicated that the external morphology of the carpometacarpus, more than any other element, reflects differences in flight mode among pelecaniforms. In addition, elements of beam theory were used to estimate resistance to loading in the wing bones of fourteen species of pelecaniform. Patterns emerged that were clade-specific, as well as some characteristics that were flight mode specific. In all pelecaniforms examined, the carpometacarpus exhibited an elliptical shape optimized to resist bending loads in a dorsoventral direction. Moreover, birds that utilize flapping exhibited distal elements that were more elliptical than other flight modes, perhaps pertaining to the higher frequency of loading. Soaring birds exhibited wing elements with near-circular cross-sections and higher polar moments of area than in the flap and flap-gliding birds, suggesting shapes optimized to offer increased resistance to torsional loads. Congruent results between pelecaniform and procellariiform birds (two distantly related groups) indicate the presence of general trends in the structure and function of the avian wing 4 skeleton. In a separate analysis, bone microstructure of the forelimb elements of select pelecaniform, procellariiform, and falconiform taxa was examined. Data on the degree of primary vascular canal laminarity (i.e., the orientation of vascular canal networks) were collected and used to test a series of hypotheses related to the relationship between skeletal microstructure and inferred wing loading during flight. The dynamic soaring birds exhibited significantly lower laminarity in the wing elements than the flapping and static soaring birds, a result that may be explained by the difference in loading pattern due to overall wing shape variation among the groups. Finally, mechanical testing at the whole bone level was performed on individual wing elements to test predictions derived from whole-bone, cross-sectional geometric, and histological studies. These results revealed that variation in stiffness (Young’s modulus) exists both among wing elements within a given species and among species that utilize different primary flight modes. Specifically, the CMC and ulna were significantly stiffer than the humerus in all species, presumably to accommodate the loads transmitted through the flight feathers. In addition, the dynamic soaring albatross and continuous flapping cormorant exhibited stiffer wing elements than the static soaring pelican. In sum, differences detected in morphology and mechanical properties of avian wing elements do correspond with variation in primary flight mode and offer insight into the relationship between structure and function in the avian wing. Approved: _____________________________________________________________ Patrick M. O'Connor Associate Professor of Anatomy 5 This work is dedicated to my husband, Verne Simons 6 ACKNOWLEDGMENTS I would first like to extend a special thank you to my dissertation advisor, Patrick O’Connor, for his advice, insight, patience, and support. I wish to also thank my dissertation committee members, Audrone Biknevicius, Susan Williams, and Alycia Stigall, for providing valuable perspectives and encouragement. I would like to specifically thank Larry Witmer and Ryan Ridgely for assistance at the Ohio University microCT facility; Patrick O’Connor, Robert Hikida, Tobin Hieronymus, Susan Williams, and Andrew Lee for assistance with histological preparation and analysis; and Betty Sindelar and Susan Williams for assistance with mechanical testing. In addition, discussions with Audrone Biknevicius, Lisa Noelle Cooper, Joseph Daniel, David Dufeau, Joseph Eastman, Michael Habib, Jennifer Hancock, Jennifer Herman, Tobin Hieronymus, Casey Holliday, Dawn Holliday, Angela Horner, Michael Jorgensen, Andrew Lee, Emanuel de Margerie, Eric McElroy, Donald Miles, Molly Morris, Patrick O’Connor, Biren Patel, Steve Reilly, Willem Roosenburg, Christopher Ruff, Verne Simons, Betty Sindelar, Nancy Stevens, Alycia Stigall, Susan Williams, Larry Witmer, have greatly aided this research. I am indebted to the following curators and collection managers for access to specimens in their collections: P. Sweet and P. Hart (American Museum of Natural History), S. Rogers and B. Livezey (Carnegie Museum of Natural History), D. Willard (Field Museum of Natural History), J. Dean and S. Olson (National Museum of Natural History). 7 I also thank W. and B. Fox (Pelican Harbor Seabird Station, Miami, FL), C. Rehkemper and B. Zaun (Kauai National Wildlife Refuge Complex, HI), A. Freiman, S. Krause, M. Smith, and W. Smith (Sweetbriar Nature Center, NY), and Willem Roosenburg for avian specimens used during the course of this work. This research was supported by grants from the Ohio University Graduate Student Senate, the Ohio University Office of Research and Sponsored Programs (Student Enhancement Award), an AMNH Collection Study Grant from the Department of Ornithology, and the Ohio University College of Osteopathic Medicine (PMO). Finally, I wish to thank my husband, Verne Simons, for his constant support, encouragement, sense of humor, and incredible knowledge of how animals (and mechanical things) work. I am grateful to our families and friends for their endless encouragement. 8 TABLE OF CONTENTS Page Abstract ............................................................................................................................... 3 Acknowledgments............................................................................................................... 6 List of Tables .................................................................................................................... 12 List of Figures ................................................................................................................... 14 Preface ............................................................................................................................... 17 Literature Cited ............................................................................................................. 26 Chapter 1: Forelimb skeletal morphology and flight mode evolution in pelecaniform birds ........................................................................................................................................... 32 Abstract ......................................................................................................................... 32 Introduction ................................................................................................................... 33 Materials and Methods .................................................................................................. 35 Results ........................................................................................................................... 40 Allometric Analyses .................................................................................................. 40 Multivariate Analyses ............................................................................................... 41 Discussion ..................................................................................................................... 42 Allometric Aspects of the Pelecaniform Forelimb Skeleton .................................... 42 Multivariate Analyses: A Map to Flight Mode Evolution in Pelecaniforms ............ 44 Conclusion .................................................................................................................... 48 Literature Cited ............................................................................................................. 50 9 Chapter 2: Cross-sectional geometry of the forelimb skeleton and flight mode in pelecaniform birds ............................................................................................................ 63 Abstract ......................................................................................................................... 63 Introduction ................................................................................................................... 64 Materials and Methods .................................................................................................. 67 Results ..........................................................................................................................
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