University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2006 Avian Community Ecology: Patterns of Co-occurrence, Nestedness, and Morphology Michael David Collins University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Ecology and Evolutionary Biology Commons Recommended Citation Collins, Michael David, "Avian Community Ecology: Patterns of Co-occurrence, Nestedness, and Morphology. " PhD diss., University of Tennessee, 2006. https://trace.tennessee.edu/utk_graddiss/1927 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Michael David Collins entitled "Avian Community Ecology: Patterns of Co-occurrence, Nestedness, and Morphology." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Ecology and Evolutionary Biology. Daniel Simberloff, Christine R. B. Boake, Major Professor We have read this dissertation and recommend its acceptance: David Buehler, Sergey Gavrilets, Louis J. Gross Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a dissertation written by Michael David Collins entitled “Avian Community Ecology: Patterns of Co-occurrence, Nestedness, and Morphology.” I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Ecology and Evolutionary Biology. Daniel Simberloff Major Professor Christine R. B. Boake Department Head We have read this dissertation and recommend its acceptance: David Buehler Sergey Gavrilets Louis J. Gross Accepted for the Council: Anne Mayhew Vice Chancellor and Dean of Graduate Studies (Original signatures are on file with official student records.) Avian Community Ecology: Patterns of Co-occurrence, Nestedness, and Morphology A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Michael David Collins December 2006 To my mom and dad. I miss you, Mom. ii ACKNOWLEDGMENTS Many people have helped me at different stages of this work; without them, this project would not have been completed. My advisor, Dan Simberloff, provided guidance at all stages and showed immeasurable patience in allowing me the freedom and time to develop a dissertation of which I can be proud. My interactions with him have been academically and personally rewarding, and I extend to him my deepest gratitude. I am still impressed by his fairness, modesty, and objectivity. Discussions with colleagues have sharpened my thoughts. In particular, I thank Arijana Barun, Catherine Sheehy, Diego Vázquez, Howard Horne, Martin Nuñez, Monica Beals, Nate Sanders, Norris Muth, and Tad Fukami. My dissertation committee, Dan Simberloff, Dave Buehler, Lou Gross, and Sergey Gavrilets, provided cogent advice, criticism, and direction. Marc Cadotte, Martin Nuñez, Nate Sanders, Sean Gunter, and my committee critically read sections of the dissertation. Bruce Ralston, Dean Jue, Jeff Dahoda, Josh Calhoun, Matt Fitzpatrick, Steve Ahrens, Will Fontanez, and especially Jonathan Witcoski provided advice with GIS. During my time at the University of Tennessee, Phyllis Bice seemingly ran the department and constantly impressed me with her ability to solve problems that I had inadvertently created. I thank my family and friends for their unwavering support and enduring love. Dad, Steve, Jen, and Mark, Granny, Bart Kicklighter, Howard Horne, Norris Muth, Sean Gunter, and Tom Kennedy have enriched my life. And lastly, I thank my beautiful wife, Codruţa. I never could have done this without her. She and I are building a wonderful life together, and I am grateful for having found her. iii ABSTRACT A central tenet of the competition paradigm is that community structure is governed by deterministic rules. The competition paradigm pervades nearly all subdisciplines and extends to the broadest, deepest questions in ecology. To determine whether patterns of co-occurrence, nestedness, and morphology in avian communities are consistent with a competition hypothesis, I use null models to compare observed patterns to patterns expected in the absence of competition. I use presence-absence matrices of birds in three archipelagoes to test whether species exhibit exclusive distributions. Congeneric birds co-occur significantly less frequently than predicted in two archipelagoes, consistent with a competition hypothesis. However, when examined separately, most genera do not exhibit patterns that differ from random expectations. Furthermore, species differences in habitat preference and barriers to dispersal within archipelagoes are two alternate hypotheses that can explain many exclusive patterns and are supported by available data. Distributional evidence alone does not implicate competition. I argue that the range of conditions under which competition is likely to generate exclusive distributions across islands is narrow. Although nested patterns are viewed as the converse of competitive exclusion, meta- analyses of presence-absence matrices simultaneously support the ubiquity of exclusive distributions and indicate that most ecological systems are nested. I show why these apparently contradictory patterns are not mutually exclusive. Patterns of nestedness can result from multiple processes; without understanding mechanisms, nestedness analysis is unlikely to prove useful for conservation. I study algorithms that randomize presence-absence matrices. Two commonly used algorithms generate biased statistical distributions and should be abandoned. I test for community-wide character displacement in wing length and talon size among Accipiter hawks. I also assess whether subspecific variation in wing length is predictable from community composition. I find limited evidence of community-wide character displacement for wing length, but talon size, which relates directly to resource use, shows larger minimum and more equal size ratios than predicted. I find no evidence of competitively driven change in wing length. These findings demonstrate the importance of examining traits directly related to function. I cannot determine whether community-wide character displacement of talon size results from ecological character displacement, species assortment, or both. iv TABLE OF CONTENTS 1. A COMPARISON OF MATRIX RANDOMIZATION ALGORITHMS .................................1 INTRODUCTION.................................................................................................................1 METHODS............................................................................................................................3 RESULTS..............................................................................................................................5 DISCUSSION .......................................................................................................................7 2. AN EXAMINATION OF SPECIES CO-OCCURRENCE PATTERNS.................................10 INTRODUCTION...............................................................................................................11 METHODS..........................................................................................................................13 RESULTS............................................................................................................................15 DISCUSSION .....................................................................................................................17 3. PATTERNS AND CAUSES OF NESTEDNESS....................................................................27 INTRODUCTION...............................................................................................................28 METHODS..........................................................................................................................31 RESULTS............................................................................................................................35 DISCUSSION .....................................................................................................................36 4. MORPHOLOGICAL PATTERNS IN THE GENUS ACCIPITER .........................................44 INTRODUCTION...............................................................................................................44 METHODS..........................................................................................................................46 RESULTS............................................................................................................................49 DISCUSSION .....................................................................................................................50 LITERATURE CITED ..................................................................................................................53