Title of My Thesis
Total Page：16
File Type：pdf, Size：1020Kb
UC San Diego UC San Diego Electronic Theses and Dissertations Title The broader ecological effects of species invasion on protection mutualisms / Permalink https://escholarship.org/uc/item/82p479kq Author LeVan, Katherine Elizabeth Publication Date 2013 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA, SAN DIEGO The broader ecological effects of species invasion on protection mutualisms A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Biology by Katherine Elizabeth LeVan Committee in charge: Professor David A. Holway, Chair Professor Elsa Cleland Professor Micky D. Eubanks Professor Phil Hastings Professor James Nieh 2013 Copyright Katherine Elizabeth LeVan, 2013 All rights reserved This dissertation of Katherine Elizabeth LeVan is approved, and it is acceptable in quality and form for publication on microfilm and electronically: ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Chair University of California, San Diego 2013 iii DEDICATION To my parents, family, and friends that provided me emotional support without which this dissertation would have been exceedingly less likely to have been completed. In some sense, this is as much your accomplishment as mine. Thanks guys. iv TABLE OF CONTENTS Signature Page…..…………………………………………………………………………....... iii Dedication……………………………………………………………………………………...... iv Table of Contents…………….………………………………………………………………..... v List of Figures…………………………………………………………………........................ vii List of Tables………………………………………………………………………………….... viii Acknowledgements…………………………………………………………………………...... ix Vita……………………………………………...……………………………………………..... xi Abstract of the Dissertation……..……………………………………………………….……. xii Introduction of the Dissertation.………………………………………………………….......... 1 References...............…………………………………………………..…....…............ 6 Floral visitation by the Argentine ant reduces pollinator visitation and seed set in the coast barrel cactus, Ferocactus viridescens ………………………………….……………. 12 Abstract…………………………………………………………………..…....………. 12 Introduction..……………………………………………………………..…....………. 12 Methods.......……………………………………………………………..…....………. 13 Results........……………………………………………………………..…....………. 15 Discussion...……………………………………………………………..…....………. 18 Acknowledgements……………………………………………………..…....………. 19 References............……………………………………………………..…....………. 19 Acknowledgements……………………………………………………..…....………. 20 Argentine ant invasion reduces mutualist guild diversity and food web complexity…… 21 Abstract…………………………………………………………………..…....………. 21 Introduction..……………………………………………………………..…....………. 22 v Methods.......……………………………………………………………..…....………. 26 Results........……………………………………………………………..…....………. 29 Discussion...……………………………………………………………..…....………. 32 Acknowledgements……………………………………………………..…....………. 35 References............……………………………………………………..…....………. 36 Ant-aphid mutualism increases floral visitation by ants and reduces plant fitness via decreased pollinator visitation …………………………………………………………….… 47 Abstract…………………………………………………………………..…....………. 47 Introduction..……………………………………………………………..…....………. 48 Methods.......……………………………………………………………..…....………. 51 Results........……………………………………………………………..…....………. 55 Discussion...……………………………………………………………..…....………. 58 Acknowledgements……………………………………………………..…....………. 61 References............……………………………………………………..…....………. 62 An experimental test of how mutualisms between the Argentine ant and cotton aphid structure arthropod food webs in cotton................................…………………………...... 73 Abstract…………………………………………………………………..…....………. 73 Introduction..……………………………………………………………..…....………. 74 Methods.......……………………………………………………………..…....………. 75 Results........……………………………………………………………..…....………. 78 Discussion...……………………………………………………………..…....………. 81 Acknowledgements……………………………………………………..…....………. 84 References............……………………………………………………..…....………. 84 vi LIST OF FIGURES Figure 1.1. Argentine ant vs. native ant abundance in flowers………………………….. 16 Figure 1.2. A test of ant aversion toward petal compounds………………………..…..... 16 Figure 1.3. Number and duration of cactus bee visits………………………….……….... 17 Figure 1.4. Cactus reproduction versus ant species identity………….……………...…. 17 Figure 2.1. A map of 6 paired riparian sites…………………………………………..….... 43 Figure 2.2. Aphid richness versus ant invasion status………………………………….... 43 Figure 2.3. Interaction networks for invaded and uninvaded sites...……………….….... 44 Figure 2.4. Ant:aphid ratio decreases with aggregation size……………………….….... 45 Figure 2.5. Measures of food web complexity change with ant richness………….….... 46 Figure 3.1. Estimated cotton aphid abundance in three years………………………….. 69 Figure 3.2. Effect of aphids on ant abundance in leaves and flowers………………….. 70 Figure 3.3. Effect of ant floral visitation on pollinator and bee visit duration………….... 71 Figure 3.4. Effect of aphid abundance on seed production……………………………... 72 Figure 4.1. Mean time-averaged aphid and ant abundance on cotton.......……………. 93 Figure 4.2. Effect of aphid density treatment on morphospecies composition............... 94 Figure 4.3. Effect of aphid density treatment on linkage within food webs…………….. 95 Figure 4.4. Effect of ant presence on generalist and specialist predator behavior toward aphid prey...................................................................................................……………. 96 Figure 4.5. Effect of aphid-density treatment on Lepidotera abundance and feeding… 97 vii LIST OF TABLES Table 1.1: Reproductive traits of coast barrel cacti (Ferocactus viridescens).………..... 14 Table 1.2: The effects of ant species identity and year on plant reproduction................ 17 Table 2.1: Species distributions of ants, aphids, and wasps……………………….…….. 42 Table 3.1: Details of the experimental regime that differed between years……………. 67 Table 3.2: Results of GLM analyzing the effect of aphid abundance on plant fitness… 68 Table 4.1: Identities and abundance of species in the study…………………………..…. 88 viii ACKNOWLEDGEMENTS The support that I received from mentors, colleagues, and family were integral to the success of this dissertation. Without their assistance and guidance, this thesis would not have been possible. Of course, I must acknowledge Professor David Holway for his support as the chair of my committee. Through multiple drafts, his guidance has proved to be invaluable. However, an advisor is only one of the many people that are a support network. My committee has also provided expertise and guidance on experimental design and statistical analysis, without which, this dissertation would have been the poorer. Thus, I gratefully acknowledge the assistance received from Elsa Cleland, James Nieh, Phil Hastings, and Micky Eubanks. Discussions with this group of committee members have enriched my scientific development and this project. Beyond the official assistance that a committee provides, I also benefited from conversations and advice from members within the lab and grad community. For long talks about science, crazy news stories, and international differences between Canada and the US, I have to thank Erin Wilson, Elinor Lichtenberg, James Hung, Chris Kopp, Akana Noto, Ellen Esch and Celia Symons. The success of my research was improved by access to field sites, for which Isabelle Kay and Pablo Bryant were extremely helpful. Finally, I must thank my family and close friends who endured a lot of late night conversations and supported me emotionally through the roller coaster that is a PhD thesis. Their encouragement has been priceless to me and has significantly (p < 0.05) contributed to me completing the dissertation. For that I will always be grateful. In particular, I want to say that Meghan F. Hogan and Peter C. St. John are probably the best two people in the world and I hope that they both know that their support was of great value to me in this difficult process. ix Chapter 1, in full, is a reprint of an article as it appears in Oecologia. LeVan, KE, KJ Hung, KR McCann, JT Ludka and DA Holway. 2013. “Floral visitation by the Argentine ant reduces pollinator visitation and seed set in the coast barrel cactus, Ferocactus viridescens.” The dissertation author was the primary investigator and author of this manuscript. Chapter 2, in part, has been submitted for publication as it may appear in Molecular Ecology. LeVan, KE and DA Holway. “Argentine ant invasion reduces mutualist guild diversity and food web complexity.” The dissertation author was the primary investigator and author of this paper. Chapter 3, in part, has been submitted for publication as it may appear in Ecology. LeVan, KE and DA Holway. “Ant-aphid mutualism increases floral visitation by ants and reduces plant fitness via decreased pollinator visitation.” The dissertation author was the primary investigator and author of this paper. Chapter 4, in part is currently being prepared for submission for publication. LeVan, KE and DA Holway. “The mutualism between the Argentine ant and cotton aphid structures food webs in cotton.” The dissertation author was the primary investigator and author of this material. x VITA 2008 Bachelor of Science, Tufts University 2013 Doctor of Philosophy, University of California, San Diego AWARDS