An Investigation of the Factors Leading to Invasion Success of Non-Native
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University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School January 2013 An investigation of the factors leading to invasion success of non-native plants using a system of native, introduced non-invasive, and invasive Eugenia congeners in Florida Kerry Bohl University of South Florida, [email protected] Follow this and additional works at: http://scholarcommons.usf.edu/etd Part of the Biology Commons, Ecology and Evolutionary Biology Commons, and the Plant Biology Commons Scholar Commons Citation Bohl, Kerry, "An investigation of the factors leading to invasion success of non-native plants using a system of native, introduced non- invasive, and invasive Eugenia congeners in Florida" (2013). Graduate Theses and Dissertations. http://scholarcommons.usf.edu/etd/4442 This Dissertation is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. An Investigation of the Factors Leading to Invasion Success of Non-Native Plants Using a System of Native, Introduced Non-Invasive, and Invasive Eugenia Congeners in Florida by Kerry R. Bohl A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Integrative Biology College of Arts and Sciences University of South Florida Major Professor: Peter Stiling, Ph.D. Susan Bell, Ph.D. Gordon Fox, Ph.D. Lynn Martin, Ph.D. Date of Approval: April 9, 2013 Key words: enemy release hypothesis, seedling performance, herbivore exclusion, Eugenia uniflora, Surinam cherry, Myllocerus undatus Copyright © 2013, Kerry R. Bohl DEDICATION This dissertation is dedicated to my parents, Robin and Sara Bohl, who are responsible for instilling within me the love of nature and have always encouraged me to reach for the stars. ACKNOWLEDGMENTS There are a great many people whose contributions have made the completion of this work possible. I am first and foremost indebted to my major professor, Dr. Peter Stiling, for his unwavering confidence, enthusiasm, and camaraderie over the years. Special thanks also go to Dr. Hong Liu for serving as the external chair for my doctoral defense, introducing me to the Eugenia system and field sites in south Florida, and for providing help along the way. I am grateful to have been a part of the Integrative Biology Department, as so many of my colleagues have been invaluable in making my time at USF productive and memorable. I would like to extend special thanks to my committee members, Dr. Susan Bell, Dr. Gordon Fox, and Dr. Lynn Martin, for consistently being available for guidance and insight, as well as Dr. Jason Rohr for generously sharing his time and statistical expertise. I am grateful for the financial support provided by several funding sources, including the FLEPPC Julia Morton Invasive Plant Research Grant Program, the Fern Garden Club of Odessa, the Fred L. and Helen M. Tharp Endowed Scholarship Fund, and USF Student Government. I would also like to thank Patrick Griffith, Chad Husby, and Montgomery Botanical Center, Russ Mapp, Mark Foley, and Hugh Taylor Birch State Park, Martha Kent and Fairchild Tropical Botanic Garden, April Rosenik and Fruit and Spice Park, and Plantation Heritage Park for facilitating my research by generously providing access to plants, sites, and accommodations. Additional thanks to Jeff Michel and Bayer CropScience for donating the insecticide used in the herbivore exclusion experiments. The completion of this work would not have been possible without the assistance, friendship, and support from members of the Stiling lab and my field assistants. In particular, I would like to acknowledge my labmates Heather Jezorek, Keith Stokes, Jennifer Maul, Danielle Neveu, Tatiana Cornelissen, and Laura Altfeld, as well as Laura Bedinger and Diane Harshbarger for help in the field. Finally, I am eternally grateful to my husband, family, and friends for providing perspective, encouragement, and laughs, which were very much needed. Special thanks go to Briana Giganti for being an amazing friend over the past six years. Most importantly, I thank my husband Jacob Stricker for enthusiastically joining me on this journey, providing encouragement and steadfast support on a daily basis, and for making each and every day better than the last. All of you were integral in the culmination of this work, and I thank you. TABLE OF CONTENTS LIST OF TABLES iii LIST OF FIGURES iv ABSTRACT vi CHAPTER 1 – Introduction 1 Literature cited 11 CHAPTER 2 – Herbivory by an introduced Asian weevil negatively affects population growth of an invasive Brazilian shrub in Florida 14 Synopsis 14 Introduction 15 Materials and Methods 18 Results 24 Discussion 27 Acknowledgments 31 Literature cited 31 CHAPTER 3 – Seedlings of the introduced invasive shrub Eugenia uniflora (Myrtaceae) outperform those of its native and introduced non-invasive congeners in Florida 41 Synopsis 41 Introduction 42 Materials and Methods 46 Study System 46 Common Garden Experiment 48 Field Experiment 50 Statistical Analysis – Common Garden Experiment 51 Statistical Analysis – Field Experiment 53 Results 55 Common Garden Experiment 55 Field Experiment 56 Discussion 58 Acknowledgments 63 Literature cited 64 i CHAPTER 4 – Release from herbivory does not confer invasion success for Eugenia uniflora in Florida 76 Synopsis 76 Introduction 77 Materials and Methods 80 Study System 80 Field Experiment 81 Statistical Analysis 84 Results 86 Discussion 88 Literature cited 93 APPENDICES 101 Appendix A: Permission statement for use of Bohl Stricker and Stiling (2012) 102 Appendix B: License agreement for use of Bohl Stricker and Stiling (2013) 103 ii LIST OF TABLES Table 2.1: Stochastic growth rates (λ) of Eugenia populations calculated using Tuljapukar’s approximation and computer simulation with associated 95% confidence intervals 40 iii LIST OF FIGURES Figure 2.1: Proportion of leaves damaged for each host plant species in control and insecticide treated plots during February 2008 (t1) and March 2010 (t2) 35 Figure 2.2: Amount of foliar damage by M. undatus versus all other types of insect herbivores sustained by the three Eugenia species 36 Figure 2.3: Average relative change in height (RGRH) (A) and average relative change in leaf number (RGRL) (B) for all three Eugenia species per day in control versus insecticide treated plots from February 2008 to March 2010 37 Figure 2.4: Kaplan-Meier survival curves for three Eugenia species 38 Figure 2.5: Histograms of 1000 projected population densities (individuals/m2) 100 years in the future under natural conditions and when herbivores have been excluded for E. axillaris (A), E. foetida (B), and E. uniflora (C) 39 Figure 3.1: Proportion of Eugenia seedlings that emerged in the common garden experiment at the University of South Florida Botanical Gardens for each Eugenia species in each collection year 68 Figure 3.2: Eugenia seedling stem heights at the University of South Florida Botanical Gardens in each year 69 Figure 3.3: Average number of leaves for each Eugenia species at the University of South Florida Botanical Gardens for each Eugenia species in each year 70 Figure 3.4: Proportion of seedlings of each Eugenia species that emerged beneath each overstory tree at Plantation Heritage Park 71 Figure 3.5: Change in stem height increment from October 2009 to May 2011 for Eugenia seedlings at Plantation Heritage Park 72 Figure 3.6: Proportional change in leaf number from October 2009 to May2011 for Eugenia seedlings at Plantation Heritage Park 73 Figure 3.7: Proportion of leaves of surviving Eugenia seedlings damaged by Myllocerus undatus versus the proportion of leaves damaged by all other insect herbivores in May 2011 74 iv Figure 3.8: Kaplan-Meier survival curves for Eugenia seedlings after emergence at Plantation Heritage Park 75 Figure 4.1: Proportion of damaged leaves for each seedling species in January 2011 at Hugh Taylor Birch State Park 97 Figure 4.2: Change in height increment from January to September 2011 for surviving Eugenia seedlings in control and insecticide-treated plots at Hugh Taylor Birch State Park 98 Figure 4.3: Proportional change in leaf number between January to September 2011 for surviving Eugenia seedlings in control and insecticide- treated plots at Hugh Taylor Birch State Park 99 Figure 4.4: Average number of months survived for Eugenia species treated with insecticide or water (control) at Hugh Taylor Birch State Park 100 Figure A.1: Permission statement for use of previously published work: Bohl Stricker KR, Stiling P (2012) Herbivory by an introduced Asian weevil negatively affects population growth of an invasive Brazilian shrub in Florida. Ecology 93:1902–1911 102 v ABSTRACT The overwhelming majority of plant species introduced into a new range never become invasive. Consequently, identification of factors allowing the small fraction of successful invaders to naturalize, increase in abundance, and displace resident species continues to be a key area of research in invasion biology. Of the considerable number of hypotheses that have been proposed to resolve why some plant species become noxious pests, the enemy release hypothesis (ERH) is one of the most commonly cited. The ERH maintains that invasive plants succeed in a new range because they are no longer regulated by their coevolved natural enemies, and this reduction in enemy pressure imparts a competitive advantage over native species, which continue to be negatively impacted by top-down processes. Alternatively, the ability of invasive plant species to outperform their counterparts, rather than escape from enemies, may be key in conferring invasion success. The importance of preadapted traits and release from natural enemies in successful invasion remains unclear, likely owing to a lack of empirical studies comparing their effects on relative performance and population growth of closely related species that differ in origin and invasiveness.