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THE IMPACTS OF EVOLUTIONARY AND HUMAN MEDIATED DISPERSAL MECHANISMS ON INVASION SUCCESS IN SOLANACEAE A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI‘I AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN TROPICAL PLANT AND SOIL SCIENCES DECEMBER 2014 By Martha J. Gauthier Dissertation Committee: Ania Wieczorek, Chairperson Curtis Daehler Clifford Morden Robert Paull Mark Wright Keywords: Solanum elaeagnifolium, Solanum torvum, genetic diversity, agriculture ACKNOWLEDGEMENTS I am very grateful to my colleagues from around the globe who generously provided their time and effort to collect and send me samples for this project. Much of this dissertation would not have been possible without them. I would like to thank A. Plos, F. Chiarini, J. Scales, R. Stanton, R. Breckenridge, J.Y. Meyer, J. Cohen, G. Proctor, D. Stesevic, J. Le Roux, C. Ezzeddine, G. Hinton, and L. Bohs. I was very fortunate to have incredible field assistants when making my own collections and would like to thank C. Oshiro, A. Vorsino, D. Morgan, and J. Gauthier. I would like to extend my most sincere gratitude to C. Oshiro for gladly sharing her wealth of lab expertise, for always being available to troubleshoot less than stellar PCR results and for the countless other kind acts she did everyday; and to A. Vorsino, for the many helpful discussions, great advice, comments and suggestions on manuscripts and never-ending encouragement. I also thank H. Turano and K. Perez for constructive feedback that greatly improved this manuscript. Finally, I would like to thank my advisor, A. Wieczorek and committee members, C. Morden, C. Daehler, R. Paull and M. Wright for their mentorship and support throughout this process. Funding for this research was provided through a TSTAR grant. ii ABSTRACT Understanding the mechanisms behind the dispersal and evolution of agricultural weeds is critical for the development of appropriate weed management strategies and protection of the world’s food supply. However, little is known about the evolution of weed species in agricultural environments or the impacts of human-mediated dispersal on the evolutionary potential of these species. To gain a deeper understanding of the evolution and evolutionary potential of weeds in agricultural environments, I use a population genetics approach to investigate the genetic diversity of two non-native, invasive Solanum species that are problematic in agricultural systems (Solanum elaeagnifolium and S. torvum). I focus on three key questions: 1) do population structure and differentiation exist, 2) what is the level of genetic diversity present, and; 3) has the evolutionary potential of these species been diminished in non-native regions post introduction? Overall, results indicate the level of genetic diversity was comparable throughout each species’ range; genetic population differentiation and structure existed; and adverse effects due to founding events were not evident. To address the need for appropriate weed management and protection of the world’s food supply I explore two practical strategies. First, I examine non-native Solanum species found in agricultural settings. Specifically, I assess whether Silverleaf nightshade (Solanum elaeagnifolium), a non-native agricultural weed, is more likely associated with a specific crop type than other non-native Solanum species in California. To answer this question, I utilize cropland data layers (CDLs) and a geographical information system-based (GIS) spatial correlation approach to determine weed-crop correlations. I describe these associations as likely indicators of primary dispersal mechanisms of unwanted species. Second, I utilize the premise of DNA barcoding to develop a molecular means of distinguishing between four Solanum species on the Hawaii Noxious Weed List and their close relatives. I suggest two molecular techniques that provide easily recognizable patterns that represent a unique DNA profile for each of the four focal species examined. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ..................................................................................................... ii ABSTRACT ............................................................................................................................ iii LIST OF TABLES .................................................................................................................. vii LIST OF FIGURES ............................................................................................................... viii CHAPTER 1. INTRODUCTION ............................................................................................. 9 CHAPTER 2. THE INFLUENCE OF AGRICULTURAL PRACTICES ON THE DISPERSAL, COMMUNITY STRUCTURE AND EVOLUTIONARY POTENTIAL OF AGRICULTURALLY ASSOCIATED WEED SPECIES ..................................................... 16 Introduction ................................................................................................................. 16 Introduction of non-native species in Hawai‘i ............................................................. 17 The dynamics of weeds in agriculture ......................................................................... 18 The cost of weeds in agriculture .................................................................................. 19 Evolutionary mechanisms ............................................................................................ 20 Agricultural practices impact weed community structure and abundance .................. 21 Herbicides ........................................................................................................ 21 Tillage .............................................................................................................. 21 Fertilizers ......................................................................................................... 22 Crop rotation ................................................................................................... 22 Agricultural dispersal mechanisms .................................................................. 23 Conclusion ................................................................................................................... 24 CHAPTER 3. IS EVOLUTIONARY POTENTIAL OVERRATED? ASSESSING AGRICULTURALLY MEDIATED DISPERSAL IN SOLANUM ELAEAGNIFOLIUM CAV. (SILVERLEAF NIGHTSHADE) ............................................................................................ 25 iv Introduction ................................................................................................................. 25 Study Species ............................................................................................................... 27 Materials and Methods ................................................................................................. 28 Sample collection and DNA isolation .............................................................. 28 Microsatellite marker analysis ........................................................................ 29 Data Analyses – Population Genetic Structure ............................................... 29 Data Analyses – Genetic Diversity .................................................................. 31 Results .......................................................................................................................... 31 Population differentiation and structure ......................................................... 31 Genetic diversity .............................................................................................. 32 Discussion .................................................................................................................... 33 Do population differentiation and structure exist? .......................................... 33 What is the level of genetic diversity present? ................................................. 34 Has the evolutionary potential of S. elaeagnifolium changed post-introduction? ........................................................................................................................... 35 Conclusion ................................................................................................................... 36 CHAPTER 4. DELICIOUS AND DETESTED: ASSESSING THE GENETIC DIVERSITY OF A CULTIVATED WEED SPECIES (SOLANUM TORVUM SW.) .................................... 43 Introduction ................................................................................................................. 43 Materials and methods ................................................................................................ 44 Sample collection and DNA isolation .............................................................. 44 Microsatellite marker analysis ........................................................................ 45 Data analysis ................................................................................................... 45 Results ......................................................................................................................... 46 v Discussion .................................................................................................................... 46 Conclusion ................................................................................................................... 49 CHAPTER 5. AN AGRICULTURAL AFFAIR WITH SOLANUM ELAEAGNIFOLIUM