ALLEE EFFECTS, HOST TREE DENSITY AND THE ESTABLISHMENT OF INVASIVE BARK BEETLES A thesis submitted in partial fulfilment of the requirements for the doctoral degree of ecology Kevin Daniel Chase University of Canterbury 2016 “The design of a book is the pattern of a reality controlled and shaped by the mind of the writer. This is completely understood about poetry or fiction, but it is too seldom realized about books of fact. And yet the impulse which drives a man to poetry will send another man in to the tide pools and force him to try to report what he finds there. Why is an expedition to Tibet undertaken, or a sea bottom dredged? Why do men, sitting at a microscope, examine the calcareous plates of sea-cucumber, and, finding a new arrangement and number, feel an exaltation and give the new species a name, and write about it possessively.” -John Steinbeck, 1951, The Log From the Sea of Cortez 2 Table of Contents Acknowledgments .......................................................................................................................................... 5 Abstract ........................................................................................................................................................... 7 Chapter 1 - General Introduction ................................................................................................................... 8 Allee effects ............................................................................................................................................. 8 Biosecurity and invasive alien species .................................................................................................... 9 Bark beetles ............................................................................................................................................ 11 Study species in New Zealand and the United States ........................................................................... 12 Research objectives and hypothesis ...................................................................................................... 13 Chapter 2 - Long distance dispersal of non-native pine bark beetles from host resources ........................ 15 Introduction ............................................................................................................................................ 15 Methods and materials ........................................................................................................................... 16 Study system ................................................................................................................................... 16 Trapping network ............................................................................................................................ 17 Distance measurements .................................................................................................................. 17 Inverse distance weighted estimates............................................................................................... 18 Statistical analysis ........................................................................................................................... 22 Results .................................................................................................................................................... 23 Pine distance and density effect on Hylurgus ligniperda .............................................................. 23 Pine distance and density effects on Hylastes ater ........................................................................ 25 Discussion .............................................................................................................................................. 26 Chapter 3 – Allee dynamics at the limit of Ips pini range in a fragmented landscape ............................... 30 Introduction ............................................................................................................................................ 30 Methods and materials ........................................................................................................................... 31 Study system: Ips pini ..................................................................................................................... 31 Study area and experimental design ............................................................................................... 32 Measurements of pine density ........................................................................................................ 32 Allee threshold estimation .............................................................................................................. 34 Statistical analysis ........................................................................................................................... 37 Results .................................................................................................................................................... 38 Ips pini trapping results................................................................................................................... 38 Effects of spatially averaged pine density on Ips pini trap capture ............................................... 38 Allee effect application ................................................................................................................... 40 Discussion .............................................................................................................................................. 41 Ips pini distribution in regards to the Holt niche framework ......................................................... 41 1. Large dispersal Pulses................................................................................................................. 41 2. Pooling of dispersers from multiple sources .............................................................................. 44 3. A change in the environment ...................................................................................................... 44 Application to invasive species ...................................................................................................... 45 Chapter 4 – Component and demographic Allee effects in experimental bark beetle invasions ............... 47 Introduction ............................................................................................................................................ 47 Methods and materials ........................................................................................................................... 48 Hylurgus ligniperda releases .......................................................................................................... 48 Ips pini releases ............................................................................................................................... 50 Statistical analysis ........................................................................................................................... 53 Results .................................................................................................................................................... 53 Hylurgus ligniperda releases .......................................................................................................... 53 Ips pini releases ............................................................................................................................... 57 Discussion .............................................................................................................................................. 57 3 Chapter 5 – Synthesis and application ......................................................................................................... 62 References..................................................................................................................................................... 65 Appendices ................................................................................................................................................... 85 Appendix A - R software code used to create weighted estimates of pine density with a distance decay function in Chapter 2. For this example, random data was generated representing pine density. ...... 85 Appendix B - Short communication submitted to the New Zealand Entomologist about Hylastes ater ability to utilize roots and root collars of windbreak trees in New Zealand. ....................................... 87 4 Acknowledgments Even with the passion, drive and focus to pursue a PhD, I am only here because of the support I have received from so many. Lindsey Chase, my beloved wife, thank you. You have travelled the world with me and supported me in every way imaginable. I only hope the love and support I provide you until the end of our days is worthy of my gratefulness. Mom and Dad Chase, the love and unrestricting curiosity you bestowed upon me is the reason I am here today. I explore the natural world because you never placed a single pressure on me to be “successful” in the eyes of the world, and I am extremely grateful for that. Mom and Dad Summers, I know taking your daughter half way across the world was not comfortable or convenient, yet, you lovingly supported us in every possible for the past three years. For this I am extremely thankful. The support, training and encouragement I