Temporal Currency: Life-history strategies of a native marine invertebrate increasingly exposed to urbanisation and invasion A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Zoology University of Canterbury New Zealand Jason Suwandy 2012 Contents List of Figures ......................................................................................................................................... iii List of Tables .......................................................................................................................................... vi Acknowledgements ............................................................................................................................... vii Abstract ................................................................................................................................................ viii CHAPTER ONE - General Introduction .................................................................................................... 1 1.1 Marine urbanisation and invasion ................................................................................................ 2 1.2 Successful invasion and establishment of populations ................................................................ 4 1.3 Ascidians ....................................................................................................................................... 7 1.4 Native ascidians as study organisms ............................................................................................. 8 1.5 Pyura pachydermatina – a New Zealand native ascidian facing invasion pressure ..................... 9 1.6 Banks Peninsula – local ecosystem and conditions .................................................................... 12 1.7 Study outline and aims................................................................................................................ 15 CHAPTER TWO - Demography of Pyura pachydermatina ..................................................................... 17 2.1 Introduction ................................................................................................................................ 17 2.1.1 Background .......................................................................................................................... 17 2.1.2 Abundance and Distribution of Pyura pachydermatina ...................................................... 18 2.1.3 Chapter Objectives ............................................................................................................... 21 2.2 Methods ...................................................................................................................................... 22 2.2.1 Preliminary study ................................................................................................................. 22 2.2.2 Abundance monitoring ........................................................................................................ 24 2.3 Results ......................................................................................................................................... 27 2.3.1 Preliminary Study ................................................................................................................. 27 2.3.2 Abundance ........................................................................................................................... 28 2.3.3 Size-frequency ...................................................................................................................... 30 2.4 Discussion .................................................................................................................................... 33 CHAPTER THREE - Reproductive Biology of Pyura pachydermatina ..................................................... 37 3.1 Introduction ................................................................................................................................ 37 3.1.1 Background .......................................................................................................................... 37 3.1.2 Pyura reproduction .............................................................................................................. 39 3.1.3 Chapter objectives ............................................................................................................... 40 3.2 Methods ...................................................................................................................................... 41 3.3 Results ......................................................................................................................................... 44 3.4 Discussion .................................................................................................................................... 48 i CHAPTER FOUR - Reproduction Pattern of Pyura pachydermatina ..................................................... 52 4.1 Introduction ................................................................................................................................ 52 4.1.1 Temporal variation in reproduction ..................................................................................... 52 4.1.2 Year-round reproduction: advantages ................................................................................. 55 4.1.3 Chapter objectives ............................................................................................................... 56 4.2 Methods ...................................................................................................................................... 56 4.2.1 Spawning experiment .......................................................................................................... 56 4.2.2 Recruitment in natural environments ................................................................................. 57 4.2.3 Gonad indices ....................................................................................................................... 59 4.3 Results ......................................................................................................................................... 63 4.3.1 Spawning experiment .......................................................................................................... 63 4.3.2 Recruitment ......................................................................................................................... 64 4.3.3 Gonad indices ....................................................................................................................... 64 4.4 Discussion .................................................................................................................................... 71 CHAPTER FIVE - Invasive Pressure ........................................................................................................ 75 5.1 Introduction ................................................................................................................................ 75 5.1.1 Factors affecting invasiveness and invasibility .................................................................... 75 5.1.2 Predation .............................................................................................................................. 77 5.1.3 Potential predators of Pyura pachydermatina early life stages .......................................... 79 5.1.4 Styela clava as a model for potential invasive species in Banks Peninsula ......................... 81 5.1.5 Chapter objectives ............................................................................................................... 81 5.2 Methods ...................................................................................................................................... 82 5.2.1 Preliminary study ................................................................................................................. 82 5.2.2 Predation experiment .......................................................................................................... 83 5.3 Results ......................................................................................................................................... 85 5.3.1 Preliminary study ................................................................................................................. 85 5.3.2 Predation experiment .......................................................................................................... 86 5.4 Discussion .................................................................................................................................... 92 CHAPTER SIX - General Discussion ........................................................................................................ 96 6.1 Overview ..................................................................................................................................... 96 6.2 Demography of Pyura pachydermatina in Banks Peninsula ....................................................... 98 6.3 Reproduction of Pyura pachydermatina ..................................................................................... 99 6.4 Invasive pressure on Pyura pachydermatina ............................................................................ 101 6.5 Conclusion ................................................................................................................................