1 Patterns in flower visitation of flying insects in urban Christchurch A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Ecology By Lauretta Lynley Bensemann School of Biological Sciences University of Canterbury 2013 2 Bombus species visiting yellow Helenium flexuosum flowers in the Botanical Gardens, Christchurch. 3 Table of Contents Abstract .................................................................................................................................................. 6 Chapter 1 – General introduction .......................................................................................................... 8 1.1 The mechanisms of pollination and the importance of mutualisms ............................................ 8 1.2 New Zealand’s insect pollinators ................................................................................................ 10 1.3 Plant syndromes and their relevance to the New Zealand flora ................................................ 11 1.4 Flower constancy ........................................................................................................................ 12 1.5 The risk of pollination failure and the loss of pollinators ........................................................... 12 1.6 Reductions in Apis mellifera numbers in New Zealand............................................................... 13 1.7 The relationship between plant traits and pollinator preferences ............................................. 14 1.8 Thesis objectives ......................................................................................................................... 14 Chapter 2 – The preferences of New Zealand’s flower visiting insects .............................................. 16 2.1 Introduction ................................................................................................................................ 16 The interactions between plants and their pollinators ................................................................ 16 Pollination in New Zealand ........................................................................................................... 17 Resistance to invasions and the facilitation of weeds .................................................................. 21 Chapter objectives ........................................................................................................................ 21 2.2 Methods ...................................................................................................................................... 22 Study sites and species ................................................................................................................. 22 Insect observations ....................................................................................................................... 23 Environmental data ...................................................................................................................... 23 Statistical analysis ......................................................................................................................... 24 2.3 Results ......................................................................................................................................... 26 Chi-squares tests ........................................................................................................................... 29 GLM plant species level analysis ................................................................................................... 30 GLMM plant-level analysis ............................................................................................................ 31 2.4 Discussion .................................................................................................................................... 34 The predictors of flying-insect visitation in New Zealand ............................................................ 34 Limitations of this study ................................................................................................................ 36 The resistance of the New Zealand flora to the establishment of exotic species ........................ 36 Chapter 3 – The effect of flower colour on the visitation of New Zealand’s pollinating insects ...... 38 3.1 Introduction ................................................................................................................................ 38 Factors driving pollinator visitation .............................................................................................. 38 4 The attributes of New Zealand’s flora and fauna ......................................................................... 40 Chapter objectives ........................................................................................................................ 42 3.2 Methods ...................................................................................................................................... 43 Study site and species ................................................................................................................... 43 One-hour insect counts ................................................................................................................ 44 General methodology ................................................................................................................... 44 Preliminary trials before data were collected .............................................................................. 45 Statistical analysis ......................................................................................................................... 48 3.3 Results ......................................................................................................................................... 49 3.4 Discussion .................................................................................................................................... 52 The colour preferences of New Zealand’s flower visiting insects ................................................ 52 Other possible drivers of pollinator preferences .......................................................................... 53 Chapter 4 – A case study: Does Gastrodia ‘long column’ rely upon mutualisms for successful fruit set? ........................................................................................................................................................ 56 4.1 Introduction ................................................................................................................................ 56 An overview of the Orchidaceae .................................................................................................. 56 Insect pollinators in New Zealand ................................................................................................. 59 New Zealand orchids..................................................................................................................... 59 The Gastrodia orchids ................................................................................................................... 61 Chapter objectives ........................................................................................................................ 62 4.2 Methods ...................................................................................................................................... 62 Study site and species ................................................................................................................... 62 Insect observations and bagging .................................................................................................. 63 Statistical analysis ......................................................................................................................... 64 4.3 Results ......................................................................................................................................... 64 4.4 Discussion .................................................................................................................................... 67 The importance of mutualistic services to Gastrodia ‘long column’ ............................................ 67 The insect visitors of Gastrodia ‘long column’.............................................................................. 67 Aphids as pollinators ..................................................................................................................... 68 Implications ................................................................................................................................... 69 Chapter 5 – Synthesis ........................................................................................................................... 70 5.1 Patterns in visitation of flower visiting insects in urban Christchurch........................................ 70 5.2 The importance of pollinators..................................................................................................... 72 5.3 Are pollinators able to replace Apis mellifera? ........................................................................... 73 5 5.4 The role of exotic mutualists in New Zealand ecosystems ......................................................... 74 5.5 The relationship between New Zealand plants and their