Modelling the impact of an alien invasion: Harmonia axyridis in Britain Richard Francis Comont Linacre College Trinity term 2013 A thesis submitted for the degree of Doctor of Philosophy Word count: 31,043 i Contents Summary ........................................................................................................................................... vi Declaration ....................................................................................................................................... vii Dedication and Acknowledgements .............................................................................................viii Chapter 1. General introduction ......................................................................................... 1 1. 1.1. Defining alien species and invasive alien species ....................................................... 1 1. 1.2. Impacts and costs of Invasive Alien Species ............................................................... 1 1. 1.3. Trends in arrival, establishment and spread of IAS ..................................................... 2 1. 1.4. Pathways of introduction and spread – how do IAS arrive? ...................................... 3 1. 1.5. From alien to invasive ...................................................................................................... 4 1. 1.6. From alien to invasive – the traits of invasive species ................................................ 5 1. 1.7. Invasibility of native communities – the diversity-invasibility hypothesis .................. 6 1. 1.8. Anthropogenic habitat change ........................................................................................ 7 1. 1.9. Habitat loss and fragmentation ....................................................................................... 8 1. 1.10. Climate change: a particular form of anthropogenic habitat change ...................... 9 1. 1.11. Horizon scanning, risk assessment and management ........................................... 11 1. 1.12. The Enemy Release Hypothesis (ERH) .................................................................... 13 1.1.13. Range of impacts – from co-existence to invasional meltdown .............................. 15 1.2.1. The most invasive ladybird on Earth – Harmonia axyridis ............................................ 17 1.2.2. Trends in arrival, establishment and spread of H. axyridis across Europe ............. 18 1.2.3. Pathways of introduction and spread of H. axyridis ................................................... 19 1.2.4. Habitat range of H. axyridis ............................................................................................ 23 1.2.5. Invasive traits of H. axyridis ............................................................................................ 24 1.2.6. Impacts of Harmonia axyridis ......................................................................................... 25 1.2.7. Predators, parasites and pathogens - what will stop the invader? ........................... 26 1.2.8. Summary ........................................................................................................................... 27 1.3.1. Aims of the thesis ................................................................................................................. 28 1.4.1. References: ........................................................................................................................... 28 Chapter 2. Using biological traits to explain ladybird distribution patterns.................. 47 2.1. Abstract ..................................................................................................................................... 47 2.1.1. Aim ..................................................................................................................................... 47 2.1.2. Location ............................................................................................................................. 47 2.1.3. Methods ............................................................................................................................. 47 ii 2.1.4. Results ............................................................................................................................... 47 2.1.5. Main conclusions.............................................................................................................. 47 2.2. Keywords .................................................................................................................................. 48 2.3. Introduction ............................................................................................................................... 48 2.4. Materials and Methods ........................................................................................................... 50 2.4.1. Distribution data ............................................................................................................... 50 2.4.2. Explanatory traits ............................................................................................................. 52 2.4.3. Data analysis .................................................................................................................... 53 2.5. Results ...................................................................................................................................... 55 2.6. Discussion ................................................................................................................................ 59 2.7. Conclusions .............................................................................................................................. 63 2.8. References ............................................................................................................................... 63 Chapter 3. Ecological correlates of local extinction and colonisation in the British ladybird beetles (Coleoptera: Coccinellidae)................................................................... 70 3.1. Abstract ..................................................................................................................................... 70 3.2. Keywords: ................................................................................................................................. 71 3.3. Introduction ............................................................................................................................... 71 3.4. Methods .................................................................................................................................... 73 3.4.1. Distribution data ............................................................................................................... 73 3.4.2. Environmental and trait data .......................................................................................... 74 3.4.3. Modelling approach ......................................................................................................... 75 3.5. Results ...................................................................................................................................... 77 3.6. Discussion ................................................................................................................................ 82 3.7. References ............................................................................................................................... 86 3.9.1. Appendix S1. Bray-Curtis similarity index measures of dietary overlap between each native ladybird species and H. axyridis.......................................................................... 93 3.9.2. Appendix S2. Bray-Curtis similarity index measures of dietary overlap between each native ladybird species and H. axyridis .......................................................................... 94 Chapter 4. Escape from parasitism by the invasive alien ladybird, Harmonia axyridis. ............................................................................................................................................ 95 4.1. Abstract ....................................................................................................................................... 95 4.2. Keywords: ................................................................................................................................. 95 4.3. Introduction: ............................................................................................................................. 96 4.4. Methods: ................................................................................................................................... 99 4.4.1. Field Survey - pupal parasitism: .................................................................................... 99 iii 4.4.2. Semi-field survey - adult parasitism: ........................................................................... 100 4.4.3. Analysis: .......................................................................................................................... 101 4.5. Results: ................................................................................................................................... 102 4.5.1. Field survey: pupal parasitism: .................................................................................... 102 4.5.2. Semi-field survey: adult parasitism ............................................................................