Parasite-induced warning colouration Thesis submitted in accordance with the requirements of the University of Liverpool for the degree of Doctor in Philosophy by Rebecca Susan Jones September 2016 1 Preface I hereby declare that this thesis consists of my own work, unless otherwise stated, and has not previously been submitted to the University of Liverpool or any other university in application of a higher degree. The text does not exceed 100,000 words and meets the formatting requirements of the University of Liverpool. 2 Contents Abstract .................................................................................................................................................. 5 Acknowledgements .............................................................................................................................. 6 Chapter 1. General Introduction ......................................................................................................... 9 1.1 Introduction ................................................................................................................................. 9 1.2 Aposematism: An introduction ................................................................................................. 9 1.3 Parasite manipulation ............................................................................................................. 18 1.4 Parasite manipulation through aposematism ...................................................................... 30 1.5 Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus luminescens .......................................................................................................................................................... 32 1.6 Aims and Structure .................................................................................................................. 51 1.7 References ............................................................................................................................... 54 Chapter 2. Conspicuousness against a background protects a nematode-infected host ....... 79 2.1 Author contributions ................................................................................................................ 79 2.2 Abstract ..................................................................................................................................... 80 2.3 Introduction ............................................................................................................................... 81 2.4 Methods .................................................................................................................................... 84 2.5 Results ...................................................................................................................................... 87 2.6 Discussion................................................................................................................................. 92 2.7 Acknowledgements ................................................................................................................. 99 2.8 References ............................................................................................................................... 99 Chapter 3. “Parasite-induced aposematism” protects entomopathogenic nematode parasites against invertebrate enemies ......................................................................................................... 106 3.1 Author contributions .............................................................................................................. 106 3.2 Abstract ................................................................................................................................... 107 3.3 Introduction ............................................................................................................................. 108 3.4 Methods .................................................................................................................................. 112 3.5 Experiment 1: Effect of nematode-bacterium infection on predation by ground beetles ........................................................................................................................................................ 113 3.6 Experiment 2: Is there olfactory protection of infected waxworms? .............................. 121 3.7 Discussion............................................................................................................................... 123 3.8 Acknowledgements ............................................................................................................... 128 3.9 References ............................................................................................................................. 128 3.10 Supplementary material ..................................................................................................... 132 3 Chapter 4. Investment in multiple defences protects a nematode-bacterium symbiosis from predation ............................................................................................................................................ 133 4. 1 Author contributions ............................................................................................................. 134 4.2 Abstract ................................................................................................................................... 135 4.3 Introduction ............................................................................................................................. 136 4.4 Methods .................................................................................................................................. 140 4.5 Results .................................................................................................................................... 146 4.6 Discussion............................................................................................................................... 152 4.7 Acknowledgements ............................................................................................................... 157 4.8 References ............................................................................................................................. 157 Chapter 5. Parasite-induced bioluminescence deters predation of infected hosts by nocturnal rodent predators ............................................................................................................................... 163 5.1 Author contributions .............................................................................................................. 164 5. 2 Abstract .................................................................................................................................. 164 5.3 Introduction ............................................................................................................................. 165 5.4 Methods .................................................................................................................................. 169 5.5 Results .................................................................................................................................... 175 5.6 Discussion............................................................................................................................... 182 5.7 Acknowledgments ................................................................................................................. 185 5.8 References ............................................................................................................................. 186 Chapter 6. Conclusions and future work ...................................................................................... 192 6.1 Conclusions ............................................................................................................................ 192 6.2 Future work ............................................................................................................................. 199 6.3 References ............................................................................................................................. 201 4 Abstract Parasite-induced warning colouration Rebecca Susan Jones Parasites are ubiquitous in nature and are capable of exerting strong selection pressures on their hosts to enhance (or potentially reduce) transmission. Parasite manipulation of hosts can therefore drive evolution of various traits and phenotypes in the host to the benefit of the parasite. These adaptations can serve a number of purposes, working to enhance survival and reproduction of the parasite within its host. This thesis aims to elucidate the roles of various defences induced by the nematode Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus luminescens in its obligate insect host, in which predation of the host is fatal for the parasitic colony. To do this I utilised both laboratory and field experiments to test a number of the defences with a variety of predators. To begin with I extended a previous study examining predation rates on uninfected and infected individuals by examining the effect of background on predation rates in the field. I found that prey that were conspicuous against their background received fewer attacks and were consumed less than those that were cryptic