Lincoln University Digital Thesis Copyright Statement The digital copy of this thesis is protected by the Copyright Act 1994 (New Zealand). This thesis may be consulted by you, provided you comply with the provisions of the Act and the following conditions of use: you will use the copy only for the purposes of research or private study you will recognise the author's right to be identified as the author of the thesis and due acknowledgement will be made to the author where appropriate you will obtain the author's permission before publishing any material from the thesis. Host-parasitoid avoidance behaviour in the context of contemporary evolution in insect classical biological control A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University by Morgan William Shields Lincoln University 2019 Abstract of a thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy in Ecology. Abstract Host-parasitoid avoidance behaviour in the context of contemporary evolution in insect classical biological control by Morgan William Shields Pests are increasingly invading novel environments due to global trade and travel and their management requires a greater emphasis on classical biological control than has previously been the case. This approach has been particularly successful in New Zealand pasture such as with the Argentine stem weevil, Listronotus bonariensis (Coleoptera: Curculionidae) (ASW). This pest was successfully managed by releasing the parthenogenetic parasitoid, Microctonus hyperodae (Hymenoptera: Braconidae), in the early 1990s with ASW parasitism rates quickly reaching over 75 %. However, these rates have substantially declined in the last decade. This decline was hypothesised to be due to contemporary evolution of enhanced avoidance behaviour by the sexual ASW and that these behaviours are influenced by the host plant. The work in this thesis used microcosms in laboratory experiments to investigate whether there was any behavioural evidence supporting the above hypotheses, which if confirmed, may explain recent low parasitism rates. Experiments were conducted to examine the ASW behavioural responses to M. hyperodae and investigate whether these ASW responses differed between the ryegrass host plants; diploid hybrid (diploid Lolium perenne x diploid Lolium multiflorum), diploid L. perenne and tetraploid L. multiflorum. Furthermore, ASW behavioural responses to the presence of M. hyperodae were compared between ASW populations collected from areas with different parasitism rates, history and latitude. The sensitivity of ASW responses to different parasitoid species was also investigated. The work in this thesis showed that the weevil’s avoidance behaviour differed depending on the host plant, with ASWs on the diploid hybrid having the most consistent reduced feeding and plant abandonment responses to M. hyperodae. ASW on diploid L. perenne had similar responses to weevils on the diploid hybrid but these responses were delayed. ASW on tetraploid L. multiflorum showed a reduced feeding response but no plant abandonment. These results reflected recent ASW parasitism rates that were low on the diploid host plants compared to those in the 1990s and may explain the behavioural mechanisms behind the biological decline. Similarly, behavioural responses to M. hyperodae differed between ASW regional populations, which reflected current parasitism ii rates and history. ASWs from the Waikato (Ruakura) region had the strongest behavioural responses to M. hyperodae where the greatest parasitism decline has occurred. There were delayed feeding reduction and plant abandonment responses to M. hyperodae from ASW populations (Canterbury: Lincoln; North of Auckland: Wellsford) with a medium decline in parasitism. There was minimal response from southern ASW populations (Otago: Invermay; Wiapiata) that have always had low parasitism rates with no decline detected. When comparing ASW responses to different parasitoid species, M. hyperodae showed the strongest responses with increased crouching and reduced feeding compared to other parasitoid species. There was some behavioural response to Microctonus aethiopoides (Hymenoptera: Braconidae), a parasitoid of the clover root weevil (Sitona obsoletus) (Coleoptera: Curculionidae), suggesting that ASW has pre-adaptation to this novel interaction. The findings in this work strongly suggest that ASW behavioural responses are the mechanism behind the potential contemporary evolution causing the parasitism decline. Future work could investigate the behavioural effects of M. hyperodae from different populations, and what cues ASW uses to detect M. hyperodae. Furthermore, identifying the underlying genetic or symbiont mechanism for the increased sensitivity of ASW behaviour is essential to confirm contemporary evolution, which would be novel in the literature. This work also has implications for the persistence of other long- term successful insect biological control systems and points to what factors may lead to their future decline in efficacy. Keywords: Asymmetric selection, Argentine stem weevil, behaviour, classical biological control, contemporary evolution, diffuse selection, feeding damage, Listronotus bonariensis, Lolium, microcosm, Microctonus hyperodae, natural enemies, non-consumptive effects, parasitoid, pasture, plant abandonment, ploidy, resistance, traits. iii Acknowledgements I am eternally grateful to my supervisors, Distinguished Professor Steve D. Wratten, Professor Stephen L. Goldson and my associate supervisor Dr Craig B. Phillips, for their guidance, knowledge, discussion and support. My deepest gratitude to my main supervisor, Steve Wratten: your patience, kindness, and invaluable mentoring have made this endeavour possible and created the foundation for my future development as an entomologist. I greatly appreciate the funding for this study provided by the Bio-Protection Research Centre and the Tertiary Education Commission of New Zealand (TEC) with a special acknowledgement to Stephen Goldson for facilitating the funding, for his leadership of the TEC Project 2 to which this study contributed to and for his guidance and unmatched knowledge of the study insects. There is also special thanks to Dr Chikako van Koten (AgResearch): your help and guidance in statistical analysis were fundamental to the completion of this work. I am immensely grateful to the casual research workers who helped me, Jacquelyn Bennett, Kate Scanlan, Malvika Bana, and the French interns Helena Minet, Olivier Lourme and Oceane Edely. Your enthusiasm and hard work was indispensable. Furthermore, you facilitated the development of my mentoring and management skills which I will always appreciate. I must also thank everyone at the Bio-Protection Research Centre and Lincoln University who helped me, such as Janine Johnson, Dr Will Godsoe, Dr Andrew Holyoake, Brian Kwan, and Dr Dave Savile. Colleagues in TEC Project 2 provided valuable discussion and guidance, such as Dr Paula Casanovas, Professor Peter Dearden, Professor Jason Tylianakis and Sarah Inwood. To my postgraduate friends in the Burns building at Lincoln University, I thank you for your discussions and support: Dr Shola Olaniyan, Sundar Tiwari, Dr Mauricio Gonzalez Chang, Dr Ryan Rayl, Dr Rowan Sprague, and Marie McDonald. I am grateful for the support and collaboration from colleagues at AgResearch, Dr Alison Popay, Dr Barbara Barratt, Colin Ferguson, Derick Wilson, Louise Hennessy, Mark McNeill, Dr Federico Tomasetto, Louise Winder and Dr Scott Hardwick for sampling insect material from around New Zealand and your discussions. The experiments conducted in this thesis would not have been possible without your help. I must acknowledge Dr Brian Patchett, Glen Jarvis and Tim Gillanders (CropMark Seeds Ltd) and Dr Alan Stewart (PGG Wrightson Ltd) for providing grass seed. I thank the Sutherlands, the Fishers and Francis Konin for allowing me to sample on their farms and the late Dr Rowan Emberson, Dr Peter Johns (Canterbury Museum) and Dr John Marris (Bio-Protection Research Centre) for identifying invertebrates for me. Lastly, I must also give special thanks to my family, particularly my amazing wife, Laura Shields, for your unwavering love, support, and sacrifice in order for me to complete this work. iv Table of Contents Host-parasitoid avoidance behaviour in the context of contemporary evolution in insect classical biological control ............................................................................................ 1 Abstract ........................................................................................................................ ii Acknowledgements ...................................................................................................... iv Table of Contents .......................................................................................................... v List of Tables ................................................................................................................. x List of Figures ............................................................................................................. xiii Chapter 1 Introduction ................................................................................................. 1 1.1 Global agriculture .....................................................................................................................1 1.2 Classical biological