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Causes and consequences of plasticity in parental and offspring behaviour in the burying beetle Nicrophorus vespilloides Tom Ratz A thesis submitted for the degree of Doctor of Philosophy University of Edinburgh 2020 Contents Declarations v Acknowledgements vii Lay Summary ix Abstract x Résumé vulgarisé xii 1 General Introduction 1 1.1 Plasticity in parental behaviour ....................... 5 1.1.1 Biparental behaviour ...................... 6 1.1.2 Plastic parental behaviour ................... 7 1.2 Plasticity in offspring behaviour ...................... 8 1.2.1 Plastic offspring behaviour ................... 9 1.3 Study System: Burying Beetle Nicrophorus vespilloides ............ 10 1.3.1 Parental and offspring behaviour in N. vespilloides ...... 12 1.3.2 Behavioural plasticity in N. vespilloides ............ 14 1.4 Aims .................................. 14 2 Parental response to increasing energetic costs 19 2.1 Introduction ............................... 20 2.2 Methods ................................. 23 2.2.1 Experimental design ...................... 23 2.2.2 Data analysis .......................... 29 2.3 Results ................................. 30 2.3.1 Female parental behaviour ................... 30 2.3.2 Offspring performance ..................... 31 2.3.3 Female investment in current and future reproduction .... 32 2.4 Discussion ................................ 35 i 3 Parental response to variation in energetic costs and brood size 42 3.1 Introduction ............................... 43 3.2 Methods ................................. 47 3.2.1 Experimental design ...................... 47 3.2.2 Handicapping procedure .................... 49 3.2.3 Female and offspring behaviours ................ 50 3.2.4 Female weight change and offspring performance ....... 51 3.2.5 Data analysis .......................... 52 3.3 Results ................................. 53 3.3.1 Female parental behaviour and weight change ........ 53 3.3.2 Offspring begging and performance .............. 54 3.4 Discussion ................................ 58 4 Parental response to infection 64 4.1 Introduction ............................... 64 4.2 Methods ................................. 68 4.2.1 Experimental design ...................... 68 4.2.2 Bacterial preparation ...................... 69 4.2.3 Infection procedure ....................... 70 4.2.4 Maternal care, female weight change, female mortality, and offspring performance ..................... 71 4.2.5 Hemolymph sampling, RNA extraction, and RT-qPCR .... 72 4.2.6 Data analysis .......................... 74 4.3 Results ................................. 75 4.4 Discussion ................................ 80 5 Biparental responses to resource availability 86 5.1 Introduction ............................... 87 5.2 Methods ................................. 91 5.2.1 Experimental design ...................... 91 5.2.2 Data analysis .......................... 93 5.3 Results ................................. 95 5.3.1 Duration of biparental care .................. 95 ii 5.3.2 Sex differences in duration of care ............... 95 5.3.3 Sex differences in amount of care ............... 98 5.3.4 Sex differences in carrion consumption and weight change .. 99 5.3.5 Offspring behaviour and performance ............. 99 5.4 Discussion ................................ 102 6 Offspring response to parental body size 107 6.1 Introduction ............................... 108 6.2 Methods ................................. 110 6.2.1 Experimental design ...................... 111 6.2.2 Larval behaviour ........................ 112 6.2.3 Data analysis .......................... 115 6.3 Results ................................. 116 6.4 Discussion ................................ 116 7 Effects of inbreeding on parent and offspring plasticity 122 7.1 Introduction ............................... 123 7.2 Methods ................................. 127 7.2.1 Larval behaviour ........................ 127 7.2.2 Parental behaviour ....................... 131 7.2.3 Data analysis .......................... 133 7.3 Results ................................. 134 7.3.1 Larval behaviour ........................ 134 7.3.2 Parental behaviour ....................... 135 7.4 Discussion ................................ 138 8 Effects of biparental care and inbreeding on offspring performance 143 8.1 Introduction ............................... 144 8.2 Methods ................................. 147 8.2.1 Experimental design ...................... 147 8.2.2 Data analysis .......................... 149 8.3 Results ................................. 150 8.3.1 Offspring fitness ........................ 150 8.3.2 Female and male weight gain ................. 151 iii 8.4 Discussion ................................ 154 9 General Discussion 159 9.1 Behavioural plasticity and parent-offspring interactions ............ 160 9.2 Implications for parental and offspring behaviour ............... 162 9.3 Implication for the study of behavioural plasticity .............. 166 9.4 Concluding remarks ............................ 168 References 169 Appendix: Journal articles arising from this thesis 202 A Ratz T, Nichol T, Smiseth PT (2020) Parental responses to increasing levels of handicapping in a burying beetle. Behavioral Ecology 31:73–80. B Ratz T, Smiseth PT (2018) Flexible parents: joint effects of handicap- ping and brood size manipulation on female parental care in Nicrophorus vespilloides. Journal of Evolutionary Biology 31:646–656. C Ratz T, Stenson S, Smiseth PT (2020) Offspring preferentially beg to- wards and associate with larger parents in the burying beetle Nicrophorus vespilloides. Behavioral Ecology, 31:1250–1256. D Ratz T, Perodaskalaki A, Moorad J, Smiseth PT (2020) Effects of inbreed- ing on behavioural plasticity of parent-offspring interactions in a burying beetle. Journal of Evolutionary Biology 33:1006–1016. E Ratz T, Castel E, Smiseth PT (2018) Male assistance in parental care does not buffer against detrimental effects of maternal inbreeding on offspring. Frontiers in Ecology and Evolution 6:196. iv Declarations This dissertation is submitted in accordance with the requirements for a Doc- torate of Philosophy by the School of Biological Sciences at the University of Edinburgh. The work included in this thesis has not been submitted for any other degree or professional qualification. I declare that I have written this thesis under the guidance of my supervisor. I conducted all experimental work with help as below. All other work was my own. Chapters 2: These experiments were designed with the help of my supervisor, Dr Per Smiseth. The majority of the data were collected by Thomas Nichol under my supervision. I performed all analyses presented here and wrote the subsequent manuscripts and chapter in collaboration with Dr Per Smiseth. Chapter 4: The data were collected and analysed in collaboration with Katy Monteith. I wrote the subsequent manuscript and chapter in collaboration with Dr Pedro Vale and Dr Per Smiseth. Chapter 5: The data were collected with Katerina Kremi and Lyndon Leissle. I performed all the analyses presented here and wrote the subsequent manuscript and chapter in collaboration with Dr Per Smiseth. Chapter 6: The majority of the data were collected by Sophie Stenson under my supervision. I performed all the analyses presented here and wrote the subsequent manuscript and chapter in collaboration with Dr Per Smiseth. Chapter 7: The data were collected in collaboration with Anastasia Perodaskalaki. I performed all the analyses presented here and wrote the subsequent manuscript and chapter in collaboration with Dr Jacob Moorad and Dr Per Smiseth. v Chapter 8: The data were collected in collaboration with Elise Castel. I per- formed all the analyses presented here and wrote the subsequent manuscript and chapter in collaboration with Dr Per Smiseth. Tom Ratz vi Acknowledgements A PhD is a little scientific journey, a human one too. I would like to thank all of those with whom I shared bits of this journey. The 4 years in the burying beetle lab have been illuminating and inspiring. I was very lucky to have a (super)-supervisor, Per Smiseth. Thank you so much Per for your endless support while putting together this thesis and your enthusiasm at each step. Many thanks to the past and present members of the lab for building such a supportive and friendly environment to work in: Lucy Ford, Matthieu Paquet, Ed Ivimey-Cook, Maarit Mäenpää, Charlotte Regan, Kynan Delaney, and Jon Richardson. I owe the success of many experiments to Jon, my academic twin, who has also been an unfailing lab/office mate. Thanks Jon for your daily cheerfulness! I wish to thank my postgraduate committee, Jacob Moorad and Sarah