Life-History Evolution in the Parasitoid Wasp Nasonia Vitripennis
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Life-history evolution in the parasitoid wasp Nasonia vitripennis by Edward Mathison Sykes Submitted for the Degree of Doctor of Philosophy The University of Edinburgh 2007 Contents List of Figures…………………………………………………………………………….5 List of Tables……………………………………………………………………………..5 Declaration……………………………………………………………………………….6 Acknowledgments………………………………………………………………………..7 Abstract ………………………………………………………………………………….8 Chapter 1 . General Introduction………………………………………………………...9 1.1 The use of parasitoids and Nasonia vitripennis ………………………………...10 1.2 Thesis plan……………………………………………………………………...14 1.3 Clutch size theory……………………………………………………………....15 1.3.1 Host quality……………………………………………………………...15 1.3.2 Time, host and egg-limited……………………………………………...16 1.3.3 Host-feeding……………………………………………………………..18 1.3.4 Maternal condition and ovigeny index (OI)……………………………..19 1.3.5 Superparasitism………………………………………………………….20 1.4 Sex allocation theory…………………………………………………………....21 1.4.1 Relatedness………………………………………………………………21 1.4.2 Local mate competition (LMC)………………………………………….22 1.4.3 Host quality and asymmetric larval competition (ALC)…………………23 1.5 Discussion……………………………………………………………………….24 Chapter 2. Relating body size to female fitness………………………………………...25 2.1 Abstract………………………………………………………………………….25 2.2 Introduction……………………………………………………………………...26 2.3 Methods…………………………………………………………………………27 2.3.1 Study organism…………………………………………………………..27 2.3.2 Laboratory stock…………………………………………………………28 2.3.3 Experimental design……………………………………………………..29 2.3.4 Analysis…………………………………………………………………..31 2.4 Results…………………………………………………………………………...32 2.4.1 Brood size, body size and sex ratio………………………………………32 2.4.2 Body size and female starvation resistance………………………………34 2.4.3 Body size and female reproductive lifespan……………………………..34 2.4.4 Body size and lifetime female fecundity…………………………………37 2.4.5 Body size and female fecundity over time……………………………….38 2.4.6 Body size and sex allocation……………………………………………..40 2.5 Discussion……………………………………………………………………….40 Chapter 3. Relating body size to male fitness…………………………………………..43 3.1 Abstract………………………………………………………………………….43 2 3.2 Introduction……………………………………………………………………44 3.3 Methods……………………………………………………………………….45 3.3.1 Study organism…………………………………………………………..45 3.3.2 Experimental strains and maintenance…………………………………..47 3.3.3 Experiment on size and mating success………………………………….48 3.3.4 Experiment on size and mating success in competition………………….49 3.3.5 Experiment on size, lifetime mating success and the cost of mating…….49 3.3.6 Statistical analyses……………………………………………………….50 3.4 Results…………………………………………………………………………...52 3.4.1 Experiment on size and mating success………………………………….52 3.4.2 Experiment on size and mating success in competition………………….53 3.4.3 Experiment on size, lifetime mating success and the cost of mating…….54 3.5 Discussion……………………………………………………………………….56 Chapter 4. The role of asymmetric larval competition………………………………….60 4.1 Abstract………………………………………………………………………….60 4.2 Introduction……………………………………………………………………...61 4.3 Methods…………………………………………………………………………62 4.3.1 Study organism…………………………………………………………..62 4.3.2 Laboratory stock…………………………………………………………63 4.3.3 Experimental design……………………………………………………..63 4.3.4 Testing for asymmetric larval competition ……………………………...64 4.3.5 Analysis…………………………………………………………………..65 4.4 Results…………………………………………………………………………..66 4.4.1 Competition and body size……………………………………………….66 4.4.2 Competition and longevity……………………………………………….68 4.4.3 Competition and lifetime fecundity……………………………………...69 4.5 Discussion and Appendix……………………………………………………….70 Chapter 5. Inbreeding depression and Nasonia vitripennis ……………………………..77 5.1 Abstract………………………………………………………………………….77 5.2 Introduction……………………………………………………………………..78 5.3 Method…………………………………………………………………………..79 5.3.1 Study organism…………………………………………………………..79 5.3.2 Inbred lines……………………………………………………………….80 5.3.3 Creating the crosses……………………………………………………...80 5.3.4 Offspring fitness………………………………………………………….81 5.3.5 Analysis…………………………………………………………………..81 5.4 Results…………………………………………………………………………...82 5.4.1 The effect of inbreeding on time to eclosion…………………………….82 3 5.4.2 The effect of inbreeding on longevity………………………………….84 5.4.3 The effect of inbreeding on fecundity………………………………….86 5.5 Discussion……………………………………………………………………….87 Chapter 6. General Discussion………………………………………………………….90 6.1 Clutch size theory……………………………………………………………….90 6.2 Sex allocation theory……………………………………………………………93 6.3 Inbreeding depression…………………………………………………………...97 6.4 Concluding remarks……………………………………………………………..97 Bibliography …………………………………………………………………………….98 Appendices ……………………………………………………………………………..111 4 List of Figures Figure 2-1. Experimental method for relating body size to female fitness……………..29 Figure 2-2. The relationship between larval competition and body size………………...33 Figure 2-3. The relationship between female starvation resistance and a) body size b)..35 larval competition c) clutch sex ratio Figure 2-4. The relationship between larval competition and fecundity………………...37 Figure 2-5. The relationship between reproductive investment and age………………...38 Figure 2-6. The relationship between larval competition and future clutch sizes……….39 Figure 3-1. Insemination success of solitary males……………………………………...52 Figure 3-2. The relationship between insemination success and male size……………...53 Figure 3-3. The effect of mating on longevity…………………………………………..55 Figure 3-4. The relationship between male size and total number of females…………..56 inseminated Figure 4-1. The relationships between larval competition and male and female size…...67 Figure 4-2. The interaction between larval competition and sex ratio affects female…...68 body size Figure 4-3. The relationship between body size and longevity………………………….69 Figure 4-4. The correlation between larval competition and lifetime fecundity………...70 Figure 4-5. Predicted consequences of asymmetric larval competition for offspring…..72 sex ratio in Nasonia vitripennis Figure 4-6. Predicted consequences of asymmetric larval competition for offspring…..74 sex ratio in Bracon hebetor Figure 5-1. Relationship between maternal genotype and development time…………...83 Figure 5-2. Relationship between genotype and development time at 18°C…………….84 Figure 5-3. Relationship between maternal genotype and adult longevity……………....85 Figure 5-4. Interaction between female zyogsity and maternal genotype and how……..85 it affects adult longevity Figure 5-5. Interaction between female zyogsity and maternal genotype and how……..87 it affects fecundity List of Tables Table 2-1. Variation in experimental brood size, sex ratio and body size………………32 Table 4-1. The mean clutch sizes and sex ratios produced in treatment broods from…..69 varying numbers of mated and virgin foundresses Table 4-2. Parameters used to create a model of asymmetric larval competition……….71 5 Declaration I declare that this thesis is entirely my own work, except for the collaborations mentioned below: Chapter 3: The first two of the three experiments were created and carried out by Maxwell Burton. I had sole responsibility for my experiment and we wrote the resulting manuscript together. Chapter 4: The mathematical modelling and associated figures (4-5 and 4-6) are the work of Ido Pen. Chapter 5: The inbreeding experiment was set up by Kathleen Reynolds. I then gathered and analysed the data. The wasp drawings in Figure 2-1 were created by Ana Rivero. 6 Acknowledgments This is the part where I try and thank everyone that has helped me to finish my thesis. Unfortunately, I know that I can’t do them justice. Without their help, in all its myriad of forms, I would not have even come close to finishing. First and ultimately, my supervisor Stu West was always able to put me back on track. His ability to simultaneously see the bigger picture and focus on the key points in my waffle was priceless. Secondly, Dave Shuker whether offering me a fresh idea or a nudge in the right direction was always persevering, perhaps in vain, to teach me how to think and I am extremely grateful. However, I wouldn’t even have been in the position to need their help if it weren’t for the vital funding that NERC so generously gave me. During the four years that I was involved with The Westgroup and everyone at IEB, I had the chance to work and play with a fantastic bunch of people, in particular: Tabi Innocent, the gift-seeker and motivator extraordinaire; Stu Killick, the Panto Gimp and both Aleta Graham and Gav Ballantyne who kept me sane in the lab when, by all rights, I should have gone completely mad. At this point, I should also give a mention, though they’ll never know it, to J.K. Rowling and Stephen Fry, for even if some people didn’t appreciate their genius, it certainly kept me going! I was also lucky enough to have the joys of running across the hail-strewn, crater-pitted snow fields of Jack Kane with Sporting ICAPB (the world’s greatest football team to field evolutionary biologists) and diving some of the best (and worst!) sites in Britain and Oman with EUSAC and Project NEMO. When my funding stopped in my fourth year it was actually a blessing in disguise as it meant that I was able to meet and work with everyone from the hideously- named, but wonderfully-fun Scottish Initiative for Biotechnology Education. There I was able to indulge in one of my favourite past-times, the act of communicating science to others, completely forgetting the overshadowing PhD five mornings per week – until of course Lara Crossland and the others sent me to the library. I need to make a special