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Fitness Consequences of Sex-Ratio Meiotic Drive and Female Multiple Mating in a Stalk-Eyed Fly, Teleopsis Dalmanni

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Fitness Consequences of Sex-Ratio Meiotic Drive and Female Multiple Mating in a Stalk-Eyed Fly, Teleopsis Dalmanni Fitness consequences of sex-ratio meiotic drive and female multiple mating in a stalk-eyed fly, Teleopsis dalmanni Lara Meade A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy of University College London. Department of Genetics, Evolution and Environment University College London May 17, 2018 1 I, Lara Meade, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the work. 2 Abstract Meiotic drive genes are a class of segregation distorter that gain a transmis- sion advantage in heterozygous males by causing degeneration of non-carrier sperm. This advantage must be balanced by fertility or viability costs if drive is to remain at stable frequencies in a population. A reduction in male fertility due to sperm destruction reduces the fitness of the rest of the genome, accordingly mechanisms to circumvent the effects of drive may evolve. Such adaptations will have implications for how likely it is that drive will persist. The primary theme of this thesis has been examining fertility consequences of meiotic drive in a Malaysian stalk-eyed fly, Teleopsis dalmanni. I demonstrate that drive carrier males are not sperm limited, despite the destruction of half their sperm. They produce ejaculates with sperm numbers equivalent to wildtype male ejaculates. Furthermore, drive males achieve this with greatly enlarged testes. However, resources are not unlimited; drive males also have reduced body size, and re- duced accessory glands and eyespan for their body size. Accessory gland size limits male mating frequency, and male eyespan is a sexually selected trait used in female choice and male-male competition. I discuss how these patters fit with theoretical models that predict males should invest in producing an optimal ejaculate according to levels of expected sperm competition, even if they are low-fertility males. A second interrelated theme of this thesis has been to examine the benefits of polyandry, female mating with multiple males, using wild-caught individuals. Polyandry is widespread across many taxa and almost ubiquitous in insects. However, there is much debate around its proximate and ultimate causes. There 3 are many costs associated with mating and so polyandry requires an adaptive explanation. I utilise data on wild-caught T. dalmanni to explore how natural variation amongst females and males influences fertility gains for females. 4 Acknowledgements With many thanks to my supervisors, Professor Pomiankowski and Professor Fowler, for their continuous support, advice and discussion. To the past and present Stalkie folk—Alison Cotton, Rebecca Finlay, Sam Finnegan, James Howie, and three excellent students Deidre Dinneen, Ridhima Kad and Dominic Lynch—as well as the Drosophila team—Mark Hill, Filip Ruzicka and Florencia Camus—working and chatting with you all was a privilege. A special thanks to my family, who are there for me always. Funding was provided by the Natural Environment Research Council (NERC). 5 Contents 1 Introductory Material 19 1.1 Overview . 19 1.2 Selfish Genetic Elements . 20 1.2.1 Meiotic drive . 21 1.2.2 Costs to fertility and viability of drive . 23 1.2.3 Sperm competition . 27 1.2.4 Meta-population dynamics . 27 1.2.5 Evolution of suppressors . 28 1.2.6 Drosophila simulans ..................... 29 1.3 Polyandry . 31 1.3.1 The evolution of polyandry as a female response to drive . 32 1.4 Stalk-eyed flies . 33 1.4.1 Teleopsis dalmanni ..................... 35 1.5 Structure of the thesis . 38 1.5.1 Chapter 2 . 38 1.5.2 Chapter 3 . 39 1.5.3 Chapter 4 . 39 1.5.4 Chapter 5 . 40 1.5.5 Chapter 6 . 40 1.5.6 Chapter 7 . 40 2 Adaptive maintenance of ejaculate size in the face of sperm destruc- tion by meiotic drive 42 6 2.1 Introduction . 44 2.2 Methods . 49 2.2.1 Stock source and maintenance . 49 2.2.2 Sperm in the spermathecae . 50 2.2.3 Sperm in the VR . 51 2.2.4 Sperm depletion . 51 2.2.5 Phenotyping and genotyping . 52 2.2.6 Statistical analysis . 53 2.3 Results . 55 2.3.1 Sperm in the spermathecae . 55 2.3.2 Sperm in the VR . 55 2.3.3 Sperm depletion . 57 2.3.4 Mating latency and mating duration . 58 2.4 Discussion . 58 2.5 Figures . 64 3 Adaptive compensation in fertility to meiotic drive in a stalk-eyed fly 67 3.1 Introduction . 69 3.2 Methods . 73 3.2.1 Stock source and maintenance . 73 3.2.2 Mating treatment . 74 3.2.3 Male reproductive organ size and fertility . 75 3.2.4 Genotyping . 76 3.2.5 Statistical analysis . 77 3.3 Results . 78 3.3.1 SR morphological and reproductive trait size . 78 3.3.2 SR fertility . 79 3.3.3 Reproductive trait size and fertility . 79 3.3.4 Fecundity . 80 3.4 Discussion . 80 3.5 Figures . 88 7 4 The use of microsatellite and INDEL markers to detect sex ratio mei- otic drive in Teleopsis dalmanni 95 4.1 Introduction . 97 4.2 Methods . 100 4.2.1 Wild males . 100 4.2.2 Laboratory males . 100 4.2.3 Phenotype assignment . 102 4.2.4 Genotyping . 103 4.2.5 Statistical analysis . 104 4.3 Results . 105 4.3.1 Wild males . 105 4.3.1.1 Brood sex-ratio and allele size in wild samples . 105 4.3.1.2 Male morphology, allele size and brood sex-ratio in wild samples . 107 4.3.1.3 Allele size consistency in wild samples . 107 4.3.1.4 Linear discriminant analysis . 108 4.3.1.5 Amplification . 108 4.3.2 Laboratory males . 108 4.3.2.1 Brood sex-ratio and allele size in laboratory sam- ples . 109 4.3.2.2 Male morphology, allele size and brood sex-ratio in laboratory samples . 110 4.3.2.3 Allele size consistency in laboratory samples . 111 4.3.2.4 Linear discriminant analysis . 111 4.3.2.5 Amplification . 112 4.4 Discussion . 112 4.5 Figures . 117 4.6 Tables . 120 5 Variation in the benefits of multiple mating on female fertility in wild stalk-eyed flies 122 8 5.1 Introduction . 124 5.2 Materials and Methods . 127 5.2.1 Experiment 1: Gains from an additional mating . 127 5.2.2 Experiment 2: Investigation of female and male effects . 128 5.2.3 Statistical analysis . 129 5.3 Results . 131 5.3.1 Experiment 1: Gains from an additional mating . 131 5.3.1.1 Variation in fecundity . 131 5.3.1.2 Variation in fertility . 132 5.3.2 Experiment 2: Investigation of female and male effects . 134 5.3.2.1 Variation in fecundity . 134 5.3.2.2 Variation in fertility . 134 5.4 Discussion . 135 5.5 Figures . 143 6 General Discussion 150 6.1 Overview . 150 6.2 Summary of findings . 151 6.2.1 Chapter 2: Adaptive maintenance of ejaculate size in the face of sperm destruction by meiotic drive . 151 6.2.2 Chapter 3: Adaptive compensation in fertility to meiotic drive in a stalk-eyed fly . 152 6.2.3 Chapter 4: The use of microsatellite and INDEL markers to detect sex ratio meiotic drive in Teleopsis dalmanni ... 154 6.2.4 Chapter 5: Variation in the benefits of multiple mating on female fertility in wild stalk-eyed flies . 155 6.3 Discussion . 156 6.4 Future directions . 162 6.4.1 Sperm competition and polyandry in Teleopsis dalmanni . 162 6.4.2 The effects of diet quality and variability on drive . 164 6.5 Conclusion . 165 9 Appendices 166 7 Appendices 166 A Chapter 2: Supplementary Information 167 A.1 Sperm in the spermathecae . 167 A.1.1 Sperm presence in the spermathcea . 167 A.1.1.1 Sperm presence in the spermathecae, including female size . 168 A.1.2 Sperm number in the spermathecae . 168 A.1.2.1 Sperm number in the spermathecae, including female size . 169 A.2 Sperm in the VR in the early period . 169 A.2.1 Sperm presence in the VR . 169 A.2.1.1 Sperm presence in the VR, including female size 170 A.2.2 Proportion of pouches filled in the VR . 170 A.2.2.1 Proportion of pouches filled in the VR, including female size . 171 A.3 Sperm in the VR in the late period . 172 A.3.1 Sperm presence in the VR . 172 A.3.1.1 Sperm presence in the VR, including female size 172 A.3.2 Proportion of pouches filled in the VR . 173 A.3.2.1 Proportion of pouches filled in the VR, including female size . 173 A.4 Sperm presence in the VR across early and late periods . 174 A.5 VR pouch number . 175 A.6 Sperm depletion . 175 A.6.1 Sperm presence in the spermathcea . 175 A.6.2 Sperm number in the spermathecae (across sequential matings) . 176 A.6.3 Sperm number in the spermathecae (across all matings) . 176 10 B Chapter 3: Supplementary Information 178 B.1 SR morphological and reproductive trait size . 178 B.1.1 Body size (thorax) . ..
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