Open Research Online The Open University’s repository of research publications and other research outputs An individual based population study of an insect herbivore (Urophora jaceana) and its host plant (Centaurea nigra) Thesis How to cite: Paul, Roger Philip (1998). An individual based population study of an insect herbivore (Urophora jaceana) and its host plant (Centaurea nigra). PhD thesis The Open University. For guidance on citations see FAQs. c 1997 Roger Philip Paul https://creativecommons.org/licenses/by-nc-nd/4.0/ Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.0000fe91 Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk U (\/l2bS7RlCT^ A x y . IndivlcSLiaâl based £>0£>\alat:lozl study of an Ixxsect herbivore C ZJ’jro£>Jnojr& CG&n a*) and its host plant C ta urea grra) . Roger Philip Paul M.A. (Cantab) Thesis submitted for the degree of Doctor of Philosophy of the Open University, U.K. Discipline: Biology 17th May 1997 Preferred citation: Paul R.P. (1997) An mdividual based population study of an insect h e rb iv o re {Urophora jaceana) and its host plant {C e n ta u re a n ig ra ). Ph.D. Thesis, The Open University, U.K. ProQuest Number: 27696830 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 27696830 Published by ProQuest LLO (2019). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLO. ProQuest LLO. 789 East Eisenhower Parkway P.Q. Box 1346 Ann Arbor, Ml 48106- 1346 Paul, R.P. (1997) An individual based population study of an insect h e rb iv o re {Urophora jaceana) and its host plant {Centaurea nigra), Ph.D. Thesis, The Open University, U.K. Abstract - Urophora jaceana Bering (Diptera; Tephritidae) is a gall-forming insect of the capitula of Centaurea nigra L. (Compositae). Oviposition occurs at an early stage of flowerbud development. The aim of this thesis is to relate population processes of regulation of fly numbers and phenotypic selection on plant characters to aspects of individual behaviour of Urophàra jaceana, through the development of a Dynamic State Variable Model of female fly oviposition choices. The dynamic model incorporates larval survival functions obtained experimentally, and foraging time budgets estimated from field observations. The model predicts clutch size and super-oviposition at varying egg-loads, age, and host density. Super-oviposition is more likely at low encounter rates with flowerheads, and this prediction was tested experimentally and found to hold. Using a Monte Carlo Simulation, competition for ovipoation sites, and the inverse dependence of larval survival on clutch size at high egg densities, emerge as the most likely regulating factors of fly numbers. The effect of gall infestation on plants was found to be limited to reducing seed production. No density dependent regulation of fly density was discovered by k-factor analysis in the gall formation to pupal phase of the life cycle. The intensity of gall infestation was found to be inversely dependent on day of budding of flowerbuds, and relates to resource availability. Measuring the intensity of selection on three plant characters revealed that gall infestation exerts a directional selection pressure on the day of budding of plants. A simple heritability test suggests that there is an evolutionary response to selection. C o n te n ts O o n - t e n t i s Part 1: Introduction 1 Chapter 1: Individuals and populations 3 Chapter 2: Organisms, Field Study Site and Methods 7 2.1 Organisms: Centaurea nigra L. Compositae 7 2.1.1 Taxonomy 7 2.1.2 Phenology 8 2.1.3 Vegetative reproduction 9 2.1.4 Sexual reproduction 9 2.1.5 Mortality 10 2.2 Organisms: Urophora jaceana 11 2.2.1 Taxonomyc 11 2.2.2 Life history 11 2.2.3 Natural enemies: Parasitoids 1^ 2.2.4 Natural enemies: Lepidoptera 17 2.3 The field study site 19 2.4 General methods used in the thesis 23 2.4.1 Fieldwork methods 23 2.4.2 Dissection of flowerbuds 23 2.4.3 Dissection of galls 24 2.4.4 Handling adult gall flies 25 2.4.5 Statistical methods 26 C o n te n ts 11 Part 2: Individual Behaviour and Dynamic Modelling 31 Chapter 3: The principles of Dynamic State Variable Modelling 33 Chapter 4: Search and Foraging Behaviour of female Urophora jaceana 4 1 4.1 Factors which influence search and foraging behaviour 4 1 4.2 Search and oviposition behaviour of fem ale Urophora jaceana 46 4.2.1 Method 4 7 4.2.2 Results 4 s 4.2.3 Discussion 56 Chapter 5: Which flowerbud hosts are accepted for oviposition? 5 9 5.1 Oviposition strategy 5 g 5 .2 M e th o d 5 1 5.3 Results and analysis 64 5.4 Discussion 5 / Chapter 6: Clutch Size and Larval Mortality 6 9 6.1 Clutch size in insect life history strategy 69 6.1.1 The Lack Solution Clutch Size 69 6.1.2 Clutch Size in insects 69 6.1.3 Host quality and fitness 7 3 6.1.4 Methodological problems 7 4 C o n te n ts i ü 6.2 Mortality of Urophora jaceana eggs and larvae before gall formation 77 6.2.1 Introduction 77 6.2.2 Method 79 6.2.3 Results 80 6.2.4 Discussion 89 6.3 The survival of gall fly larvae from gall formation up to third instar 93 6é3.1 Introduction 93 6.3.2 Method 95 6.3.3 Results 96 6.3.4 Discussion 104 Chapter 7: A Dynamic Model for Urophora jaceana ovipositing in flowerheads of Centaurea nigra 107 7.1 Developing the Model 107 7.1.1 The Dynamic Modelling Equation 107 7.1.2 Solving the Dynamic Modelling Equation 119 1.2 Predictions of the Model Concerning Optimal Behaviour of Individuals 123 7.2.1 Introduction 123 7.2.2 Method 124 7.2.3 Results 126 7.2.4 Predictions of the Dynamic Modelling Equation about individual behaviour 132 7.2.5 Discussion 134 C o n te n ts - iv 7.3 Testing the model: Superoviposition in relation to the frequency of encountering a host 137 7.3.1 Introduction 137 7.3.2 Method 139 7.3.3 Results 143 7.3.4 Discussion 150 Chapter 8: The Population Consequences of individual Behaviour of Gall F lie s 153 8.1 Introduction 153 8.2 Method 15p 8.3 Results 156 8.4 Discussion 163 Part 3: Individual Differences and Population Level Phenomena 167 Chapter 9: Effects of Gall-Xnfestation on Centaurea nigra 169 9.1 The effect of gall-infestation on individual plants 169 9.1.1 Introduction 169 9.1.2 Materials and methods 172 9.1.3 Statistical analysis 175 9.1.4 Results 177 9.1.5 Discussion 192 C o n te n ts v 9,2 The effect of the insect herbivore on plant population dynamics: seed production and seedling density 197 9.2.1 Introduction 197 9.2.2 Method 198 9.3.3 Results 201 9.2.4 Discussion 208 Chapter 10: The Regulation of Gall Fly Population by Natural Enemies 211 10.1 Introduction 211 10.2 Methods 214 10.3 Results 217 10.4 Discussion 227 Chapter 11: The within-Season variation of Resource Availability, Gall Density and Larval Survival 231 11.1 Introduction 231 11.2 Methods 233 11.3 Results 236 11.4 Discussion 242 Chapter 12: Phenotypic variation and selection of Centaurea nigra 247 12.1 The measurement of selection on characters of Centaurea nigra due to gall infestation by U ro p h o ra ja c e a n a 247 12.1.1 Introduction 247 VI C o n te n ts 255 12.1.2 Method 255 12.1.3 Results Î2J.4 Discussion 12.2 To investigate the heritability of phenotypic 267 characters of Centaurea nigra 2 67 12.2.1 Introduction 272 12.2.2 Method 273 12.2.3 S tatistical analysis 274 12.2.4 Results 278 12.2.5 Discussiçn 281 Part 4: Conclusion Chapter 13i From liiaivldual Behaviour to Population 283 Level Phenomena 13.1 Timing of Oviposition 283 13.2 Regulation of Gall Fly Populations 283 13.3 Selection on day of budding of the plant as a result of gall infestation 13.4 The Dynamic State Variable Model 287 293 References 313 Appendix: Compute Programme of Dynamic Model List of tables V ll List of Tables Table 1: Chalcideidae parasitoids attacking larvae and pupae of Urophora jaceana^ after Varley (1947) 13 Table 2.1: Key to Plate 2. 14 Table 2.2: Key to Plate 3. 16 Table 3: IWative abundance of plants in two plots in the fW d study s ite . 20 Table 4: General form of the Analysis of Variance Table. 27 Table 5: General form of Analysis of Deviance table with Poisson and Bincmdal error structure.