W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 2003 A theoretical and experimental study of Allee effects Joanna Gascoigne College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Ecology and Evolutionary Biology Commons, Fresh Water Studies Commons, and the Oceanography Commons Recommended Citation Gascoigne, Joanna, "A theoretical and experimental study of Allee effects" (2003). Dissertations, Theses, and Masters Projects. Paper 1539616659. https://dx.doi.org/doi:10.25773/v5-qwvk-b742 This Dissertation is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. A THEORETICAL AND EXPERIMENTAL STUDY OF ALLEE EFFECTS A Dissertation Presented to The Faculty of the School of Marine Science The College of William and Mary in Virginia In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Joanna Gascoigne 2003 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPROVAL SHEET This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Joanna/Gascoigne Approved August 2003 Romuald N. Lipcius"Ph.D. Committee Chairman/Advisor L Rogar Mann, Ph.D. Mark R. Patterson, Ph.D. 1 Shandelle M. Henson, Ph.D Andrews University Berrien Springs, MI Callum Roberts, Ph.D. University of York, UK Craig Dahlgren, Ph.D. Caribbean Marine Research Centre Perry Institute for Marine Science Lee Stocking Island, Bahamas / Jupiter, FL Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPROVAL SHEET This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Joanna Gascoigne Approved August 2003 Romuald N. Lipcius, Ph.D. Committee Chairman/Advisor Roger Mann, Ph.D. Mark R. Patterson, Ph.D. Shandelle M. Henson, Ph.D. Andrews University Berrien Springs, MI Callum Roberts, Ph.D. University of York. UK Craig Dahlgren, Ph.D., Caribbean Marine Research Centre Perry Institute for Marine Science Lee Stocking Island, Bahamas / Jupiter, FL Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. To my family iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ACKNOWLEDGEMENTS..........................................................................................viii ABSTRACT.................................................................................................................. ix CHAPTER 1: ALLEE EFFECTS IN MARINE SYSTEMS......................................2 ABSTRACT..................................................................................................... 3 INTRODUCTION -..................................................................................... 4 What are Allee effects?............... -........................................................ 4 Are Allee effects likely in marine systems? ....................................... 5 Allee effects and human impacts on marine systems........................ 6 MODEL DESCRIPTION................................................................................ 8 MODEL RESULTS......................................................................................... 10 EMPIRICAL EVIDENCE...................................................................... -......... 11 Broadcast spawners..............................................................................12 Reproduction in non-broadcast spawners...........................................15 Survival-related Allee effects..............................................................17 Demographic Allee effects.................................................................. 19 CONCLUSIONS.............................................................................................. 20 REFERENCES................................................................................................. 23 TABLES............................................................................................................29 FIGURES.......................................................................................................... 30 CHAPTER 2: POPULATION CONSEQUENCES OF ALLEE EFFECTS IN REPRODUCTION AND SURVIVAL IN RELATION TO LIFE HISTORY- 40 ABSTRACT..................................................................................................... 41 INTRODUCTION-........................................................................................... 43 METHODS....................................................................................................... 46 Model description................. 46 Model runs........................................................................................... 49 Analysis of equilibria .......................................................................... 51 RESULTS......................................................................................................... 52 Dynamics with one Allee effect only.................................................52 Effects of density-independent parameter values..............................55 Adding negative density dependence to Allee effects.......................57 Combining both types of Allee effect ................................................59 Analysis of equilibria ..........................................................................60 DISCUSSION..................................................................................................61 Qualitative dynamics...........................................................................61 Which type of Allee effect is worse?..................................................62 Adding Allee effects together.............................................................64 Effect of negative density dependence-.............................................. 65 Effect of human disturbance ............................................................... 65 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Resilience in populations and ecosystems...........................................69 REFERENCES..................................................................................................71 TABLES............................................................................................................. 75 FIGURES........................................................................................................... 79 CHAPTER 3: ALLEE EFFECTS IN QUEEN CONCH REPRODUCTIVE BEHAVIOUR: FIELD TEST AND THEORETICAL CONSEQUENCES.............. 109 ABSTRACT...................................................................................................... 110 INTRODUCTION-............................................................................................ I l l METHODS.........................................................................................................116 Site characteristics and surveys............................................................ 116 Experimental design............................................................................. 117 Morphological data-.............................................................................. 118 Data analysis..........................................................................................118 Modelling.............................................................................................. 120 RESULTS...........................................................................................................123 Matings and reproductive index...........................................................123 Sex ratio................................................................................................ 124 Shell morphological and reproductive anatomy................................. 125 Condition and resource allocation to reproduction-............................ 125 Modelling.............................................................................................. 126 DISCUSSION-................................................................................................... 126 REFERENCES.................................................................................................. 132 TABLES............................................................................................................. 135 FIGURES........................................................................................................... 138 CHAPTER 4: PREDATOR-DRIVEN ALLEE EFFECTS: THEORETICAL FRAMEWORK AND EMPIRICAL EVIDENCE -............ ...................................... 147 ABSTRACT...................................................................................................... 148 INTRODUCTION............................................................................................ 149 The Allee effect.................................................................................... 149 Component Allee effects: reproduction vs. survival.......................... 150 Predator functional response