MIAMI UNIVERSITY The Graduate School Certificate for Approving the Dissertation We hereby approve the Dissertation of Michael Sitvarin Candidate for the Degree: Doctor of Philosophy _________________________ Director Ann Rypstra _________________________ Reader Tom Crist _________________________ Reader Brian Keane _________________________ Reader Nancy Solomon _________________________ Graduate School Representative Dave Gorchov ABSTRACT BEHAVIORAL AND ECOLOGICAL CONSEQUENCES OF MULTIPLE INTRAGUILD PREDATORS AND CONNECTIONS BETWEEN PREDATORS, PREY, AND ECOSYSTEM FUNCTION by Michael I. Sitvarin Prey species sit at a pivotal point in food webs, serving as a connection between predators and energy sources (e.g., plants or detritus). Most prey face multiple predators and must integrate information about predation risk if they are to avoid being consumed. Meanwhile, predators interact with one another and can increase or decrease their combined pressure on prey. By interacting with their prey, predators can indirectly affect ecosystem functions, even without reducing prey population size. The goal of my dissertation was to understand how prey survive in a world with multiple predators and to uncover linkages between predators and the soil food web. I first tested hypotheses about how the wolf spider Pardosa milvina responds to cues from multiple predators (the larger wolf spider Tigrosa helluo and the ground beetle Scarites quadriceps) and how inaccurate information regarding predation threat affects survival. Pardosa were capable of distinguishing between predators and responding adaptively, though prey responses were not optimized when predators were at elevated hunger levels. As a second step, I allowed multiple predators (the wolf spider Rabidosa rabida along with Tigrosa and Scarites) to freely interact with each other and their prey (Pardosa) to test the influence of predator characteristics and the occurrence of intraguild predation on prey survival. Overall, I found support for a predictive framework of emergent multiple predator effects, though intraguild predation events caused significant deviations from model predictions. I also investigated the consumptive and nonconsumptive effects predators can have on their environment, focusing on the detrital food chain. The presence of either Pardosa or their cues impacted CO2 flux and soil nitrogen content as mediated by the detritivore Sinella curviseta, suggesting indirect top-down control of ecosystem function by predators. Finally, I tested the response of Sinella to cues indicating predation risk to determine if changes in detritivore activity linked predators to ecosystem function. Sinella responded innately to necromones but did not alter activity levels in the presence of Pardosa cues, even after a conditioning period. BEHAVIORAL AND ECOLOGICAL CONSEQUENCES OF MULTIPLE INTRAGUILD PREDATORS AND CONNECTIONS BETWEEN PREDATORS, PREY, AND ECOSYSTEM FUNCTION A DISSERTATION Submitted to the faculty of Miami University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Biology by Michael Ian Sitvarin Miami University Oxford, Ohio 2014 Dissertation Director: Ann L. Rypstra TABLE OF CONTENTS General Introduction........................................................................................................................1 Chapter 1: Patchy and Mismatched Cues: How Do Prey Respond To Multiple Predators Representing Different Levels of Risk?................................................................9 Abstract..............................................................................................................................10 Introduction........................................................................................................................11 Methods..............................................................................................................................13 Results................................................................................................................................16 Discussion..........................................................................................................................18 References..........................................................................................................................21 Tables & Figures …...........................................................................................................25 Chapter 2: The Importance of Intraguild Predation in Predicting Emergent Multiple Predator Effects....................................................................................................33 Abstract..............................................................................................................................34 Introduction........................................................................................................................35 Methods..............................................................................................................................37 Results................................................................................................................................41 Discussion..........................................................................................................................43 References..........................................................................................................................48 Tables & Figures …...........................................................................................................54 Chapter 3: Fear of Predation Alters Soil CO2 Flux and Nitrogen Content........................60 Abstract..............................................................................................................................61 Introduction........................................................................................................................62 Methods..............................................................................................................................63 Results................................................................................................................................64 Discussion..........................................................................................................................65 ii References..........................................................................................................................67 Tables & Figures …...........................................................................................................70 Chapter 4: Nonconsumptive Predator-Prey Interactions: Sensitivity of a Detritivore to Cues of Predation Risk........................................................................................74 Abstract..............................................................................................................................75 Introduction........................................................................................................................76 Methods..............................................................................................................................78 Results................................................................................................................................81 Discussion..........................................................................................................................83 References..........................................................................................................................86 Tables & Figures …...........................................................................................................91 General Conclusion and Future Directions....................................................................................99 References........................................................................................................................105 Appendix......................................................................................................................................107 Chapter 1: Supplementary Material.................................................................................108 Chapter 2: Supplementary Material.................................................................................109 Chapter 3: Supplementary Material.................................................................................113 Chapter 4: Supplementary Material.................................................................................129 iii LIST OF TABLES Chapter 1 Table 1. Loading of activities (from Videomex-V software) on principal components. Positive and negative values indicate positive and negative correlations with the principal component, respectively. Magnitudes indicate the strength of correlation between the activity variable and the principal component. Table 2. Effects of treatment (predator cues present in arena), predator hunger level, and their interaction on Pardosa activity. Model degrees of freedom: 7, 150. Table 3. Effects of treatment (predator cues present in arena) and predator hunger level on Pardosa activity. Statistics reported are Cohen's d, 95% confidence intervals, and F-values, degrees of freedom, and p-values from one-way ANOVAs. Treatments are blank (B), cues from Tigrosa (T), and cues from Scarites (S). Symbols between treatment letters indicate relationships based