Views See Kats and Dill; 1998; Dick and Grostal, 2001), While Predators Use Chemical Cues to Locate Prey (Koivula and Korpimaki, 2001)
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Miami University The Graduate School Certificate for Approving the Dissertation We hereby approve the Dissertation of Kerri M. Wrinn Candidate for the Degree: Doctor of Philosophy _______________________ Ann L. Rypstra, Advisor ________________________ Michelle D. Boone, Reader ________________________ Thomas O. Crist, Reader ________________________ Maria J. Gonzalez, Reader _________________________ David L. Gorchov Graduate School Representative ABSTRACT IMPACTS OF AN HERBICIDE AND PREDATOR CUES ON A GENERALIST PREDATOR IN AGRICULTURAL SYSTEMS by Kerri M. Wrinn Animals use chemical cues for signaling between species. However, anthropogenic chemicals can interrupt this natural chemical information flow, affecting predator- prey interactions. I explored how a glyphosate-based herbicide influenced the reactions of Pardosa milvina, a common wolf spider in agricultural systems, to its predators, the larger wolf spider, Hogna helluo and the carabid beetle, Scarites quadriceps. First, I tested the effects of exposure to herbicide and chemical cues from these predators on the activity, emigration, and survival of P. milvina in laboratory and mesocosm field experiments. In the presence of H. helluo cues in the laboratory, P. milvina always decreased activity and increased time to emigration. However, in the presence of S. quadriceps cues, these spiders only decreased activity and increased time to emigration when herbicide was also present. Presence of predator cues and herbicide did not affect the emigration of P. milvina from field mesocosms, but survival was highest for spiders exposed to S. quadriceps cues alone and lowest for those exposed to herbicide alone. Secondly, I tested the effects of predator cues, herbicide and prey availability on foraging and reproduction in female P. milvina. Spiders offered more prey captured and consumed more, while those exposed to H. helluo cues consumed less. Availability of prey and exposure to predator cues and herbicide in foraging trials had interactive effects on P. milvina’s subsequent reproductive success. In the low prey treatments, exposure to predator cues and herbicide each reduced reproductive success. In the high prey treatments, exposure to herbicide reduced reproductive success for spiders also exposed to S. quadriceps cues, but increased reproductive success for spiders also exposed to H. helluo cues. Finally, I exposed juvenile P. milvina to S. quadriceps cues and herbicide but found no effect of either on the spider’s growth and development. Together, these results indicate that predation risk and herbicide application likely interact in complex ways to affect the movement, reproduction and survival of a major arthropod predator in agricultural systems, and thus may have complex effects on the food web. IMPACTS OF AN HERBICIDE AND PREDATOR CUES ON A GENERALIST PREDATOR IN AGRICULTURAL SYSTEMS A DISSERTATION Submitted to the Faculty of Miami University in partial Fulfillment of the requirements for the degree of Doctor of Philosophy Department of Zoology by Kerri M. Wrinn Miami University Oxford, Ohio 2010 Advisor: Ann L. Rypstra Table of Contents Table of contents ii. List of Tables iv. List of Figures v. Acknowledgements vi. Chapter 1: General Introduction 1 Literature cited 4 Chapter 2: Predator cues and an herbicide impact activity, emigration and survival 10 in an agrobiont wolf spider Introduction 10 Methods 13 Collection and maintenance of animals 13 Herbicide preparation 13 Laboratory experiment 14 Field mesocosms 15 Results 17 Laboratory experiment 17 Field mesocosms 18 Discussion 18 Literature cited 23 Chapter 3: Effects of predator cues, prey level and an herbicide on reproduction in 35 Pardosa milvina (Araneae Lycosidae) Introduction 35 Methods 38 Animal collection and maintenance 38 Herbicide preparation 38 Collection of predator cues and application of herbicide 39 Exposure to chemical cues and foraging trials 39 Reproduction 39 Data analysis 40 Results 40 ii Foraging trials: Prey capture and consumption 40 Reproduction 41 Survival 42 Discussion 43 Foraging trials: Prey capture and consumption 43 Reproduction 44 Survival 46 Conclusions 48 Literature cited 50 Chapter 4: Exposure to herbicide and predator cues has no effect on growth, 62 development time, fluctuating asymmetry or survival in Pardosa milvina (Araneae: Lycosidae). Introduction 62 Methods 64 Animal care 64 Experimental design 65 Preparation and exposure to predator cues and herbicide 65 Data collection and analysis 66 Results 67 Growth, development time and survival 67 Fluctuating asymmetry 68 Discussion 68 Literature cited 72 Chapter 5: General conclusions and synthesis 81 Literature cited 86 Appendices 90 Appendix 90 iii List of Tables Table 2.1: The impacts of predator cues and/or herbicide on laboratory tests of 28 activity variables Table 2.2: Mean ± standard error of activity measures for P. milvina in response 29 to predator cues and/or herbicide or water Table 3.1: Mean ± standard error for number of crickets killed across treatments 55 Table 3.2: The effects of predator cues, herbicide and prey level on prey capture 56 and consumption Table 3.3: Tests for impacts of treatment on reproduction and survival in 57 P. milvina Table 4.1: Means ± standard error and Kruskal-Wallis results for measures of 76 growth between molts 3-4 Table 4.2: Means ± standard error and Kruskal-Wallis results for measures of 77 growth between molts 4-5 Table 4.3: Means ± standard error and Kruskal-Wallis results for measures of 78 growth between molts 5-6 Table 5.1: Effects of the stressors: predator cues, herbicide and prey availability 88 on the behavior and life history of P. milvina (Summary of Chapters 2-4) iv List of Figures Fig. 1.1: Presence of P. milvina and its intraguild predators H.helluo and 7 S. quadriceps in A. soy and B. corn fields. Fig. 1.2: Number of individuals captured in pitfall traps for three orders of prey 8 likely consumed by P. milvina in A. Soy and B. corn fields. Fig. 1.3: Outline of data chapters: Potential impacts of herbicide and predator 9 cues on different behaviors and life stages of P. milvina. Fig. 2.1: Laboratory arena for exposing Pardosa milvina to herbicide and/or 30 predator cues. Fig. 2.2: Field mesocosm for testing emigration of Pardosa milvina in response 31 to herbicide and/or S. quadriceps cues. Fig. 2.3: Activity of Pardosa milvina when exposed to herbicide or water and/or 32 predator cues in 15 minute laboratory trials. Fig. 2.4: Proportion of spiders remaining in the container over time for P. milvina 33 exposed to predator cues and/or herbicide or water in 15 minute laboratory trials. Fig. 2.5: Survival over a 60 day period of P. milvina after being subjected to 34 S. quadriceps cues, herbicide, neither, or both for 24 hours. Fig. 3.1: Fully factorial experimental design for the effects of Predator cues, 58 herbicide, and prey availability on foraging and reproduction in P. milvina. Fig. 3.2: Abdomen width change in P. milvina after foraging for two hours on 59 crickets during exposure to predator cues and/or herbicide. Fig. 3.3: Reproduction by P. milvina after exposure to predator cues and 60 herbicide. Fig. 3.4: Proportion of adult P. milvina surviving over a 60 day period after 61 exposure to predator cues and herbicide. Fig. 4.1: Diagram of the container in which juvenile Pardosa milvina were exposed 79 to Scarites quadriceps cues and/or glyphosate-based herbicide for 24 hours. Fig. 4.2: Relationship between the absolute value of fluctuating asymmetry (FA) of 80 Patella-tibia length and Cephalothorax width in adult Pardosa milvina. Fig. 5.1: Number of adult female, adult male and juvenile P. milvina collected in 89 dry pitfall traps over a 24 hour period from A. soy and B. corn fields. v Acknowledgements I would never have been able to complete my dissertation without the support of many people. I would like to thank my advisor, Ann Rypstra for guiding me through the doctoral process from start to finish with plenty of advice and encouragement. I would also like to express my gratitude to my committee, Michelle Boone, Tom Crist, Maria Gonzalez, and Dave Gorchov for their aid in designing, analyzing and writing up my work. I am grateful to my lab mates Chad Hoefler, Jen Riem, Shawn Wilder, Jason Schmidt, and Michael Sitvarin for their support in helping me with fieldwork, reading drafts of my chapters or just giving me an encouraging word. I appreciate the assistance of the multitude of undergraduate students that contributed to my research through their help in the lab and field and by providing comments on my papers during lab meetings over the years. I would like to express special thanks to Sam Evans, Chris Carter and Sandra Rittman; I definitely couldn’t have completed my experiments without them! I would also like to acknowledge the other graduate students and post docs who offered their friendship and support including: Makiri Sei, Gary Gerald, Lisette Torres, Molly Steinwald, Adrian Chesh, Rick Seidel, and many others. I am grateful to my family and non science friends who never failed to support me in my obsession with arachnids. Finally, I want to thank my husband Todd Levine, for supporting me both personally and professionally throughout the Ph.D process and Cassie, our daughter to be, for giving me a reason to finish my dissertation on time! For financial support I thank Miami University and the Zoology department. vi Chapter 1: General Introduction The process of detection and response to chemical cues plays a critical role in the lives of animals across various ecosystems. Chemical cues are particularly important in predator- prey interactions; prey recognize inter-specific chemical cues and avoid them to evade predators (for reviews see Kats and Dill; 1998; Dick and Grostal, 2001), while predators use chemical cues to locate prey (Koivula and Korpimaki, 2001). Therefore, failure of animals to detect these natural chemical cues could disrupt predator-prey interactions, with impacts at both the population and community levels.