University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2008 THE ROLE OF SPIDERS IN THE DETRITAL FOOD WEB OF AN EASTERN DECIDUOUS FOREST Erin Elizabeth Hladilek University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Hladilek, Erin Elizabeth, "THE ROLE OF SPIDERS IN THE DETRITAL FOOD WEB OF AN EASTERN DECIDUOUS FOREST" (2008). University of Kentucky Doctoral Dissertations. 682. https://uknowledge.uky.edu/gradschool_diss/682 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF DISSERTATION Erin Elizabeth Hladilek The Graduate School University of Kentucky 2009 THE ROLE OF SPIDERS IN THE DETRITAL FOOD WEB OF AN EASTERN DECIDUOUS FOREST ________________________________________ ABSTRACT OF DISSERTATION ________________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Agriculture at the University of Kentucky By Erin Elizabeth Hladilek Lexington, KY Co-directors: Dr. Mary Arthur, Professor of Forestry and Dr. John Obrycki, Professor of Entomology Lexington, KY 2009 Copyright © Erin Elizabeth Hladilek 2009 ABSTRACT OF DISSERTATION THE ROLE OF SPIDERS IN THE DETRITAL FOOD WEB OF AN EASTERN DECIDUOUS FOREST Historically, terrestrial food web research has focused on describing the structure of aboveground grazing webs, and determining how interactions among plants, herbivores and higher trophic levels influence primary productivity. Detrital food webs however, play a significant role in regulation of ecosystem dynamics through direct impacts on decomposition. Unraveling the complex nature of detrital food web structure is critical to developing a better understanding of ecosystem function. Therefore the primary objective of this research was to describe the structure of the leaf-litter food web in a temperate deciduous forest, with emphasis on interactions between a community of generalist predators, the forest-floor spiders, and arthropod prey. Elucidating occurrence of trophic interactions in the forest-floor food web was a formidable task due to the high diversity, small body sizes and cryptic habits of many litter-dwelling arthropods. Analysis of natural variation in consumer stable isotope ratios (δ13C and δ15N) formed the crux of this research because it simultaneously permitted quantification of the trophic positions of litter- dwelling arthropods and identification of spider resources, including prey subsidies from the grazing web. A monoclonal antibody-based ELISA was employed to analyze the gut contents of spiders to quantify predation on a major arthropod taxon, the forest-floor flies. Surveys of spider distributions and prey availability in the litter layer also provided fundamental knowledge of community structure. Stable isotope analyses suggested that most spiders exhibited strong trophic connections to the detrital web, but weak links to herbivorous prey. Several lines of evidence supported a strong trophic link between large, litter- dwelling collembolans (Tomoceridae) and cursorial spiders, including correlation between spider and tomocerid densities on the forest-floor, similarities in spider and tomocerid carbon signatures, and nitrogen enrichment of tomocerids relative to other prey types. Conversely, this research provided conflicting evidence regarding spider consumption of flies. Gut content assays indicated consistent predation on flies by cursorial spiders, while stable isotope models suggested that flies are likely of little importance in the spiders’ diets. This project yielded valuable insights into the role of spiders in the forest-floor food web and the potential importance of species-specific variation in prey consumption for detrital food web dynamics. KEYWORDS: stable isotope analysis, gut content analysis, monoclonal antibody-based ELISA, Diptera, Collembola Erin E. Hladilek Student’s signature December 22, 2008 Date THE ROLE OF SPIDERS IN THE DETRITAL FOOD WEB OF AN EASTERN DECIDUOUS FOREST By Erin Elizabeth Hladilek Dr. Mary Arthur Co-Director of Dissertation Dr. John Obrycki Co-Director of Dissertation Dr. Ken Yeargan Director of Graduate Studies December 22, 2008 RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor's degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the dissertation in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. Name Date ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ DISSERTATION Erin Elizabeth Hladilek The Graduate School University of Kentucky 2009 THE ROLE OF SPIDERS IN THE DETRITAL FOOD WEB OF AN EASTERN DECIDUOUS FOREST ________________________________________ DISSERTATION ________________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Agriculture at the University of Kentucky By Erin Elizabeth Hladilek Lexington, KY Co-directors: Dr. Mary Arthur, Professor of Forestry and Dr. John Obrycki, Professor of Entomology Lexington, KY Copyright © Erin Elizabeth Hladilek 2009 ACKNOWLEDGEMENTS I would like to acknowledge the contributions of several individuals that have been instrumental in providing guidance and support during the course of my doctoral program. Firstly, I would like to thank the co-directors of my dissertation, Dr. Mary Arthur and Dr. John Obrycki, who provided me with invaluable advice and devoted considerable effort to ensuring the successful completion of this research. Second, I would like to thank the members of my academic advisory committee Dr. James Harwood, Dr. Lynne Rieske-Kinney and Dr. David Wise, for providing insight and helpful suggestions. In particular, I would like to acknowledge the collaborative efforts of James Harwood, who contributed the monoclonal antibody used in this project, kindly allowed me to work in his lab, and provided technical expertise. This research was originally conceived and developed in the lab of David Wise, who has provided extensive support and advice. Finally I would like to acknowledge UK Department of Entomology, which provided support for this project, and the Forestry Department at Berea College for use of the Berea College Forest as a study site. iii TABLE OF CONTENTS Acknowledgements ..............................................................................................iii List of tables .........................................................................................................vi List of figures .......................................................................................................vii Chapter I: Introduction Research summary........................................................................................... 1 Study site description........................................................................................ 5 Chapter II: Leaf-litter spider community composition and microhabitat associations Summary........................................................................................................... 6 Introduction ....................................................................................................... 7 Materials and methods...................................................................................... 9 Sampling methods......................................................................................... 9 Statistical analysis ....................................................................................... 10 Results............................................................................................................ 10 Spider community composition.................................................................... 10 Microhabitat associations ............................................................................ 11 Prey availability ........................................................................................... 12 Discussion......................................................................................................