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Ground-Dwelling Beetles As Bioindicators in Transgenic Corn

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Ground-Dwelling Beetles As Bioindicators in Transgenic Corn ABSTRACT Title of Dissertation: GROUND-DWELLING BEETLES AS BIOINDICATORS IN TRANSGENIC CORN Miles David Lepping, Doctor of Philosophy, 2009 Directed By: Associate Professor Paula M. Shrewsbury, Department of Entomology & Professor Galen P. Dively, Department of Entomology Ecological risk assessment for transgenic crops requires identification of appropriate biological indicator organisms for use in laboratory and field biomonitoring studies. Ground-dwelling predatory beetles in the families Carabidae and Staphylinidae comprise a diverse and abundant group of nontarget organisms in field corn systems where rootworm-resistant transgenic varieties are deployed. First, the utility of two sampling methods (pitfall trapping and suction-based litter extraction) was assessed for estimating ground beetle (Coleoptera: Carabidae) population parameters in Maryland cornfields. Sampling bias was established for pitfall trapping, confirming the limitations of this semi-quantitative method for capturing a representative portion of the epigeal community. Litter extraction data conformed to predictions for abundance in relation to trophic identity, body size and biomass. Litter extraction identified smaller bodied carabid omnivores and carnivores as numerically dominant over larger bodied species that have received focus in risk assessment studies. A small-bodied carabid, Elaphropus xanthopus (Dejean), was identified as the dominant carnivore, and therefore selected for nontarget exposure and toxicity studies. Second, in choice and no-choice experiments, corn pollen was identified as a realistic, direct exposure pathway to transgenic proteins for E. xanthopus. Third, organism-level exposure to Cry34Ab1 rootworm-resistant protein was demonstrated for E. xanthopus in the laboratory and field during corn pollen shed. Field studies also revealed contamination across transgenic and non-transgenic test plots, indicating experimental design must account for the movement of study organisms and/or transgenic plant tissues. Finally, a toxicity study examined the effects of dietary exposure to rootworm-resistant Cry34/35Ab1 corn pollen for two beetle species, a carabid, E. xanthopus, and a staphylinid, Strigota ambigua (Erichson). Transgenic pollen exposure did not affect longevity or sub-lethal behaviors for either species. Small-bodied, predatory ground beetles are recommended as candidate bioindicator organisms in risk assessment studies designed to optimize field monitoring, exposure detection, and bioassay for transgenic pesticides. GROUND-DWELLING BEETLES AS BIOINDICATORS IN TRANSGENIC CORN By Miles David Lepping Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2009 Advisory Committee: Associate Professor Paula M. Shrewsbury, co-chair Professor Galen P. Dively, co-chair Professor Pedro Barbosa Associate Professor Bahram Momen Associate Professor Leslie Pick © Copyright by Miles David Lepping 2009 Acknowledgements The detail and complexity addressed by dissertation work is made possible by the enthusiasm of dedicated researchers who lend their time to develop emerging scientists. I am forever grateful to many for sharing their expertise and effort to bring this work to light. My matriculation into the Department of Entomology was facilitated by Bob Denno and Charlie Mitter. Two extraordinary researchers and mentors, Bob and Charlie jointly taught an introductory course that opened to me the world of entomology and its tremendous breadth and depth. By the end of that course, I knew my graduate training would focus on addressing questions in insect systems. The transformation that followed is reflected in every entomologist’s experience: voraciously seeking and consuming literature while pausing only to dash out into the field to capture and describe any and every taxa one can acquire. Upon netting my first libellulid during its optimal flight conditions, I knew I was hooked. Recognizing my passion, Charlie and Bob recommended me for a position in Paula Shrewsbury’s lab at the Smithsonian Institute. Shortly thereafter, Paula joined the faculty at Maryland and has since been my primary advisor and champion throughout my academic career. Her outstanding abilities as a mentor are evidenced by her students’ successes, and her dedication to my pursuits has been particularly selfless as my research broadened from the green industries into agriculture. Paula provided me the opportunity and autonomy to build a research program that merged ecology and microbiology, thus increasing my exposure to multiple disciplines and creating additional opportunities to train under an umbrella of expertise. At every turn, Paula has straightened the path. Her grace and good humor have accented her phenomenal mentoring and ameliorated the more challenging aspects of research. I have been one of the fortunate few to witness the establishment and growth of Shrewsbury Lab - a family whose bonds are as strong as our laughs are loud and long. Paula’s lab is a welcoming home and proving ground for our ideas, and will always be an environment I aim to recreate. An interest in nontarget organisms naturally led me to Galen Dively, who kindly accepted an invitation to join my committee and in short order generously offered me grant support and flexibility in selection of research trajectory. The community spirit in our department has been exemplified by the open door and busy hive of Dively Lab – the beacon of answers. Perhaps the only professor I’ve ever met whose desk is in the lab, Galen has made himself available to everyone, and provided or facilitated answers to just about every question. Galen’s ingenuity has reinvented the field of nontarget risk assessment. In this process he has shared his strategies and tools in a way that benefits everyone across the science and launches each of us closer to our goals. Galen has guided and inspired me to apply his methods to every facet of research. His affable and approachable personality has brought us all closer to a place where we share in his love of adventure. ii I thank Paula and Galen (AKA Palen) for their great friendship, guidance, and the chance of a lifetime. I look forward to the years to come. This work was considerably improved by my committee members and adjunct associates. I thank committee members Pedro Barbosa, Bahram Momen, and Leslie Pick for providing key suggestions and perusing these pages throughout the revision process. Thank you to Nicholas Storer and Guomin Shan at Dow AgroSciences, and Laura Higgins at Pioneer HiBred for project development and guidance. Thank you to fellow grant collaborators, Richard Hellmich, Jarrad Prasifka, and Leslie Lewis, USDA-ARS- CICGRU / Iowa State University for consulting and financial support. The insight and perspectives contributed by this group has increased the scope of these studies and facilitated their execution. I owe a debt of gratitude to a generous group of taxonomic experts, without which we would not have a common currency of communication in ecology. Thank you to Foster Purrington, The Ohio State University; Jan Klimaszewski, René Martineau Insectarium, Canadian Forest Service; Jennifer Beard, Ronald Ochoa, Matthew Buffington, and Andrew Carmichael, USDA-ARS-BARC; and Roy Norton, SUNY-ESF. Access to research facilities and materials is paramount. Thank you to Maryland farm owners and research farm managers that generously welcomed me into their fields and homes: Michael Cohey, Kevin Conover, Maxwell Covington Jr., Michael Dwyer, David Justice, Evan Miles, Donald Murphy, Daniel Schwaninger, and Peter Stifel. Thank you to fellow USDA researchers who facilitated field work in their backyard: Mathew Greenstone, Daniel Rowley, and Donald Weber, USDA-ARS-BARC; and who supplied research materials and expertise for laboratory investigations: Jonathan Lundgren and Chad Nielson, USDA-ARS-NGIRL. Thank you to University of Maryland researchers Judd Nelson, Leslie Pick, Michael Raupp, and Sandra Sardanelli for sharing their knowledge, humor, and access to their laboratory resources as if I was one of their own students. Thank you to our Information Technology administrators, Greg Hess and Alvin Wilson, for providing computer solutions to every challenge. Thank you to our Administrative and Business Staff members Tamma Hammond, Joanne Lewis, William Katsereles, and Jo Ann Smith, for supporting me in all endeavors and especially for their good natured humor over the years. Thank you to many undergraduate and high school student technicians and volunteers that successfully cut their research teeth in our ecology labs: Stephanie Buszczak, Heather Deckert, Oluseyi Emiola, Emily Hall, Zain Hasan, Michael Katsereles, Mario Khurran, Sam Minkove, Pragnesh Mistry, Matthew Moore, Amanda Nackos, Donna Pahl, Jonathan Pearson, Brittany Purnell, Samuel Ramsey, Clara Richards, Danteh Sema, Margaret Stevens, Erika Tucker, Andi Waghelstein, Jessica Watkins, Leslie Wells, Michael Wilson, and Stephanie Wyman. iii Thank you to fellow members in my home and sister laboratories for camaraderie and support throughout all seasons of research and life: William Ray Anderson, Peter Blank, Michael Embrey, Yong Lu, Terry Patton, Chris Sargent, Adrianna Szczepaniec, Cristel Thomas, and Hua Zhang. A special thank you is reserved for the lab managers and technicians who worked tirelessly to execute crucial steps and labored side-by-side with me in the trenches: Rut Finnsdóttir,
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