Winter-Emerging Chironomidae (Insecta: Diptera) in Minnesota Trout Streams A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Alyssa Mae Anderson IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Leonard C. Ferrington, Jr., Advisor December, 2012 © Alyssa Mae Anderson, 2012 Acknowledgements I could not have completed this work without the help and support of many individuals. First and foremost, I wish to thank my advisor, Dr. Len Ferrington, for all of the guidance, discussion, support, and encouragement he has offered over the past five years, and, of course, for sharing and passing on his passion and fascination with Chironomidae research. Len has helped to both focus and broaden my interests in aquatic entomology, conservation biology, and science as a whole. Additionally, Len has provided strong support and encouragement for my pursuit of numerous opportunities throughout the course of my graduate career, including research grants and fellowships, teaching and presentation opportunities, and international research and scholarship activities, all of which have greatly contributed to and enhanced my scholarly and professional development. Secondly, many thanks also go to Dr. Torbjørn Ekrem and Dr. Elisabeth Stur, at the Norwegian University of Science and Technology (NTNU) Vitenskapsmuseet (Museum of Natural History and Archeology), for inviting me to spend a year working and learning from them while on a Fulbright Scholarship in Trondheim, Norway. Torbjørn and Lisa’s enthusiasm for their work was infectious, and their patience and skill for teaching new techniques has helped me to shape my own abilities and ideals as a teacher and research advisor. Furthermore, they helped me to develop a true passion for an area of research that I would not have otherwise pursued. I am also very grateful for their hospitality and friendship, which immediately made me feel welcome in a new country and work environment. Thanks also to my graduate committee, Ralph Holzenthal, Roger Moon, and Bruce Vondracek, for assisting with i study design and for asking critical questions and providing comments that helped me to define my research questions and think more critically about my research objectives. I must also extend my gratitude to my many colleagues and friends at both the University of Minnesota and the NTNU Vitenskapsmuseet who provided me with valuable insights, good advice, he fu criti ues, stron encoura ement, and reat discussions. ecifica y, must thank ast and resent members of the ni ersity of innesota’s hironomidae esearch rou , es ecia y i ouchard, etra ran fe der, rian cheut , sabet annesd ttir, Jessica Miller, Will French, Alex Egan, Clair Bleser, Jane Louwsma, and Lori Krider. Special thanks also go out to friends from my time at the Vitenskapsmuseet Section of Natural History, particuarly Sondre Dahl, Susan Gresens, Fabio Laurindo da Silva, and Magni Olsen Kyrkjeeide. Thanks also to fellow UMN-Trondheim Fulbrighters Meghan Jacobson, Rolf Jacobson, and Andrew Carlson for their friendship and support both home and abroad. Thanks to the long list of individuals (Joel Anderson, Shirley Anderson, Blair Bollig, Chris Chizinski, Allison Cranston, Erin Dahlke, Amber Eule-Nashoba, David Huff, James Jarvis, Carol Jefferson, Petra Kranzfelder, Jessica Miller, Loren Miller, Dave Montgomery, Kyle Narveson, John Roberts, Nathan Roberts, Bruce Vondracek, and Winnie Winikoff) who spent long and often sub-zero days in the field with me, particularly David Huff, who helped define field methodology for the second chapter of my dissertation, and Joel Anderson, who helped out with all of the field work associated with the second chapter. Also, thanks to numerous undergraduate students who helped sort through and identify samples in the laboratory, especially Erin Mittag and Bridget ii Peterson, who also helped to develop and conceptualize many important ideas, concepts, and discussion points in Chapter 2. This work could not have been accomplished without financial support from the following sources: a College of Food, Agriculture, and Natural Resource Sciences Global and Environmental Change Graduate Fellowship; a Department of Entomology Sping and Ying-ngoh T. Lin Graduate Fellowship; a Fulbright Grant from the U.S.-Norway Fulbright Foundation and the University of Minnesota Graduate School/Norwegian University of Science and Technology Fulbright Scholarship Exchange Program; a P.E.O. Scholar Award from the International Chapter of the P.E.O. Sisterhood; two Torske Klubben Graduate Fellowships; a Norwegian Marshall Fund Award from the Norway-America Association; a Morris and Elaine Soffer Rockstein & Graduate School Fellowship; a University of Minnesota Graduate School Summer Block Fellowship; several Dayton Bell Museum Fund Research Fellowships; a University of Minnesota Thesis Research Grant, and several Entomology - Graduate School Block Grant Travel Fellowships. I also thank Jim Sublette, Peter Langton, Trond Andersen, Martin Spies, Claus Lindegaard, Anker Halvorsen, and Will Bouchard for arranging loans or donations of material that aided with the research presented in Chapter 3. Finally, I could not have come this far without the support and encouragement of my friends and family, who always help to put things in perspective and keep life balanced. I am especially grateful for the support and love of my parents, Shirley and Joel Anderson, who always have encoura ed me to ‘shoot for the stars.’ f they hadn’t tromped around streams with me and let me turn their kitchen into a make-shift iii aboratory for days at a time when was in hi h schoo , certain y wou dn’t be where am today! Another big thanks to my Dad, and fishing buddy (both traditional rod-and- reel and the more hi-tech back-pack electroshocking), for spending numerous cold winter days wading through streams with me in search of trout that we would then have to spend hours processing in a stream-side fish house. Thanks always to Nathan Roberts, for his companionship, for always helping me to keep a smile on my face, for understanding all of the long hours spent at the computer, in the lab, and overseas, and of course for always being a ready and willing volunteer. Thanks also to my uncle, Al Flieder, for the use of ‘As en Lake etreat enter and F eet er ices’ durin the arduous rocess of dissertation writing. Finally, thanks to my Grandparents, Emil and Hazel Flieder, for their love and encouragement as well as the generous funds they provided that helped to support me throughout my pursuit of higher education. iv Dedication This dissertation is dedicated to the memory of my Grandma, Hazel Flieder. For always encouraging me to work hard to pursue my dreams; But more importantly, to take the time to slow down and enjoy life and the people that make it meaningful. v Abstract The Chironomidae (Diptera) is among the few aquatic insect families with species that are reliably able to grow, develop, and emerge as fully functional adults throughout the cold winter months that characterize the midwestern United States. However, few studies document their role in trout streams during this time of year. The intent of this dissertation is to enhance the field of Chironomidae research by focusing on the winter dynamics of these insects, including their response to severe flood events, their incorporation in the winter diet of trout, and the morphological and molecular description of three new cold-adapted Chironomidae species. The resistance and resilience of the winter chironomid community was assessed following a severe flood that impacted many streams in southeast Minnesota during the late summer of 2007. Methodology included collections of chironomid surface-floating pupal exuviae from 18 southeast Minnesota streams; streams were selected to include representation of localities that incurred moderate to extreme levels of flooding disturbance. These data were compared to data from the same localities during prior winters. Significantly more taxa emerged during the winter after late-summer flooding as compared to historic collections, and the number of species emerging in winter was positively correlated with rainfall severity, indicating the winter-active Chironomidae are resistant to late summer spates. This indicates that chironomids are an available winter food resource to stream trout recovering from devastating floods. In attempt to examine the importance of Chironomidae and other winter-active aquatic insects to the winter diet of brown trout (Salmo trutta L.), stomach contents were collected from trout inhabiting three southeast Minnesota streams; these vi data were compared to organisms collected in the stream drift and benthos. Results indicated that trout diets differ by stream and by fish size, with larger trout feeding heavily on Trichoptera and Physella, and smaller fish relying more on Gammarus and Chironomidae larvae. Stomach contents were more similar to the benthos than the drift, indicating a greater reliance on benthic feeding during winter. Trout in all streams selected Trichoptera and Chironomidae over other prey, and appeared to maintain size- selective predation throughout winter. Winter-emerging Chironomidae appear to enhance the trout diet in all streams, and chironomid larvae were particularly dominant in the diet of one trout population. Three new chironomid species within the genus Micropsectra, a genus commonly found in the winter trout diet, were discovered from a study of five