IMPACTS OF A SEED PREDATOR ON SUNDIAL LUPINE Jennifer Shimola A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2013 Committee: Dr. Helen Michaels, Advisor Dr. Randy Mitchell Dr. Daniel Pavuk Dr. Daniel Wiegmann © 2013 Jennifer Shimola All Rights Reserved iii ABSTRACT Helen Michaels, Advisor Sundial lupine, Lupinus perennis (L.), is a perennial flowering legume integral to maintaining reproductive populations of the federally endangered Karner Blue butterfly. The seed coats of L. perennis are polymorphic, with variable amounts of dark speckling ranging from light to heavily speckled against a white to gray background. In this legume species, darker seeds may contain secondary metabolites like tannins and anthocyanins, which may be associated with deterring seed predation. Other studies have found lighter colored seeds to have weaker seed coats, be more digestible, and have higher nutritional value than darker seeds. The chemical and physical traits of lighter seed coats could make this seed type more desirable for seed predators as well as agriculturalists. The seeds of L. perennis are a known food source of ant-mimicking alydid insects, Megalotomus quinquespinosus and Alydus spp. This study explored whether alydids have a preference for seed coat color variants of L. perennis and simultaneously determined the relative abundance of this seed predator and the frequency of L. perennis seed colors in field surveys of ten populations. We expected to find that 1) alydids would be found at greater frequencies when lighter seeds were present and 2) the most amount of time during a seed choice experiment will be spent interacting with lighter seeds. We also measured environmental characteristics to determine whether other factors may be playing a role in the distribution of L. perennis seed color or alydids. We expected soil characteristics to camouflage seeds, canopy cover and litter depth would influence site productivity, and that greater food availability would increase alydid abundance. iv Populations of L. perennis were surveyed for seed color frequencies, alydid frequencies, environmental variables, and the presence of other legume species. Sites were confirmed to differ in the amount of speckling and proportion of seeds with speckling present. Seed speckling was impacted by soil characteristics, canopy cover, and pod abundance. Alydid abundance was impacted by food availability (pod abundance and the presence of other legumes), soil characteristics, and the amount of speckling. Fewer alydids were found in populations with darker speckled seeds. A multiple choice behavioral experiment was performed on adult M. quinquespinosus to clarify findings of the population survey. There was no significant difference in alydid behavior with different seed colors, though we observed a trend of greater time interacting, a greater proportion of time, and more frequent visits to darker seeds. Based on the findings of our population survey and behavioral experiment, alydids did not have a strong preference for lighter seed colors in L. perennis. Some explanations for the differences in seed color abundance among sites are that seed color is random or undergoing selective pressures that we did not consider such as post-dispersal seed predators, the attraction of beneficial microbes, maintaining non-synchronous germination, or pleiotropic effects. Understanding whether this seed color polymorphism is important to L. perennis fitness may be important in future management decisions and should be further studied. v ACKNOWLEDGMENTS First and foremost, I wish to acknowledge Dr. Helen Michaels, as she has helped me find a project to be enthusiastic about, helped me develop the skills to improve myself in the field of ecology, and inspired me to pursue this research further. I would also like to thank my committee, Dr. Randy Mitchell, Dr. Daniel Pavuk, and Dr. Daniel Wiegmann, for their helpful input in designing this project. Thank you to Nancy Boudreau and various graduate students in the statistical consulting office of Bowling Green State University’s Business Administrative department who helped difficult data become analyzable. Furthermore, I would like to thank my lab mates (Mike Plenzler, Ryan Walsh, Jacob Meier, Jacob Sublett, Paige Arnold, and Alyssa Dietz) for keeping the lab fun, answering endless inquiries, and helping me become both a better presenter and writer through many tedious lab meetings. A big thanks to the CURS program at BGSU for funding this project and giving me the opportunity to mentor an undergraduate field assistant, Jacob Sublett, whose hard work and enthusiasm for field and lab work is greatly appreciated Finally, I would like to thank the management agencies that permitted us access to our lupin populations: The Metroparks of the Toledo Area, Ohio Department of Natural Resources, Division of Wildlife, and The Nature Conservancy. vi TABLE OF CONTENTS Page INTRODUCTION ................................................................................................................. 1 METHODS....................... ..................................................................................................... 6 Study Species and Study Area....................... ............................................................ 6 Population Survey....................... ............................................................................... 8 Behavioral Experiment....................... ....................................................................... 9 Statistical Analysis....................... .............................................................................. 10 RESULTS.......................... .................................................................................................... 13 Population Survey....................... ............................................................................... 13 Population Means Analysis........................................................................................ 16 Behavioral Experiment....................... ....................................................................... 17 DISCUSSION........................................................................................................................ 19 REFERENCES....................................................................................................................... 25 TABLES AND FIGURES....................................................................................................... 35 APPENDIX A. Correlation of Variables .............................................................................. 66 APPENDIX B. Parameter Estimates .................................................................................... 67 vii LIST OF TABLES Table Page 1 GPS coordinates and managing agencies of populations surveyed ........................... 35 2 Percent of samples with white or speckled seeds by site ........................................... 36 3 Population means for environmental variables .......................................................... 37 4 The relationship of site, alydid abundance, soil value, and the presence of two other legumes on the amount of seed speckling.................................................................. 38 5 The relationship of environmental factors and seed characteristics on the presence of seed speckling and alydid abundance ................................................................................ 39 6 Models of speckling and alydid abundance .............................................................. 40 7 The time spent with seeds and proportion of time spent with seeds by seed color ... 41 8 Relationship of first visit and frequency of visits to seed color ................................. 42 viii LIST OF FIGURES Figure Page 1 Distribution of amount of speckling by site ............................................................... 43 2 Relationship between site and amount of speckling .................................................. 44 3 Relationship of soil value and amount of speckling .................................................. 45 4 Relationship of the presence of two other legumes and the amount of speckling ..... 46 5 Relationship of site and the presence of speckling ................................................... 47 6 Relationship of soil chroma and presence or absence of speckling ........................... 48 7 Relationship of pod density and the proportion of seeds with speckling present ...... 49 8 Relationship of Lespedeza capitata presence and the proportion of seeds with speckling present......................................................................................................................... 50 9 Relationship of site and alydid abundance when considering the degree of speckling 51 10 Relationship of soil value and alydid abundance when considering the degree of speckling..................................................................................................................... 52 11 Relationship of canopy cover and alydid abundance when considering the degree of speckling..................................................................................................................... 53 12 Relationship of average amount of speckling and alydid abundance when considering the degree of speckling..............................................................................................