Eastern Illinois University The Keep Masters Theses Student Theses & Publications Fall 2020 Effects of insect opportunists on a four-level trophobiotic system involving nectar-producing galls of the cynipid wasp Disholcaspis quercusmamma (Hymenoptera: Cynipidae) Stephanie L. Smith Eastern Illinois University Follow this and additional works at: https://thekeep.eiu.edu/theses Part of the Entomology Commons, Evolution Commons, and the Other Ecology and Evolutionary Biology Commons Recommended Citation Smith, Stephanie L., "Effects of insect opportunists on a four-level trophobiotic system involving nectar- producing galls of the cynipid wasp Disholcaspis quercusmamma (Hymenoptera: Cynipidae)" (2020). Masters Theses. 4851. https://thekeep.eiu.edu/theses/4851 This Dissertation/Thesis is brought to you for free and open access by the Student Theses & Publications at The Keep. It has been accepted for inclusion in Masters Theses by an authorized administrator of The Keep. For more information, please contact [email protected]. Effects of insect opportunists on a four-level trophobiotic system involving nectar-producing galls of the cynipid wasp Disholcaspis quercusmamma (Hymenoptera: Cynipidae) Stephanie L. Smith A Thesis Submitted for the Requirements for a Degree of Master of Science Department of Biological Sciences, Eastern Illinois University Charleston, IL, USA Thesis Advisor: Dr. Zhiwei Liu Committee Members: Dr. Ann Fritz Dr. Scott Meiners Copyright 2020 by Stephanie L. Smith ABSTRACT The induction of plant galls is considered an adaptive life history trait found in many insect groups. The formation of galls provides several advantages to the gall maker, such as enhanced nutrition, favorable microclimate, and protection from natural enemies, including parasitoids, inquilines, and predators. Order Hymenoptera has many gall- making species, belonging to the gall wasp family Cynipidae. As an extended phenotype of the gall makers, some galls exhibit very sophisticated adaptive mechanisms involving multilevel species interactions. In particular, the oak galls of the Cynipid species Disholcaspis quercusmamma, found in much of Illinois, produce a palatable, sugary nectar-like secretion, attracting other insects. It is hypothesized that visiting insects discourage potential parasitoids and inquilines questing for oviposition sites within the galls, possibly producing an enemy-free space. Several studies on the species interactions involved in this four-level trophobiotic association have examined the role of visiting ant species in the system. However, other insect species have also been observed to be attracted to the extrafloral nectar of the galls, and their roles in the gall wasp-natural enemy interaction system have not yet been studied. This study aimed to examine the effects of all visiting insects, including ants, on the success of the gall-makers as a result of potentially reduced parasitism. Exclusion experiments were carried out on three oak trees in study sites in central Illinois. Statistical analyses of field data found no effect of treatment on gall wasp success, parasitism, or inquilinism. However, additional tests showed a positive correlation between gall wasp success and inquilinism rate compared to gall cluster size. Gall diameter correlated positively with gall maker success and i negatively with inquilinism rate. This suggests an underlying complexity to the system. Additional research is necessary to better understand this uniquely adapted relationship. ii ACKNOWLEDGEMENT First and foremost, I would like to extend my sincerest gratitude to my advisor, Dr. Zhiwei Liu. His great passion for gall wasps has inspired me and given me the perseverance to complete this thesis. Thank you for all the encouragement and kind words along the way. You have been the best advisor I could have ever hoped for! I would also like to extend thanks to my thesis committee, Dr. Ann Fritz and Dr. Scott Meiners. Dr. Fritz’s introductory entomology course was another source of inspiration for this project, and I will always deeply appreciate her advice, both entomological and personal. Dr. Meiners’ melodious mathematical musings further cemented my interest in all things statistical, and his help with the dataset for this project was incredibly valuable. I am also indebted to Dr. Britto Nathan, Dr. Gary Bulla, and Marschelle McCoy, who all had a part in making my time at Eastern Illinois University an enjoyable journey. Thank you all so much for indulging my interest of insects during my time at EIU, and for making me feel like a part of the family. Additionally, I extend a deep appreciation to Erin Shulk, who helped me with the experimental setup. She jumped headfirst into assisting me with this experiment and applied treatments to the tallest branches when my fear of heights got the best of me. Thank you so much, Erin! I appreciate the cooperation of the staff at Fox Ridge State Park. Without their permission and support, this experiment would never have taken place. Thank you for maintaining such a beautiful nature preserve. iii The obligatory ‘last but not least;’ my loving family. I will always be thankful for your support and interest in my project. Thank you so much for listening to my thought processes and providing such a wonderful sounding board, even when my ramblings made absolutely no sense. To my parents, who went with me to my first visit at EIU and provided unwavering support as soon as I knew that it was the program for me. To my grandparents, who allowed me to conduct part of my study on their property, and whose house always feels like home. To my aunt and godparents, who are happy to provide encouragement, a listening ear, or just a well-timed joke, even from afar. To my nephew, whose interest in insects I am always happy to indulge – for the best way to learn is to teach someone else. And to my husband, who would follow me to the ends of the earth to help support my dream. I love you all beyond measure. iv TABLE OF CONTENTS ABSTRACT ........................................................................................................................ i ACKNOWLEDGEMENT ............................................................................................... iii LIST OF FIGURES ......................................................................................................... vi LIST OF TABLES ......................................................................................................... viii INTRODUCTION............................................................................................................. 1 MATERIALS AND METHODS ................................................................................... 10 Study sites ...................................................................................................................... 10 Treatments ..................................................................................................................... 10 Observations.................................................................................................................. 11 Data collection .............................................................................................................. 11 Statistical analyses ........................................................................................................ 12 RESULTS ........................................................................................................................ 13 Observations.................................................................................................................. 13 Statistical analyses ........................................................................................................ 14 DISCUSSION .................................................................................................................. 16 REFERENCES ................................................................................................................ 20 v LIST OF FIGURES Figure 1. The nectar-producing galls of Disholcaspis quercusmamma……………...….26 Figure 2. An inquiline of Disholcaspis quercusmamma……………...……………...….27 Figure 3. Map of study sites in Central and East Central Illinois……………..………...28 Figure 4. Mesh bags made of ½” mesh garden netting.……………………..…………..29 Figure 5. Fruit bags secured around the galled portion of the branches……...…………30 Figure 6. A Disholcaspis quercusmamma gall cut open to reveal the central gall chamber in which the larva resides…………….………...…………………………………….…..31 Figure 7. A carpenter ant (Camponotus sp.) visiting the nectar-producing galls…….....32 Figure 8. A northern paper wasp (Polistes fuscatus) visiting the nectar-producing galls Courtesy Zhiwei Liu………………..……………………………………………..……..33 Figure 9. A cuckoo wasp (Chrysis sp.) and housefly (family Muscidae) visiting the nectar-producing galls. Courtesy Zhiwei Liu……………………………………………34 Figure 10. A great black wasp (Sphex pensylvanicus) visiting the nectar-producing galls. Courtesy Zhiwei Liu………………………………………………………..…………....35 Figure 11. An Asian lady beetle (Harmonia axyridis) and several houseflies (family Muscidae) visiting the nectar-producing galls. Courtesy Zhiwei Liu.……………...……36 Figure 12. A wheel bug (Arilus cristatus) visiting the nectar-producing galls……...……………………………………………………………………………….37 Figure 13. Red-spotted purple butterflies (Limenitis arthemis) visiting the nectar- producing galls. Courtesy Zhiwei Liu.………...…………………………………….…..38 Figure 14. Black sooty mold on