Testing the effects of glyphosate and a possible tradeoff with immunity on native and non-native species of crickets Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Lydia Rose Mullins Graduate Program in Evolution, Ecology and Organismal Biology The Ohio State University 2020 Thesis Committee Dr. Susan Gershman, Advisor Dr. Ian Hamilton Dr. Roman Lanno 1 Copyrighted by Lydia Rose Mullins 2020 2 Abstract Introduced insects can compete with native species and alter population and community dynamics. To minimize these effects and potential threats to biodiversity, it is necessary to understand the mechanisms that lie behind successful colonization of novel environments by introduced species, including anthropogenic factors such as herbicides. Glyphosate, the active ingredient of Roundup, is a broad-spectrum herbicide that is commonly applied to various types of land across the world. Its application increased dramatically after the introduction of glyphosate-resistant crops, leading glyphosate to become the top-selling herbicide worldwide. Although it is so widely used, its effects on wildlife are extremely under-studied. Of the few studies examining glyphosate’s effects on non-target organisms, it has been shown to affect locomotion, reproduction, memory and learning of various species of arthropods. It is necessary to understand how glyphosate may be impacting invasion success of non-native insects. The present study examines these effects on native and non-native species of crickets. Further, competition with invasive species and exposure to herbicides may reveal or emphasize existing tradeoffs between traits. For example, many crickets trade off effort devoted to reproduction and immunity. Crickets commonly face immune challenges in the wild, so it is possible that a trade-off may lie in managing exposure to agrochemicals like herbicides and investment into immune function. If present, this trade-off may be contributing to the ii success of non-native species competing with native species and colonizing novel environments. Therefore, in the present study, I examine the effects of glyphosate and a possible trade-off with immunity on lifespan, calling effort and fecundity in the native fall field cricket, Gryllus pennsylvanicus and the non-native Japanese burrowing cricket Velarifictorus micado. G. pennsylvanicus and V. micado occupy a similar niche and therefore are expected to be in competition with each other for resources. V. micado has also been observed in higher abundance than G. pennsylvanicus in the field, suggesting higher success in competition for resources. In this study, we found that glyphosate decreases survival of juvenile Gryllus vocalis and has no effect on adult lifespan of Gryllus pennsylvanicus or Velarifictorus micado. Both G. pennsylvanicus and V. micado females produce more eggs when sprayed with glyphosate. G. pennsylvanicus females also show an interaction between glyphosate and immune challenge; those sprayed with glyphosate and provided with an induced immune challenge produce fewer eggs than females sprayed with glyphosate that are not immune challenged. Because this interaction is not present in V. micado females, this could potentially explain the successful establishment of V. micado. Glyphosate does not affect male calling effort of either G. pennsylvanicus or V. micado. These results suggest that glyphosate may impact survival and reproduction of non-target organisms and has varying effects based on species and may contribute to colonization by non-native species. The survival effect that we observed may be due to additional ingredients in commercial formulations of glyphosate such as surfactants, rather than pure glyphosate. In order to minimize the potential contribution of glyphosate to colonization of novel habitats by non-native species, further iii studies are needed to better understand the potential consequences of this extensively used herbicide and to disentangle whether these effects are actually caused by glyphosate or other ingredients commonly found in Roundup. iv Dedicated to my Papaw, my Mamaw, and my Poppy – You are so missed v Acknowledgments I would like to thank my advisor, Susan Gershman, for her continued support and guidance. Without her assistance, this work would not have been possible. I would also like to thank the other members of my committee, Ian Hamilton and Roman Lanno, for their valuable help throughout this process. This work would also not have been completed without the help of Salvatore Sidoti, Bridget Brown, Jaret Cingel, Leigh Carrabia, Erin Schuster, Marisa Nicol, Malek Soumakieh, Nihit Tyagi and Haley Ries. To my parents, my brother and my grandma Carolyn – I would be lost without your unwavering love and support. Thank you to the faculty and my fellow graduate students in EEOB for being so welcoming and encouraging. To my friends Jimmy Chiucchi, Chloe Flanigan, Drew Spacht, and Kunal Chatterjee – thank you for your endless support and helping me grow as a teacher, a graduate student, and most of all as a person along the way. vi Vita May 2018…………………………………………………………………….B.S. Biology, The Ohio State University 2018-2020………………...…………….…………………..Graduate Teaching Associate, The Ohio State University Fields of Study Major Field: Evolution, Ecology and Organismal Biology vii Table of Contents Abstract ............................................................................................................................... ii Dedication ........................................................................................................................... v Acknowledgments .............................................................................................................. vi Vita .................................................................................................................................... vii List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x Introduction ......................................................................................................................... 1 Materials and Methods ........................................................................................................ 8 Results ............................................................................................................................... 16 Discussion ......................................................................................................................... 20 Conclusions ....................................................................................................................... 26 Bibliography ..................................................................................................................... 40 viii List of Tables Table 1. Summary of studies examining the effects of glyphosate on non-target terrestrial arthropods ......................................................................................................................... 28 ix List of Figures Figure 1. Recruitment of crickets for treatments .............................................................. 29 Figure 2. Effect of glyphosate on juvenile G. vocalis survival ......................................... 30 Figure 3. Effect of glyphosate on water consumption ...................................................... 31 Figure 4. Effect of glyphosate on food consumption ........................................................ 32 Figure 5. Effect of spray and injection on G. pennsylvanicus fecundity .......................... 33 Figure 6. Effect of spray and injection on V. micado fecundity ....................................... 34 Figure 7. Effect of species on fecundity ........................................................................... 35 Figure 8. Effect of species on adult lifespan ..................................................................... 36 Figure 9. Effect of spray and injection on lifespan of G. pennsylvanicus adults .............. 37 Figure 10. Effect of spray and injection on lifespan of V. micado adults ......................... 38 Figure 11. Effect of species, injection and spray on calling effort ................................... 39 x Introduction Introduced insect species are highly successful at becoming established in novel environments (Brockerhoff and Liebhold 2017). They play influential roles in ecosystems, including various roles in food web interactions and contributions to numerous ecosystem processes such as nutrient cycling and pollination. Therefore, they may have drastic impacts on recipient habitats, including altering community dynamics and threatening biodiversity (Brockerhoff and Liebhold 2017; Fahrner and Aukema 2018). To become established, invasive species must compete with native species that occupy similar niches. This could potentially lead to niche displacement or competitive exclusion of native species (Mooney and Cleland 2001). Considering the various impacts non-native insects may have on natural systems, it is necessary to understand the mechanisms that lie behind their successful establishment. In addition to competition with introduced species, insects face other challenges in the wild such as immune challenges and negative effects