The Effects of Warming on Aquatic Insects – Individual to Community Responses by Dachin N. Frances A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Ecology and Evolutionary Biology University of Toronto © Copyright by Dachin N. Frances 2018 The Effects of Warming on Aquatic Insects – Individual to Community Responses Dachin N. Frances Doctor of Philosophy Department of Ecology and Evolutionary Biology University of Toronto 2018 Abstract Climate change is increasing temperatures globally as well as the frequency and severity of extreme events such as heat waves. Given that the majority of animals on Earth are ectothermic, and therefore physiologically linked to environmental temperatures, it is imperative to predict the impacts of future warming on species. The physiological effects of warming on ectotherms have been studied extensively, yet, species interactions can also be affected by temperature. My thesis assessed how differences in species’ responses to warming affect their interactions and ultimately the structure and dynamics of communities. I first asked if phenological and early developmental responses to warming differed among and within dragonfly species. Warming accelerated growth and developmental rates, however, differences were greater within as opposed to between species in these responses. I also examined whether differences in behavioural responses to warming among species could determine which species became the superior IG predator. Foraging and IGP rates increased with warming but activity level changes were not predictive of the outcome of these interactions. Next, I asked how the interactive effects of warming and predator presence affected prey foraging decisions. Warmer conditions appeared to have a greater impact on prey behaviour that the predator presence, even though the prey’s risk of being eaten increased with temperature. Lastly, I manipulated developmental conditions in pond mesocosms to understand how warming and heat waves affect community structure. ii Heat waves similarly increased species’ evenness in communities as warming. However, heat waves further boosted survival compared to ambient and warmed conditions, strengthening consumption on primary consumers within these food webs. Together, my thesis demonstrates the importance of understanding complex interactions between species to make more accurate predictions of the effects of future warming on communities. iii Acknowledgments First and foremost, I would like to thank my supervisor, Shannon McCauley. Her enthusiasm and passion for her work is contagious, which is what initially drew me in at the start of my PhD. Since then, her constant support and endless wisdom have been pivotal in guiding me along this academic journey. In addition, she and Steph Schneider have provided hours of conversation, humor, stories, and advice. Thank you both for your generosity, kindness, and van-shuttling! I also owe Karen Mabry a huge thank you, as she is the one who introduced me to Shannon in the first place. Thanks Karen, for hiring me as a technician my first summer after undergrad and being a great collaborator in the years following. In addition, I would like to generally thank the University of Toronto’s Department of Ecology and Evolutionary Biology for funding me all these years, the Department of Biology at the University of Toronto Mississauga for generous conference funding and support for BGSS, the office of the Vice Dean Graduate for their generous funding to graduate students, all the graduate students involved in UTMAGS who worked hard to improve graduate student life, and the American Museum of Natural History, the Animal Behavior Society for funding part of my research and trips to conferences. More specifically, I would like to thank members of my doctoral committee: Doug Currie, Benjamin Gilbert, and Marc Johnson for their feedback and advice on my PhD research. Also, thank you, Marc, for reading and commenting on my thesis while traversing the globe on sabbatical. Thanks also to Sanja Hinić-Frlog, for being a great mentor and teaching me so much about pedagogy and birds! I would also like to thank Helen Rodd for her tireless and sincere commitment to graduate students in EEB. Thank you to Darryl Gwynne for being on my appraisal committee and generally just being an interesting person to talk to. Also, thank you, Mary O’Connor, for being on my defense committee and asking thorough and excellent questions that made me think broadly about my work and how it intersects with the field. I also thank members of the McCauley lab: Sarah French, Celina Baines, Rosemary Martin, Ilia Ferzoco, Ros Murray, Chris Searcy, Shantel Catania, Tharusha Wijewardena, Tammy Duong, Jy Moon, David Przelicki, Sam Hasbum, and Rosalynn Mitchell. I feel so fortunate to be part of such a supportive, creative, and brilliant group. Thanks also to every ROP/intern/work iv study/thesis undergraduate student that put in hours of field and lab work – this thesis would have taken years longer if not for you! Next, I thank the graduate students in the department whom I have grown close with over the past few years: Audrey Reid, Laura Junker, Kyla Ercit, Michelle DiLeo, Becci Rooke, Mark McDougall, Aaron LeBlanc, Krystal Nunes, Amy Wong, Nash Turley, Yara Haridy, Lauren Barth, Ernest Prack, Ruth Rivkin, Molly Hetherington-Rauth, Diego Carmona, James Santangelo, Jessica Brown, Cylita Guy, Arjan Banerjee, Kayla Dias, Alex Paquette, Mireille Golemiec, Chris Wong, Jade Atallah, Andrew Catalano, and many more. Thank you all for making my experience here an amusing and unique time! Lastly, I’d like to thank my family. Thank you all for your constant support and unconditional love. Living in a different country than you was challenging at times, but I always looked forward to seeing you all once or twice a year and I cherish all of those memories. Of course, I can’t end the acknowledgements section without thanking my husband. Thank you, Connor, for being my foundation, my sentinel, and my number one, unwavering supporter. I am so thankful that we could do this journey together and I’m looking forward to embarking on our future path together after this chapter in our lives. v Table of Contents Acknowledgments ..................................................................................................................... iv Table of Contents ...................................................................................................................... vi List of Tables ............................................................................................................................... x List of Figures............................................................................................................................. xi List of Appendices ................................................................................................................... xiii General Introduction ..................................................................................................1 1 Introduction ........................................................................................................................1 1.1 Present and future climate change...............................................................................1 1.1.1 Species responses to climate change ...................................................................2 1.1.2 Phenological shifts ...............................................................................................3 1.1.3 Range shifts .........................................................................................................3 1.1.4 Shifts in body size – The temperature-size rule ....................................................4 1.2 Study system ................................................................................................................5 1.2.1 Odonate responses to climate change .................................................................6 1.2.2 Odonates as structuring agents of communities ..................................................8 1.3 Thesis overview ..........................................................................................................11 1.3.1 Chapter 2 ...........................................................................................................11 1.3.2 Chapter 3 ...........................................................................................................12 1.3.3 Chapter 4 ...........................................................................................................12 1.3.4 Chapter 5 ...........................................................................................................13 1.4 References .................................................................................................................13 Effects of warming on early life history ...................................................................19 2 Abstract ............................................................................................................................19 vi 2.1 Introduction ...............................................................................................................19 2.2 Materials and methods ..............................................................................................23 2.2.1 Study system ......................................................................................................23