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Western University Scholarship@Western Electronic Thesis and Dissertation Repository 12-1-2011 12:00 AM Overwintering energetics of Lepidoptera: the effects of winter warming and thermal variability. Caroline M. Williams University of Western Ontario Supervisor Dr. Brent Sinclair The University of Western Ontario Graduate Program in Biology A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Caroline M. Williams 2011 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Comparative and Evolutionary Physiology Commons Recommended Citation Williams, Caroline M., "Overwintering energetics of Lepidoptera: the effects of winter warming and thermal variability." (2011). Electronic Thesis and Dissertation Repository. 323. https://ir.lib.uwo.ca/etd/323 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. OVERWINTERING ENERGETICS OF LEPIDOPTERA: THE EFFECTS OF WINTER WARMING AND THERMAL VARIABILITY (Spine title: Overwintering energetics of Lepidoptera) (Thesis format: Integrated Article) by Caroline Margaret Williams Graduate Program in Biology A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy The School of Graduate and Postdoctoral Studies The University of Western Ontario London, Ontario, Canada © Caroline Williams, 2011 THE UNIVERSITY OF WESTERN ONTARIO School of Graduate and Postdoctoral Studies CERTIFICATE OF EXAMINATION Supervisor Examiners ______________________________ ______________________________ Dr. Brent Sinclair Dr. Michael Angilletta Supervisory Committee ______________________________ Dr. John Millar ______________________________ Dr. Louise Milligan ______________________________ Dr. Louise Milligan ______________________________ Dr. James Staples ______________________________ Dr. Liz Webb The thesis by Caroline Margaret Williams entitled: Overwintering energetics of Lepidoptera: the effects of winter warming and thermal variability. is accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy ______________________ _______________________________ Date Chair of the Thesis Examination Board ii Abstract and Keywords Winter temperatures are changing rapidly, and although winter warming reduces cold stress for overwintering ectotherms, temperature-mediated increases in metabolic rate can decrease fitness in dormant insects by increasing consumption of energy reserves. Increases in thermal variability also increase energetic demands, due to non-linear thermal response curves. My objective was to quantify the negative effects of winter warming and increases in thermal variability on a range of Lepidopteran species. As overwintering insects rely on lipid catabolism, accurate lipid measurement is central to my dissertation; so I first compared four methods of lipid quantification; concluding thin layer chromatography was the only method sufficiently accurate and robust to variation in lipid composition. I then examined the physiological and life-history costs of winter warming in Erynnis propertius [EP], Papilio glaucus [PG], P. troilus [PT], and Hyphantria cunea [HC]. A simple increase in temperature caused lipid depletion in EP, but PT, PG and HC were insensitive to winter warming. In HC, this insensitivity was mediated by a plastic suppression of metabolism and a decrease in development time in the warmer winter. HC from their northern range edge had increased thermal sensitivity at the end of winter, as predicted by metabolic cold adaptation theory. In EP, I also investigated the impact of daily thermal variability on overwintering energetics, demonstrating a facultative and obligate suppression of thermal sensitivity in response to high daily thermal variability, which partially compensated for the increased energetic demands of the more variable environment. Modelling energy use with meteorological data demonstrated that phenology changes had disproportionate influence on energetics in variable environments; thus timing of entry into winter dormancy will strongly influence ectotherm fitness in temperate environments. Metabolic suppression in EP and HC are the first demonstrations of metabolic compensation in overwintering insects. Finally, I outline a framework to predict insect vulnerability to winter warming. Winter warming and increases in thermal variability may negatively impact the fitness of some overwintering insects, but diverse physiological mechanisms compensate for increased energetic demands over winter. iii Keywords: Temperature, energy, triacylglyceride, lipid, insect, phenotypic plasticity, local adaptation, thermal sensitivity, metabolic compensation, metabolic cold adaptation, development time, phenology. iv Co-Authorship Statement Chapter 1 will form part of a review on the effects of climate change on overwintering insects, with Brent J. Sinclair (BJS), who contributed to the conception of many of the ideas and provided editorial comments on the writing. Chapter 2 was published in similar form in the Journal of Insect Physiology (reprint permission in Appendix 1). I was the first author, with co-authors Raymond H. Thomas (RHT), Heath A. MacMillan (HAM), Katie E. Marshall (KEM) and BJS. RHT provided expert technical assistance with the TLC-FID; KEM provided advice on the laboratory assays and statistical analyses; HAM provided advice on the laboratory assays and helped prepare the figures, BJS provided advice on the laboratory assays, contributed to experimental design, and helped write the manuscript. Chapter 3 is currently under review at Climate Research with Jessica J. Hellmann (JJH) and BJS, who had creative input into the conception of the work, contributed to developing the experimental design, and helped write the manuscript. Chapter 4 is currently in preparation for submission to Functional Ecology, with Wesley D. Chick, who collected and cared for the insects, and BJS, who contributed to the conception of the study, experimental design and choice of methods, gave advice on data analysis, and helped write the manuscript. Chapter 5 is under review in similar form at PLoS ONE, with myself as the first author and KEM, HAM, Jason D.K. Dzurisin (JDKD), JJH, and BJS as co-authors. KEM, JJH and BJS contributed to experimental design; HAM, KEM, JDKD and BJS helped perform the experiments; KEM performed the non-linear modeling of metabolic rate - temperature relationships, KEM, JDKD and HAM helped prepare the figures; KEM, JJH and BJS helped write the manuscript. Chapter 6 will (with Chapter 1) form part of a review on the effects of climate change on overwintering insects, with BJS, who contributed to the conception of many of the ideas and provided editorial comments on the writing. v Acknowledgments First of all, thank you to my mother, Jill Proudfoot, for unwavering love and support, and for encouraging me to pursue the opportunities that the world has presented. Thank you also to my sister, Belinda Williams, for support, companionship, and being a great Aunty. After my mother, no one has influenced my life more than my supervisor, Brent Sinclair. When I was a young undergraduate student, Brent, then a doctoral student himself, supervised my third year project. He encouraged me to pursue a Master’s degree, which he then co-supervised from abroad, and some years later he again showed confidence in me by inviting me to join his lab to do my PhD. Since then, he has been an exemplary mentor, providing a stimulating and challenging academic environment that has pushed me to fulfill the potential he recognised many years ago. Since Liana was born, his understanding and support have made it possible for me to continue to meet my suddenly- multifaceted responsibilities. Thank you Brent, for your rigorous and conscientious supervision, and for your friendship. For Chris Guglielmo and Yolanda Morbey; words are inadequate to express my gratitude for taking Liana and I into your home and supporting me through my first year of combining motherhood and PhD. You have both provided not only personal support but also contributed to my academic development, generously giving advice on all manner of issues; personal, career, statistical, biochemical, and theoretical. Thank you also to Linus and Nora for friendship and tolerance of the vagaries of babies. A special thank you to my advisory committee, Jim Staples and Louise Milligan, for their advice, guidance and friendship, and to Jim for reading my thesis so carefully pre- submission. It improved a lot as a result of your perceptive and no-nonsense comments. Many thanks to John Steele, who has been a patient mentor, and has taught me a lot about insect biochemistry. I also want to express thanks for the mentorship and opportunities provided to me by Jessica Hellman, who has developed the West Coast study system and has been generous with encouragement, advice and critical comments on manuscripts. Thank you to Matthias Lorenz and David Gray for helpful advice and discussion on lipid vi measurement, and diapause termination, respectively. Thank you to Mhairi McFarlane, Peter Carson, Mary Gartshore, and Andrea Schiller for facilitating my access to field sites, and Willem Roosenburg for maintaining the Ohio iButtons. John Lighton and Barbara Joos provided patient and knowledgeable

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