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Demography and Molecular Ecology of the Solitary Halictid Lasioglossum Zonulum: with Observations on Lasioglossum Leucozonium

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Demography and Molecular Ecology of the Solitary Halictid Lasioglossum Zonulum: with Observations on Lasioglossum Leucozonium Demography and molecular ecology of the solitary halictid Lasioglossum zonulum: With observations on Lasioglossum leucozonium Alex N. M. Proulx, M.Sc. Biological Sciences (Ecology and Evolution) Submitted in partial fulfillment of the requirements for the degree of Master of Science Faculty of Mathematics and Science, Brock University St. Catharines, Ontario © 2020 Thesis Abstract Halictid bees are excellent models for questions of both evolutionary biology and molecular ecology. While the majority of Halictid species are solitary and many are native to North America, neither solitary nor native bees have been extensively studied in terms of their population genetics. This thesis studies the social behaviour, demographic patterns and molecular ecology of the solitary Holarctic sweat bee Lasioglossum zonulum, with comparisons to its well-studied sister species Lasioglossum leucozonium. I show that L. zonulum is bivoltine in the Niagara region of southern Ontario but is univoltine in a more northern region of southern Alberta. Measurements of size, wear and ovarian development of collected females revealed that Brood 1 offspring are not altruistic workers and L. zonulum is solitary. A large proportion of foundresses were also found foraging with well-developed ovaries along with their daughters, meaning L. zonulum is solitary and partially-bivoltine in the Niagara region. L. zonulum being solitary and univoltine in Calgary suggests that it is a demographically polymorphic and not socially polymorphic. Thus, L. zonulum represents a transitional evolutionary state between solitary and eusocial behaviour in bees. I demonstrate that Lasioglossum zonulum was introduced to North America at least once from Europe in the last 500 years, with multiple introductions probable. Most North American specimens share the same mitochondrial DNA haplotype as those in Europe, with a small portion from western North America possessing distinct sequences. Investigations using microsatellite markers found North American populations to have a deficit of heterozygosity, and Bayesian i analysis suggests that there are 3-4 lineages of L. zonulum in North. It is theorized that introductions could also be from Europe, Asia, or could even represent a native population which arrived via the Bering Land Bridge. I suggest that the plasticity found in L. zonulum may have a genetic cause and exists in North America due to the multiple introductions and potentially diverse geographic origins of this species. The outcome of my studies highlight why Lasioglossum zonulum is a model organism for the study of how eusociality evolved and why it warrants further and more in-depth study. ii Acknowledgments I will start by thanking my supervisor Dr. Miriam Richards. You have been an amazing mentor, and I can’t thank you enough for drawing me back into science with your collection of flashy bees. You helped me out every step of the way and were there to help me pick up the pieces as I ran into every obstacle in the book (and I mean EVERY obstacle). You pushed me to be a better scientist, which I hated at the time but am so grateful for now. Thank you for all the guidance, support, and helping me to laugh at myself when I’m being ridiculous. Many thanks to my supervisory committee members Dr. Fiona Hunter and Dr. Alan Castle. Your contributions of time, helpful advice, and expertise in improving my thesis helped me to finish this beast nearly on time. I have watched the Brock Bee Lab grow substantially from when I started as a research assistant, and each member deserves a huge thank you for putting up with my eccentricities over the last 2 and a half years. Dave was a huge help when it came to “remembering how to science” and has continued to be a friend and mentor passed his graduation. Lyndon and Jessie have both been amazing in helping to edit my work, helping me to stay on track and keep my sanity. Nora, Madiha and Lyllian have all given me amazing advice and encouragement throughout my journey. I need to thank the generous scientists who donated specimens to me when I reached out to them: Dr. Villu Soon from the University of Tartu, Dr. Paul Galpern and John Swann from the University of Calgary, Dr. Steven Falk, and Dr. Cory Sheffield from the Royal Saskatchewan Museum. Thank you so much for putting in the time and effort to make my research possible Finally, and most importantly, I would like to thank my family, my partner Maggie and our baby Molly. Maggie, you have stuck with me through the good, the bad, and the ugly. I can’t comprehend how you managed to work full time and pick up the slack in our lives while I focused on writing. I am so lucky to have you in my life, and I doubt I could have finished this degree without your constant love, support, and laughing at my dumb jokes. I will always be thankful. To my mother, my father and my sister, thank you for letting me vent, thank you for calling me out when I was stupid, and thank you for your unconditional love. iii Table of Contents Chapter 1 : General Introduction ............................................................................................... 1 Social Evolution ...................................................................................................................... 1 Sociality in Hymenoptera ................................................................................................... 2 The origin of eusociality in Hymenoptera .......................................................................... 3 A model family for investigating the evolution of eusociality ........................................... 6 Molecular Ecology ................................................................................................................ 10 Population genetic parameters .......................................................................................... 10 Factors affecting gene flow ............................................................................................... 12 Population structure in bee species ................................................................................... 13 Lasioglossum zonulum .......................................................................................................... 14 Thesis objectives ................................................................................................................... 15 Chapter 2 : Inferring the phenology and behaviour of two Lasioglossum species from pan trap data ....................................................................................................................................... 17 INTRODUCTION................................................................................................................... 18 Objectives ............................................................................................................................. 23 METHODS .............................................................................................................................. 25 Study Sites ............................................................................................................................ 25 Collections ............................................................................................................................ 25 Inferring Phenology .............................................................................................................. 27 Measuring size, wear, and ovarian development .................................................................. 28 Inferring social behaviour ..................................................................................................... 29 Data analysis ......................................................................................................................... 30 RESULTS ................................................................................................................................ 31 Lasioglossum leucozonium from Niagara ............................................................................. 31 Phenology ......................................................................................................................... 31 Lasioglossum zonulum from Niagara.................................................................................... 32 iv Phenology ......................................................................................................................... 32 Inferring sociality with traits of foraging females ............................................................ 34 Lasioglossum zonulum from Calgary.................................................................................... 36 Phenology ......................................................................................................................... 36 DISCUSSION .......................................................................................................................... 38 Partial bivoltinism and demographic polymorphism of Lasioglossum zonulum .................. 39 Lasioglossum zonulum compared to other solitary bivoltine halctines ................................ 40 Demographic polymorphism of Lasioglossum zonulum....................................................... 43 Solitary univoltine nature of Lasioglossum leucozonium ..................................................... 45 Conclusions ..........................................................................................................................
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