eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. Title: Mechanisms controlling the distribution of two invasive Bromus species Journal Issue: Frontiers of Biogeography, 6(1) Author: Bykova, Olga , University of Toronto Publication Date: 2014 Publication Info: Frontiers of Biogeography Permalink: http://www.escholarship.org/uc/item/6qm9z7r2 Acknowledgements: This PhD project was conducted under the supervision of Professor Rowan Sage and advisory support of Professors Arthur Weis and Tammy Sage. Jeffrey Harsant provided technical support with tiller cell count and GIS mapping. This research was funded by the Ontario Graduate Scholarship, the Centre for Global Change awards and Charles E. Eckenwalder Scholarship in Science and Technology to OB. I would also like to express my sincere gratitude to my collaborators I have met in Frankfurt a. M during the workshops “The Ecological Niche as a Window to Biodiversity” for their support and inspiration. Keywords: freezing tolerance, grasses, invasive species, photosynthesis, reproduction, temperature Local Identifier: fb_18999 Abstract: In order to predict future range shifts for invasive species it is important to explore their ability to acclimate to the new environment and understand physiological and reproductive constraints controlling their distribution. My dissertation studied mechanisms by which temperature may affect the distribution of two aggressive plant invaders in North America, Bromus tectorum and Bromus rubens. I first evaluated winter freezing tolerance of Bromus species and demonstrated that the mechanism explaining their distinct northern range limits is different acquisition time of freezing tolerance. While B. rubens has a slower rate of freezing acclimation that leads to intolerance of sudden, late-autumn drops in temperature below -12°C, B. tectorum rapidly hardens and so is not impacted by the sudden onset of severe late-autumn cold. In addition, the analysis of male reproductive development and seed production showed that neither species produces seed