Environmental Heterogeneity and the Maintenance of Diversity, and the Prioritization of Diversity

Biodiversity in two parts: environmental heterogeneity and the maintenance of diversity, and the prioritization of diversity by Caroline Marie Tucker A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Ecology and Evolutionary Biology University of Toronto © Copyright by Caroline M. Tucker 2013 Biodiversity in two parts: environmental heterogeneity and the maintenance of diversity, and the prioritization of diversity Caroline Marie Tucker Doctor of Philosophy Ecology and Evolutionary Biology University of Toronto 2013 Abstract Questions surrounding the causes and consequences of diversity lie at the centre of community ecology. Understanding the mechanisms by which species diversity is maintained motivates much experimental and theoretical work, but this work often focuses on fluctuation-independent mechanisms. Variability in habitat suitability is ubiquitous through space and time however, and provides another important path through which species diversity can be maintained. As a result, considering environmental variability has value for conservation and management. Finally, differences through space and time in the mechanisms that promote and maintain diversity produce spatially varying patterns of diversity. Spatial variation in different forms of diversity (species (SR), phylogenetic (PD), and functional diversity (FD)) creates difficult decisions about prioritization and reserve locations. This thesis uses experimental, observational, and theoretical methods to explore the causes and consequences of diversity. I show that variation in space and time has important implications for species coexistence and diversity maintenance. In microbial nectar communities, temperature variation through space and time alters the importance ii of priority effects on community assembly. Using models of warming temperatures in annual plant communities I show that considering temporal partitioning of flowering (a strategy to minimize competition) introduces constraints on phenological shifts: this has implications for phenological monitoring programs. Finally, I show that variability in the timing of fire events in Mediterranean shrublands contributes to coexistence between life forms, suggesting that it should be considered for fire management. In the final two chapters, I focus on conservation prioritization. Comparisons of species richness and evolutionary diversity through space in the Cape Floristic Region of South Africa show that existing reserves protect Proteaceae richness, but fail to capture evolutionary distinct species. More generally, in the final chapter I suggest that SR and PD should be congruent through space when species are of similar ages, regions are depauperate, or ranges are discontinuous. iii Acknowledgments Above all, many thanks to my supervisor Marc Cadotte, who was good Samaritan, Cheerleader and Sage all along. Without his support this degree wouldn’t have had a middle or an end. Thanks to my extended lab family for all the support and general good times they have provided: Lanna Jin, Nick Mirotchnick, Kelly Carscadden, Stuart Livingstone, and Carlos Arnillas. In no particular order, thanks to all the faculty members who were incredibly generous with their time and expertise including Peter Abrams, Ben Gilbert, T.J. Davies, Art Weis, Marie-Josee Fortin and Tadashi Fukami. Equally valuable were the fellow grad students who shared their knowledge with me, especially Josie Hughes, Stephen Walker, Dak de Kerckhove, and Jordan Pleet. In addition, thanks to my Scarborough cohort (Maria Modanu, Emily MacLeod, Devin Bloom, and Tiffany Schriever), who were sources of constant peer support. For their constant support, Anna, John, and Michael Tucker have played a special role in my success, and will continue to do so in the future. My gratitude to Anna Tucker and Patrick Tucker who introduced me to the world of plants and nature. Finally, thank you to my committee members: Helene Wagner, Ben Gilbert, Don Jackson for patiently letting me find my feet as a scientist. iv Table of Contents Acknowledgments.......................................................................................................................... iv Table of Contents............................................................................................................................ v List of Figures................................................................................................................................ ix List of Appendices ........................................................................................................................ xii Introduction: Understanding patterns of diversity .......................................................................... 1 References....................................................................................................................................... 9 Chapter 1 Environmental Variability Counteracts Priority Effects to Facilitate Species Coexistence: Evidence from Nectar Microbes......................................................................... 13 1 1................................................................................................................................................ 13 1.1 Abstract............................................................................................................................. 13 1.2 Introduction....................................................................................................................... 13 1.3 Methods............................................................................................................................. 15 1.3.1 Study organisms.................................................................................................... 15 1.3.2 Experimental flowers............................................................................................ 16 1.3.3 Experimental design.............................................................................................. 16 1.3.4 Dispersal between flowers .................................................................................... 17 1.3.5 Population density estimation............................................................................... 18 1.3.6 Supplementary experiments.................................................................................. 18 1.4 Results............................................................................................................................... 19 1.5 Discussion......................................................................................................................... 20 1.6 Acknowledgements........................................................................................................... 22 References..................................................................................................................................... 23 Figures........................................................................................................................................... 25 Appendices.................................................................................................................................... 29 v Chapter 2 Community-level interactions alter species responses to climate change.................... 33 2 2................................................................................................................................................ 33 2.1 Abstract............................................................................................................................. 33 2.2 Introduction....................................................................................................................... 34 2.3 Model and Results............................................................................................................. 35 2.3.1 Model .................................................................................................................... 35 2.3.2 Simulations ........................................................................................................... 37 2.3.3 Results................................................................................................................... 39 2.4 Discussion......................................................................................................................... 40 2.5 Acknowledgements........................................................................................................... 43 References..................................................................................................................................... 44 Figures........................................................................................................................................... 48 Appendices.................................................................................................................................... 53 Chapter 3 Fire variability, as well as frequency, can explain coexistence between seeder and resprouter life histories........................................................................................... 57 3 3................................................................................................................................................ 57 3.1 Abstract............................................................................................................................. 57 3.1.1

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