INDIVIDUALISTIC AND PHYLOGENETIC PERSPECTIVES ON PLANT COMMUNITY PATTERNS Jeffrey E. Ott A dissertation submitted to the faculty of the University of North Carolina at Chapel Hill in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology Chapel Hill 2010 Approved by: Robert K. Peet Peter S. White Todd J. Vision Aaron Moody Paul S. Manos i ©2010 Jeffrey E. Ott ALL RIGHTS RESERVED ii ABSTRACT Jeffrey E. Ott Individualistic and Phylogenetic Perspectives on Plant Community Patterns (Under the direction of Robert K. Peet) Plant communities have traditionally been viewed as spatially discrete units structured by dominant species, and methods for characterizing community patterns have reflected this perspective. In this dissertation, I adopt an an alternative, individualistic community characterization approach that does not assume discreteness or dominant species importance a priori (Chapter 2). This approach was used to characterize plant community patterns and their relationship with environmental variables at Zion National Park, Utah, providing details and insights that were missed or obscure in previous vegetation characterizations of the area. I also examined community patterns at Zion National Park from a phylogenetic perspective (Chapter 3), under the assumption that species sharing common ancestry should be ecologically similar and hence be co-distributed in predictable ways. I predicted that related species would be aggregated into similar habitats because of phylogenetically-conserved niche affinities, yet segregated into different plots because of competitive interactions. However, I also suspected that these patterns would vary between different lineages and at different levels of the phylogenetic hierarchy (phylogenetic scales). I examined aggregation and segregation in relation to null models for each pair of species within genera and each sister pair of a genus-level vascular plant iii supertree. Some pairs confirmed predictions, but many others did not, suggesting niche divergence rather than niche conservatism. In the final chapter, I discuss community characterization from a phylogenetic perspective, exploring the possibility of using phylogenetic units in lieu of species in community analysis. I consider scenarios where species may not be optimal units of analysis, such as broad-scale community studies spanning species range limits. In such scenarios, species sharing common ancestry could potentially be merged and treated as a single unit. I present a method for identifying such species that I developed by adding a phylogenetic dimension to species clustering. This method is demonstrated through an analysis of bog and rock outcrop plant communities of the Southern Appalachian Mountains. iv To my grandfather James. A. Ott, scientific thinker and admirer of Southern Utah’s natural wonders v ACKNOWLEDGEMENTS My graduate work at the University of North Carolina would not have been possible without the support of individuals and institutions on both sides of the country. On the North Carolina side, I have had enjoyed working with the UNC Plant Ecology Lab, where many students, staff and post-docs who have provided friendship, technical assistance and a stimulating intellectual atmosphere. My graduate advisor Bob Peet and committee members Peter White, Todd Vision, Aaron Moody and Paul Manos have been helpful, supportive and patient as my research has slowly evolved. I am indebted to numerous field and data workers who have contributed to the Carolina Vegetation Survey, especially Susan Wiser and Brenda Wichmann for their work on Southern Appalachian rock outcrop and bog communities, respectively. I have received financial support from the UNC Graduate School in the form of the Graduate Merit Fellowship and Dissertation Completion Fellowship, as well as from the UNC Biology Department through the Mrs. W.C. Coker Fellowship, the Dr. W.C. Coker Fellowship in Botany, and the Alma Holland Beers Scholarship. In addition, I have held numerous teaching and research assistantships and express appreciation for my mentors Pat Gensel, Jim Massey, Seth Reice, Forbes Boyle, Charles Mitchell, Maria Servedio and Corey Johnson. Beyond professional circles, John and Heather Scott and the local Latter-day Saint community deserve mention for their role in welcoming me and helping me feel at home in North Carolina. vi On the Utah side, I owe much to my long-time mentors E. Durant McArthur and Stewart Sanderson at the Rocky Mountain Research Station Shrub Sciences Laboratory of the U.S. Forest Service, as well as Brigham Young University/Utah Valley University professor Kimball Harper. This trio provided inspiration, encouragement and guidance toward my decision to pursue a doctorate degree. They were also the architects and builders of the 1987-89 Zion National Park vegetation survey that ultimately became a centerpiece of this dissertation. I acknowledge the many workers who contributed to this survey (Harper 1993) as well as the more recent USGS-NPS survey (Cogan et al. 2004) which also proved extremely useful. Zion National Park personnel, notably Elena Robisch, Leslie Courtright, Cheryl Decker and Dave Sharrow, provided assistance and feedback during various stages of my research. Portions of this dissertation were funded through the Rocky Mountain Research Station, inasmuch as I laid the groundwork for Chapters 2 and 4 during the course of summer employment there. My parents C. Eric and Marilyn Ott graciously accommodated me during my frequent visits to my home state, and I wish to pay them special tribute for their unfailing love and support. vii TABLE OF CONTENTS CHAPTER 1: INTRODUCTION ..................................................................................... 1 REFERENCES .................................................................................................................6 CHAPTER 2: INDIVIDUALISTIC SPECIES GROUPS OF ZION NATIONAL PARK ............................................................................................................ 9 ABSTRACT .....................................................................................................................9 INTRODUCTION ..........................................................................................................10 BACKGROUND ............................................................................................................15 Study Area ..................................................................................................................15 BYU-RMRS Vegetation Characterization (Harper et al. 2001) .................................18 USGS-NPS Vegetation Characterization and Mapping (Cogan et al. 2004) .............20 INDIVIDUALISTIC COMMUNITY CHARACTERIZATION: CONCEPTS AND METHODS .....................................................................................22 Conceptual Overview .................................................................................................22 Coalition Clustering and Affinity Calculations (Individualistic Fidelity Analysis) ...24 Affiliation Calculations (Individualistic Constancy and Dominance Analysis) ........27 Environmental Modeling of Coalition Species Group Affinities ...............................28 Quantifying Correspondence with Previously-described Vegetation Units ..............32 RESULTS .......................................................................................................................33 Coalition Species Groups and Their Environmental Affinities ..................................33 Affiliate Species of Coalition Groups ........................................................................41 Correspondence with Previously-described Vegetation Units ...................................43 viii DISCUSSION ................................................................................................................48 Community Continuity and Discreteness ..................................................................49 Coalition Clustering Effects ..................................................................................52 Sampling Issues ....................................................................................................54 Dominant Species, Floristic Patterns and Environmental Interpretations .................58 REFERENCES ...............................................................................................................65 CHAPTER 3: PHYLOGENETIC NICHE OVERLAP IN PLANT COMMUNITIES OF ZION NATIONAL PARK ......................................................... 96 ABSTRACT ...................................................................................................................96 INTRODUCTION ..........................................................................................................97 METHODS ...................................................................................................................100 Study Area and Plant Community Data ..................................................................100 Taxonomic/phylogenetic Data Synthesis ................................................................102 Niche Overlap Calculations .....................................................................................103 Significance Tests ....................................................................................................104 RESULTS AND DISCUSSION ..................................................................................106