ABSTRACT WALL, WADE ALAN. Population Genetics and Demography of Two Rare Plant Species Endemic to the Longleaf Pine Ecosystem. (Under the direction of William A. Hoffmann and Thomas R. Wentworth.) Astragalus michauxii and Pyxidanthera brevifolia are two rare plant species endemic to the Fall‐line Sandhills region of the Gulf and Atlantic Coastal Plain in the southeastern United States that are currently considered vulnerable to extirpation. The Fall‐line Sandhills, a large area of relictual dunes, are part of the longleaf pine ecosystem, a temperate savanna dominated by Pinus palustris and maintained by frequent fire. The longleaf pine ecosystem covered 37 million hectares across the southeastern United States at the time of European settlement, but land use changes led to the loss or degradation of 97% of the original area. In this dissertation, we used a variety of methods to better understand the biogeography, population genetic structure, and the effects of fire on the population dynamics of A. michauxii and P. brevifolia. Pyxidanthera brevifolia (Diapensiaceae) is an evergreen subshrub that occurs on xeric ridgetops in the Fall‐line Sandhills of North Carolina and South Carolina (USA), with the majority of identified populations occurring on Fort Bragg Military Installation, NC. Fort Bragg is also the only location for the other taxon within the genus, P. barbulata. We developed a germination protocol for P. brevifolia, testing for effects of light and temperature on germination success and rates. Both rates were highest under conditions of low temperature and low light. We used AFLP and cpDNA genetic markers developed for P. brevifolia to assess the taxon’s recent phylogeogeography and taxonomic relationship to P. barbulata. Results indicated there is significant morphological overlap between the two taxa very little genetic differentiation. In addition, evidence suggested that the two taxa did not exhibit any evidence of a range shift following the Pleistocene and that the northern populations of Pyxidanthera were most likely present during the Pleistocene. To investigate the population genetic variation of Astragalus michauxii, we developed eight microsatellites and genotyped 355 individuals across 22 populations. Genetic evidence indicates that within population genetic variation accounts for 92% of the total observed genetic variation and that the species encountered a genetic bottleneck within the past. To explore the influence of fire on the population dynamics of A. michauxii and P. brevifolia, we inventoried established demographic monitoring plots from 2007‐2010. Demographic modeling demonstrated that fire negatively affected both species in the short term by increasing mortality of smaller individuals and reducing fruit set. Results indicated that under simulated annual burning, both species would have reduced population growth rates, and that the “ideal” fire return interval may be 2‐4 years. In summary, while anecdotal evidence suggests that fire is indirectly necessary to maintain an open habitat, A. michauxii and P. brevifolia did not respond as “positively” to fire as might be expected for two species that are endemic to a fire‐dependent ecosystem. However, evidence based on climate data and pollen records indicates that the Fall‐line Sandhills were much colder and drier during the Pleistocene and that there has been a substantial shift in the dominant vegetation. If the two taxa were present in the Fall‐line Sandhills since at least the Pleistocene, they would have experienced much colder and drier conditions and, based on the inferred species composition, a much less frequent fire return interval. In conclusion, while fire may be necessary to maintain an open habitat that may have formerly been maintained climatically, it is not apparent that the two species are “fire‐adapted” in the narrow sense of this term and that a more nuanced use of the concept of fire adaptation may be appropriate. Population Genetics and Demography of Two Rare Plant Species Endemic to the Longleaf Pine Ecosystem by Wade Alan Wall A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Plant Biology Raleigh, North Carolina 2013 APPROVED BY: _______________________________ ______________________________ William A. Hoffmann Thomas R. Wentworth Committee Co‐Chair Committee Co‐Chair ________________________________ ________________________________ Kevin Gross Ignazio Carbone BIOGRAPHY Wade Wall was born in Asheville, NC and spent his formative years in Salt Lake City, UT, and Marion, NC. After attending the University of North Carolina, Chapel Hill, he spent a number years doing a wide range of jobs, including building treehouses, teaching ethics to prisoners, and teaching English to non‐native speakers. In 2005, Wade returned to school at North Carolina State University, obtaining a Master of Science degree in Botany in 2008. He currently lives in Champaign, IL with his wife, Katie, and his son, Asa. ii ACKNOWLEDGMENTS First and foremost, I thank Kathleen Bernadette Coyle, my wife, for her support and understanding during these past few years. Without her by my side I would not have been able to complete this process. My mother and father, Louis and Edna Wall, have always been there for me and I appreciate what they have taught me about how to live a life. Drs. Thomas R. Wentworth and William A. Hoffmann have been sources of inspiration and great role models my years at North Carolina State University. My graduate advisory committee has also been supportive and understanding. Many past and present students of the Plant Biology Department at NC State University have been influential and supportive. In particular, Andy Walker, Renee Marchin, and Kristen Kostelnik provided comic relief and emotional support through the whole process. I will always remember my days in the field with Andy Walker, who will remain a lifelong friend whether he likes it or not. Norm Douglas and Jenny Xiang have been overly patient, teaching me population genetic laboratory and data analysis techniques. The support of Sue Vitello and the Plant Biology departmental staff has been tremendous; without their assistance no graduate student would be able to complete a degree. We all owe them a debt of gratitude that can never be repaid. I am grateful to Matthew Cleary, Brendan Dawal, Jacob Hilton, and Sherrie Emerine for excellent assistance in the field and in the laboratory. They definitely made field work more entertaining. iii Finally, thanks to Matthew G. Hohmann, United States Army Corps of Engineers (ERDC‐CERL), and Janet Gray, Endangered Species Branch, Fort Bragg Military Installation. Without their unwavering support and knowledge, this project would never have been completed. iv TABLE OF CONTENTS LIST OF TABLES .……………………………………………………………………………………………………………………………...vii LIST OF FIGURES ..................................................................................................................................... x CHAPTER 1 OVERVIEW ……………………………………………………………………………………………………………………..1 1.1 Introduction ...................................................................................................................................... 1 1.2 References ........................................................................................................................................ 6 CHAPTER 2 EFFECTS OF LIGHT AND TEMPERATURE ON GERMINATION OF PYXIDANTHERA BREVIFOLIA WELLS (DIAPENSIACEAE) ……………..………………………………………………………………………………..9 2.1 Abstract ............................................................................................................................................ 9 2.2 Introduction .................................................................................................................................... 10 2.3 Methods ......................................................................................................................................... 13 2.4 Results ............................................................................................................................................ 14 2.5 Discussion ....................................................................................................................................... 15 2.6 References ...................................................................................................................................... 19 CHAPTER 3 EVIDENCE FOR RANGE STASIS DURING THE LATTER PLEISTOCENE FOR THE ATLANTIC COASTAL PLAIN ENDEMIC GENUS, PYXIDANTHERA MICHAUX…………………………………………………………24 3.1 Abstract .......................................................................................................................................... 24 3.2 Introduction .................................................................................................................................... 25 3.3 Methods ......................................................................................................................................... 29 3.3.1 Sampling and Morphological Measurements ..................................................................... 29 3.3.2 Molecular methods ............................................................................................................. 30 3.3.3 cpDNA data analysis ............................................................................................................ 31 3.3.4 AFLP