Committee Chair

Boyd, Jennifer N.

Committee Member

Klug, Hope; Brzyski, Jessica


Dept. of Biological and Environmental Sciences


College of Arts and Sciences


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


The natural world is dynamic, and species must successfully respond to the environmental changes they experience. Pityopsis ruthii (Ruth’s golden aster) is an imperiled endemic perennial confined to boulder crevices along short stretches of the Hiwassee and Ocoee Rivers in Polk County, TN. To investigate plasticity of this species within the context of such change, we used a comparative approach to observe general differences in plasticity between P. ruthii and its widespread congener P. graminifolia by assessing the responses of individuals to experimentally imposed environmental change. Overall, P. ruthii exhibited lower plasticity than P. graminifolia, but these differences were resource-dependent with P. ruthii having significantly greater plasticity within the context of water availability while P. graminifolia exhibited greater plasticity within the context of light availability and temperature. The plasticity differences of P. ruthii and its positive associations with productivity provide context for understanding its constrained distribution and habitat specificity.


Foremost, I would like to thank my advisor Dr. Jennifer Boyd for accepting me into her lab all those years ago and accepting me again as a graduate student. Since then we have moved from student to friends, to colleagues, and now to family. I can’t possibly thank you enough for all the opportunities, advice, help, and joy you’ve brought me over the years. You truly are an amazing scientist and woman and I am so thankful to have you in my life. I would also like to thank Dr. Hope Klug for serving on my committee, providing statistical advice, and treating me as a friend when I needed assistance of any kind. I would also like to thank Dr. Jessica Brzyski for serving on my committee and facilitating multiple aspects of the behind the scenes work of our NSF project. Thank you to Jenny Cruse-Sanders who provided feedback on this thesis and who was always encouraging, kind, and generous with guidance. Also thank you to Mike Bonsall, Jill Anderson, and Carol Baskauf for statistical assistance, lab guidance, and continued work on our project. I’m so glad to have had the opportunity to work under and learn from all of these truly brilliant scientists. Special thanks to Will Rogers whose positive attitude, helpfulness with anything, and advice got me through many field days and beyond. Without your friendship and support, I could not have accomplished any of this. Thank you also to Geoff Call and Adam Dattilo for coordinating field collections, providing data, and answering my numerous questions. Thank you to all of the undergraduates who assisted in lab, but especially Thomas Wiegand and Braley Gentry, who were always there to help no matter what the situation and whom I can now call my brothers. A huge thank you to my graduate partner in crime and best friend Savanna Wooten who helped keep me sane as we both navigated grad school, you have become one of the most important persons in our lives and I can’t wait to see where we are in 20 years. I’d like to again thank my wife Holly who is always in my corner and who kept me going through all of the ups and downs of this process. And last, but definitely not least thank you to my mother for always believing in me and guiding me through life no matter the journey, without you none of this would have been possible and I am eternally grateful.


M. S.; A thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Master of Science.




Compositae; Pheotypic plasticity; Riparian ecology


endemic; ecophysiology; plasticity; relative abundance; Ruth's Golden Aster

Document Type

Masters theses




xi, 49 leaves