ECOLOGICAL AND EVOLUTIONARY DYNAMICS OF PLANT-SOIL FEEDBACKS: INFLUENCES ON EVOLUTION AND RANGE DYNAMICS

Plants interact with, modify, and are affected by their soil environments. Though plant-soil interactions are well known to be important and active regulators of ecosystem function and community structure, much less is known about how these interactions affect plant evolution. The primary goal of my dissertation was to examine plant-soil interactions under a range of ecological and evolutionary contexts to better understand patterns of biodiversity, ecosystem function, and whole system responses to environmental change. Taking such an eco-evolutionary perspective allows for a holistic understanding of the causes and consequences of complex abiotic and biotic interactions that link ecosystem ecology and evolution.

In my first chapter, I reviewed what is known about genetic interactions between plants, soils, and soil communities, and in doing so, identified a new mechanism for how genetically based plant-soil feedbacks might emerge at large scales. In my second chapter, I used field observations and multiple experimental approaches to test whether soil N acts as a selective gradient on plant phenotypes, if soil microbial communities mediate the selective pressure, and whether plant genetic variation impacts soil N pools. In my third chapter, I developed climate and soil ecological niche models, combined with a new double quantile regression approach, to tests how traits are adapted or plastic at critical environmental limits. Finally, my fourth chapter examined how plant-soil interactions and feedbacks at landscape scales may influence range dynamics and associated ecosystem processes as species move upwards towards higher elevations with rising temperatures. Overall, my dissertation sought to bring an evolutionary perspective to ecosystem ecology research by investigating the genetic mechanisms and outcomes of plant-soil interactions.