Date of Completion
ecology, evolutionary biology, climate change, functional traits, common garden, herbarium, phenology, species distribution modeling, MaxEnt, South Africa
Dr. Kent E. Holsinger
Dr. Carl D. Schlichting
Dr. Elizabeth L. Jockusch
Field of Study
Ecology and Evolutionary Biology
Doctor of Philosophy
Climate change is causing major shifts in species distributions, which fundamentally alters the species composition and functioning of biological communities across the globe. Projections suggest that by 2100 up to one of every six species will become extinct. Such drastic changes will have significant impacts on biodiversity patterns and ecosystem functioning. Ecologists are faced with the pressing work of trying to understand how plants will respond to changing and increasingly stressful environments. To predict the long-term effects and magnitude of species responses, it is imperative that species adaptive responses are understood across the entirety of their geographic ranges. My dissertation employs an integrative approach to study the mechanisms driving interactions between functional traits, current and future distributions, historic phenological shifts, and species survival in changing environments. I use the highly diverse and charismatic flowering plant genus, Pelargonium L’Hér., as my model system.
Chapter 1 assesses whether mean annual temperatures and flowering times have changed over the century and if the changes are correlated. This phenology study provides evidence of historic responses to climate change and highlighted shifts in flowering phenology associated with increases in temperatures.
Chapter 2 uses common gardens to understand how species would respond to novel environments they are projected to face in the future, and identify traits related to fitness. Species exhibited significant differences among traits and across gardens, suggesting that plasticity may have a role in aiding species persistence.
Lastly, Chapter 3 evaluates the relationship between environmental predictors and species occurrences using the principle of maximum entropy and then forecasts habitat suitability into the future. Results showed a wide range of responses, with most species ranges shifting towards more hot and dry conditions, which suggests species may find themselves in unfavorable conditions if they are not able to adapt or be plastic.
My research strengthens our understanding of plastic responses along an environmental gradient, assesses intraspecific and interspecific variation, identifies key indicator traits needed for species adaptability, forecast species range responses, and provides the practical framework for conservation protection and management in the highly diverse ecosystems found in South Africa.
Williams, Tanisha Marie, "Predicting Pelargonium Responses to Climate Change in a Biodiversity Hotspot throughout South Africa" (2019). Doctoral Dissertations. 2257.