Date of Award
Doctor of Philosophy (PhD)
Two challenging goals of evolutionary biology are to understand how evolutionary innovations evolve and how they contribute to the success of lineages. Evolutionary innovations may arise following whole genome duplication (WGD) events and they are suspected to contribute to the success of lineages by creating ecological opportunity. However, direct evidence for duplicated genes involved in evolutionary innovations remains rare, and the relationship between evolutionary innovations and the success of lineages may be very complex. In this study, I explore the relationship of evolutionary innovation, WGD, and the ecological dominance of yeast species in high-sugar environments. In budding yeast, a major evolutionary transition occurred around the time of a WGD that dramatically changed the way yeast species harness energy. Whereas most yeast species acquire energy through aerobic respiration, post-WGD yeast species such as Saccharomyces cerevisiae acquire most of their energy via fermentation. Evolution of the fermentative lifestyle may have required duplicated genes and is suspected to contribute to the ecological dominance of yeast species in high-sugar environments. Direct evidence for the role of duplicated genes involved in this evolutionary innovation remains rare, and it is difficult to know whether dominance in high-sugar environments was a direct consequence of this evolutionary transition or depends upon the acquisition of additional traits. The objectives of this research were to obtain direct evidence that duplicated genes contribute to the fermentative lifestyle, determine when ecological dominance in high-sugar environments evolved in the yeast lineage, and to identify traits that contribute to the dominance of S. cerevisiae in high-sugar environments. In Chapter 1, I provide direct evidence that the duplicated genes TOM70 and TOM71 are both required for a trait that evolved during the transition to a fermentative lifestyle. In Chapter 2, I determine that ecological dominance evolved very recently in the yeast lineage and identify multiple fitness traits related to pH, nutrients, and ethanol that contribute to the dominance of S. cerevisiae in high-sugar environments. Overall, the findings from this study advance the field of evolutionary biology by providing direct evidence that duplicated genes retained following WGD contribute to an evolutionary innovation and showing that the ecological success of some lineages may not be an immediate consequence of evolutionary innovation but involves the acquisition of multiple fitness traits.
Chair and Committee
Yehuda Ben-Shahar, Barak Cohen, Allan Larson, Kenneth Olson, Barbara Schaal
Williams, Kathryn Marie, "Evolution of Ecological Dominance of Yeast Species in High-Sugar Environments" (2014). Arts & Sciences Electronic Theses and Dissertations. 340.