Microbes are found ubiquitously throughout nature, displaying an extreme amount of diversity. Microbes are also known to behave in a variety of complex social interactions via chemical signaling. These allow for more complex interaction than that of just competitive exclusion. One common interaction is a public goods interaction, where some member of the population invest metabolic costs into the production of a public good, often an enzyme, whose action benefits all population members in the vicinity, regardless of whether they paid the same metabolic costs. While the public goods game has traditionally been studied in an evolutionary context, in microbial populations evolutionary and ecological timescales overlap. This implies potential feedback between evolutionary effects and ecological effects. In this thesis I discuss a theoretical model for studying these questions. Then I demonstrate a general tradeoff a cooperative population faces between how resilient they are to ecological pressures like demographic fluctuations and evolutionary pressures like invasion from freeloaders. Finally, I investigate the conditions under which a diversity of cooperating and freeloading species can arise under evolution. I show how when the model is adjusted from a well mixed to a spatially extended environment, the range of parameters for which one expects diversification also expands. Finally, in a spatially extended environment I observe a transient but prolonged spatial partitioning of the populations due to the presence of two distinct timescales for the population growth. These results indicate how ecology and evolution can interact to produce complex microbial communities like the ones observed in nature.
|Commitee:||Fraden, Seth, Fai, Thomas|
|School Location:||United States -- Massachusetts|
|Source:||DAI-B 81/4(E), Dissertation Abstracts International|
|Subjects:||Biophysics, Microbiology, Mathematics|
|Keywords:||Ecology, Evolution, Microbial community, Public goods game|
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