MS Thesis - Nicolas Hawley-Weld

Congratulations Nico for defending your thesis entitled, "Towards Bioengineered Ecosystems: Three Studies in Invasion Biology". 


Invasion biology attempts to predict, across multiple scales and environments, what makes an ecological community vulnerable to invasion by one or more foreign species. In the context of biological engineering, invasion events are of interest both as a design objective, in which the goal is to establish or re-establish one or more species in some ecosystem (e.g. delivery of probiotics or restoration of disturbed habitats), or as the inverse problem in which the goal is to ensure that an ecosytem has low invasibility, which is important in open systems such as algal raceway ponds.

Three separate studies in invasion biology were pursued in this thesis. First, an experimental investigation of the invasibility of traditional sourdough starter cultures was performed. Two invader organisms were tested for their ability to invade a traditionally propagated sourdough starter, and a mathematical model was developed for the bacterial fraction of a wheat flour dough. Second, a computational investigation of the effect of community structure on community invasibility was performed. A simple three-species ecosystem was modeled, and different community structures were probed for their ability to allow a rare species to become abundant as a result of perturbations to the system's parameters. Finally, a phage-bacterium system was modeled, in which either the phage or the bacterium can be considered an invader. Relationships between system parameters were explored visually and potential trade-offs or coupling relationships were elucidated.
Full thesis will be available soon online.