Okinawa Institute of Science and Technology Graduate UniversityDoctor of PhilosophyMicrobial populations live and grow in spatially structured environments. These structures lead to spatial patterns in populations and alter the course of their natural evolution. Such phenomena are theoretically studied using spatially explicit models. However, these models are still poorly understood due to their analytical and numerical complexity. In this thesis, we study two systems of microorganisms living and proliferating in different spatially structured environments. The first system consists of populations of Escherichia coli growing in rectangular microchannels with two open ends. We study such populations with a lattice model in which cells shift each other along lanes as they reproduce. The model predicts rapid diversity loss along the lanes, with neutral mutations appearing in the middle of the channel being the most likely to fixate. These theoretical predictions are in agreement with our experimental observations. The second system is constituted by planktonic microorganisms that are transported by chaotic oceanic currents. To replicate their dynamics, we employ an individual-based coalescence model. The model predicts the effect of oceanic currents on the biodiversity of planktonic communities, as observed in metabarcoding data sampled from oceans and lakes around the world.doctoral thesi
