Hwa Lab, UC San Diego
Figure 2: Successful colonization of different habitats depend on the population’s expansion speed and growth rate. A) An equal mixture of slow and fast swimming bacteria (indicated by different colors) was inoculated at the center of the soft-agar plate. B) After the mixed population had ample time to expand and grow to high densities, the slowest strain (red) dominated at small distances, the fastest strain dominated at the distances far away, with the strain with intermediate speed dominating the intermediate distances. C) Detailed evolution experiments selecting for strains most successful in colonizing different radial distances (d) found the optimal expansion speed (u) to be linear with the selection distance as predicted by the authors’ mathematical analysis.