Title: Population and evolutionary dynamics during microbial range expansions

Speaker: Dr. Saurabh Gandhi, MIT

Abstract: Spatial population expansions occur across multiple scales, from the expanding geographical range of a species to the growth of tumors and microbial biofilms. Simple models in theoretical ecology explain many emergent properties of range expansions, such as a constant expansion velocity, exponential density profile at the front etc., in terms of organism-level properties such as growth and dispersal rates. Moreover, the evolution and potentially even the survival of an expanding population depends on its genetic diversity, which is also predicted in theory to reduce drastically during range expansions. However, testing these quantitative predictions in natural populations is difficult because of large environmental variability and the inability of replicating historical processes. In my talk, I will describe the use of a microbial model system to gain a deeper understanding of spatial range expansions. In particular, natural populations often show varying levels of within-species cooperative growth, and the strength of this cooperation modulates spatial range expansions and evolution thereof in interesting ways. Our model system allows controlling cooperation in the population and we use it to test these interesting predictions.