Evolutionary Dynamics in Microbial Communities

Underneath the fascinating biology, evolution is governed by a stochastic dynamical process, which describes how mutations arise and spread through a population. Though the basic rules of this process are simple, it is often surprisingly difficult to predict how they combine to determine the genetic composition of a population. In the first part of my talk, I will discuss some key challenges involved in modeling evolutionary dynamics from a statistical physics perspective, along with recent theoretical advances that allow us to predict these dynamics in simple models of genome evolution. I will then discuss our recent experimental effort to measure the dynamics of molecular evolution in a 60,000-generation experiment in E. coli, by sequencing the metagenomes of its frozen “fossil record”. The second part of my talk will focus on a key finding that emerged from this study: the spontaneous evolution of primitive ecological interactions and the breakdown of competitive exclusion. I will introduce a simple, empirically motivated model for describing these coupled ecological and evolutionary processes, which allows us to understand the dynamic balance between the creation of new “species” and the tendency for fitter strains to take over the population.