Emergent evolutionary forces in spatial models of luminal growth in the human gut microbiota

 The spatial organization of microbial communities can strongly influence their ecological and evolutionary dynamics. Previous work has shown that gut microbiota are structured over a range of length- and time-scales. Yet little is known about how this heterogeneity impacts the long-term genetic turnover of these communities. In this talk, we describe a mathematical framework which demonstrates how evolutionary forces emerge from simple models of growth in the intestinal lumen. Our model shows how fluid flow and nutrient availability combine to shape the frequencies of mutations in sequenced fecal samples, yielding quantitative estimates for the effective selection strengths, generation times, and rates of genetic drift. These results provide a starting point for understanding the evolution of the gut microbiota in its native context.