Speaker
Description
The human gut microbiome harbors astronomical quantities of genetic diversity across evolutionarily distant species. However, it is becoming increasingly apparent that not all contributors towards said diversity are subject to evolutionary dynamics. Rather, genetic variants can be present in a host due to the co-occurrence of multiple genetically diverged lineages of a given species, a form of sub-species ecology known as “strains”. Such complexity raises the question of whether species in the gut exhibit comparable patterns of genetic diversity and, if so, the extent that they can be captured by equivalent dynamics. Viewing the human gut as a statistical ensemble of species, we assessed the extent that quantities of genetic diversity exhibited statistically invariant behavior among species. Leveraging our observations, we identified feasible models of ecological and evolutionary dynamics capable of explaining these patterns through the sole use of parameters estimated from empirical data. An ecological model of strain dynamics provided accurate predictions of the fraction of hosts harboring a given genetic variant among all species, whereas a model of evolutionary dynamics failed. The implications of our results were corroborated by establishing a positive correlation between the accuracy of our predictions and an independent estimate of strain structure across species, providing further evidence that statistical patterns of genetic diversity in the human gut microbiome are predominantly driven by ecological dynamics that arise due to the existence of strain structure. Through these efforts, we establish universality in the empirical patterns and dynamics of genetic diversity in the human gut microbiome.
