Emergent predictability in microbial ecosystems

A long-standing hypothesis of microbial ecology is that simple patterns might persist despite community complexity or even emerge because of it. However, the concept of "emergent simplicity" remains partly intuitive. Here, we defined emergent predictability of microbial ecosystems based on the predictive power of coarsened descriptions that group individual microbial strains into broader classes. We used two published datasets to show that coarse descriptions became more predictive for more species-rich communities. This behavior was not explained by simple averaging effects in large communities. To the contrary, our analysis indicates that emergent predictability arises when physiological or environmental feedback counteracts these averaging effects along certain axes of community variation, allowing these axes to become more informative as diversity increases.