The most efficient microbial community dominates during community coalescence

Immigration has major impacts on both the structure and function of communities and evolutionary dynamics of populations. While most work on immigration deals with relatively low numbers and diversity of immigrants, this does not capture microbial community dynamics, which frequently involve the coalescence of entire communities. The general consequences, if any, of such community coalescence are unclear, although existing theoretical and empirical studies suggest coalescence can result in single communities dominating resulting communities. A recent extension8 of classical ecological theory may provide a simple explanation: communities that exploit niches more fully and efficiently prevent species from other communities invading. Here, we test this prediction using complex anaerobic microbial communities, for which methane production provides a measure of resource use efficiency at community scale. We found that communities producing the most methane when grown in isolation dominated in mixtures of communities. As a consequence, the total methane production increased with the number of communities used as an inoculum. In addition to providing a practical method for enhancing biogas production during anaerobic digestion, these results are likely to be relevant to many other microbial communities. As such, it may be possible to predictably manipulate microbial community function for other biotechnological processes, health and agriculture.