Diversity and interaction predict microbial community dynamics
By observing miniature microbial ecosystems, the researchers show that more complex ecological communities — those with greater diversity and stronger interactions — tend to be less stable over time and move between distinct dynamic phases, according to a new study. study. The results offer insight into general ecological principles and demonstrate predictable patterns of diversity and dynamics in ecological communities. Ecological communities of all shapes and sizes – from our own individual microbiomes to the Earth’s rainforests – often harbor large numbers of coexisting species, which together perform important functions. However, these communities are complex and their dynamics are difficult to predict, and studying these relationships in large-scale ecosystems is generally impractical. As a result, key aspects of ecosystem functioning, such as whether a community’s diversity enhances or weakens its stability, remain poorly understood. Using mathematical models and observations of bacterial communities under highly controlled conditions, Jiliang Hu and his colleagues performed a direct test of ecological theory by predicting that simple community-level characteristics, such as diversity and interaction, dictate the behaviors of the community. Hu et al. found that more complex bacterial ecological communities were less stable over time and evolved differently, but predictably, depending on their initial diversity and the strengths of interaction between different species. The authors demonstrate that communities go through distinct phases as diversity or interactions increase, from a stable equilibrium where all species coexist to partial coexistence to persistent and dynamic fluctuations in species abundance. According to the results, communities that fluctuated tended to maintain higher species richness, suggesting that diversity and stability are mutually reinforcing. “Overall, the findings of Hu et al. suggest that ecological communities generally pass through distinct phases as the strength or diversity of interspecific interactions change, in the same way that matter abruptly passes through distinct states when temperature or pressure changes,” write Matthias Huelsmann and Martin Ackermann from a related perspective.