Effect of Temporal Environmental Fluctuations on Microbial Competition

Environmental fluctuations, such as seasonal or diurnal variation, can affect species diversity. A major challenge in ecology is to predict how such disturbances will affect the outcome of interspecies competition. When temporal variation is imposed on additive linear models, such as the Lotka-Volterra competition model, the parameters and variables can be replaced by their time averages. The outcome of a fluctuating environment should therefore be the same as that of a constant environment with the time-averaged parameters and variables, according to these simple models. To test this prediction, we drew from previous results, which showed that increasing mortality shifts pairwise outcomes from dominance of the slow grower at low mortality to dominance of the fast grower at high mortality, with coexistence or bistability at intermediate mortality. By fluctuating between low and high mortality, we were able to produce the time-averaged result: bistability or coexistence. These results argue that simple models can provide powerful insight into how changing environments will lead to changing structure of communities.