Transient dynamics and counterintuitive competitive performance in periodic environments

Despite the rapid pace of global change altering temporal environmental patterning, we lack a general understanding of how periodic environments structure ecological communities. In fluctuating environments, nonlinear dynamics associated with temporal trade-offs between competing species can create the potential for both niche differentiation (coexistence) and seemingly unexpected outcomes (exclusion) that deviate from deterministic coexistence theory. Yet, the mechanisms behind these outcomes are not fully understood. Here, we show that periodic fluctuations between times of high and low growth (e.g., seasons), and adaptive temporal trade-offs within and between species, can drive counterintuitive over- and under-performance of competing species. Most notable is the counterintuitive outcome of seasonally-mediated competitive exclusion that would not occur in either season alone, but is rather the direct result of environmental variability itself. We find that seasonal trade-offs in species’ growth rates, seasonal differences in competition strength, and functional similarity between competing species have the potential to drive nonlinear responses in coexistence to changing seasonality under global change. These biological conditions collectively influence our model’s transient dynamics, further explaining the mechanisms behind counterintuitive outcomes and highlighting the importance of non-equilibrium theory for global change ecology. Importantly, the seasonal patterns and species’ trade-offs that magnify these results are biologically realistic, therefore providing important insight into the implications for the maintenance of biodiversity under global change.