Species interactions limit the predictability of community responses to environmental change

<b>Abstract</b><br/><p>Predicting how ecological communities respond to environmental change is challenging, but highly relevant in this global change era. Ecologists commonly use current spatial relationships between species and environmental conditions to make predictions about the future. This assumes that species will track conditions by shifting their distributions. However, theory and experimental evidence suggest that species interactions prevent communities from predictably tracking temporal changes in environmental conditions, based on current spatial relationships between species and environmental gradients. We tested this hypothesis by assessing the dynamics of protist species in replicated two-patch microcosm landscapes that experienced different regimes of spatial and temporal environmental heterogeneity (light vs. dark). Populations were kept in monoculture or polyculture to assess the effect of species interactions. In monoculture, abundances were predictable based on current environmental conditions, regardless of whether they had experienced temporal environmental change. But, in polyculture, abundances depended also on the history of environmental conditions experienced. This suggests that, because of species interactions, communities should respond differently to spatial versus temporal environmental change. Thus, species interactions likely reduce the accuracy of predictions of future communities that are based on current spatial relationships between species and the environment. </p>