Drought mediates the importance of stochastic community assembly. Jonathan M. Chase explores how drought influences the relative importance of stochastic ecological drift and priority effects in community assembly. He conducted a long-term experiment with artificial ponds to examine how community composition varies with and without drought. He found that in ponds without drought, community composition varied significantly due to stochastic processes, while in drought-affected ponds, community composition was more similar, likely due to niche selection filtering out species that could not tolerate harsh conditions. These results suggest that the harshness of the environmental filter determines whether stochastic or deterministic processes dominate in community assembly. Drought acts as a strong environmental filter, reducing the number of species that can persist, leading to more predictable community compositions. The study highlights the role of environmental filters in shaping biodiversity patterns and emphasizes the need to consider both stochastic and deterministic processes in understanding community assembly. The findings have implications for biodiversity conservation and restoration, as they show that environmental stressors like drought can significantly influence community structure and diversity. The study also underscores the importance of considering spatial and temporal scales when examining biodiversity patterns.Drought mediates the importance of stochastic community assembly. Jonathan M. Chase explores how drought influences the relative importance of stochastic ecological drift and priority effects in community assembly. He conducted a long-term experiment with artificial ponds to examine how community composition varies with and without drought. He found that in ponds without drought, community composition varied significantly due to stochastic processes, while in drought-affected ponds, community composition was more similar, likely due to niche selection filtering out species that could not tolerate harsh conditions. These results suggest that the harshness of the environmental filter determines whether stochastic or deterministic processes dominate in community assembly. Drought acts as a strong environmental filter, reducing the number of species that can persist, leading to more predictable community compositions. The study highlights the role of environmental filters in shaping biodiversity patterns and emphasizes the need to consider both stochastic and deterministic processes in understanding community assembly. The findings have implications for biodiversity conservation and restoration, as they show that environmental stressors like drought can significantly influence community structure and diversity. The study also underscores the importance of considering spatial and temporal scales when examining biodiversity patterns.