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β‐diversity represents the compositional variation among communities from site‐to‐site, linking local (α‐diversity) and regional (γ‐diversity). Researchers often desire to compare values of β‐diversity across localities or experimental treatments, and to use this comparison to infer possible mechanisms of community assembly. However, the majority of metrics used to estimate β‐diversity, including most dissimilarity metrics (e.g., Jaccard's and Sørenson's dissimilarity index), can vary simply because of changes in the other two diversity components (α or γ‐diversity). Here, we overview the utility of taking a null model approach that allows one to discern whether variation in the measured dissimilarity among communities results more from changes in the underlying structure by which communities vary, or instead simply due to difference in α‐diversity among localities or experimental treatments. We illustrate one …