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Abstract Studies of stream macroinvertebrates traditionally use sampling methods that target benthic habitats. These methods could underestimate biodiversity if important assemblage components exist outside of the benthic zone. To test the efficacy of different sampling methods, we collected paired reach‐wide benthic and edge samples from up to 10 study reaches in nine basins spanning an aridity gradient across the United States. Edge sampling targeted riparian‐adjacent microhabitats not typically sampled, including submerged vegetation, roots, and overhanging banks. We compared observed richness, asymptotic richness, and assemblage dissimilarity between benthic samples alone and different combinations of benthic and edge samples to determine the magnitude of increased diversity and assemblage dissimilarity values with the addition of edge sampling. We also examined how differences in richness and assemblage composition varied across an aridity gradient. The addition of edge sampling significantly increased observed richness (median increase = 29%) and asymptotic richness (median increase = 173%). Similarly, median Bray–Curtis dissimilarity values increased by as much as 0.178 when benthic and edge samples were combined. Differences in richness metrics were generally higher in arid basins, but assemblage dissimilarity either increased or decreased across the aridity gradient depending on how benthic and edge samples were combined. Our results suggest that studies that do not sample stream edges may significantly underestimate reach diversity and misrepresent assemblage compositions, with effects that can vary across climates. We urge researchers to carefully consider sampling methods in field studies spanning climatic zones and the comparability of existing data sets when conducting data synthesis studies. 

Abstract Intermittent streams are globally ubiquitous and represent a large percentage of stream networks. As climate change in many arid regions increases the frequency and intensity of drying disturbances, it is important to understand how aquatic biota will respond to such disturbances and how it would impact aquatic biodiversity. To address these topics, we sampled 10 stream reaches in the Sycamore Creek basin, an arid‐land stream in central Arizona (USA), with reach‐scale flow regimes ranging from perennial to highly intermittent. We sampled aquatic macroinvertebrates during 4 seasons to explore seasonal variability in community structure through flowing and drying phases. We also collected continuous flow data with remote data loggers to explore the impacts of intermittency and distance to perennial refuges on species richness, taxonomic composition and trait composition. Overall, richness was lower at intermittent reaches than perennial reaches, and richness values increased linearly as flow duration increased. We found no relationship between richness and distance to the nearest perennial refuge. Community assemblages differed significantly by season but were not distinct between perennial and intermittent reaches. Trait composition was also distinct between seasons and flow regimes, with traits such as a lack of diapause, longer life span and predatory feeding behaviours being indicators for perennial reaches. As climate change alters natural flow regimes, understanding the responses of macroinvertebrate community structure to drying disturbances in arid‐land streams can provide insight on aquatic community responses to climate change at larger scales.