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Data from: Local and regional drivers of taxonomic homogenization in stream communities along a land use gradient


Budnick, William R. et al. (2019), Data from: Local and regional drivers of taxonomic homogenization in stream communities along a land use gradient, Dryad, Dataset,


Aim: The interaction of land use with local vs. regional processes driving biological homogenization (β-diversity loss) is poorly understood. We explored: i) stream β-diversity responses to land cover (forest vs. agriculture) in terms of physicochemistry and physicochemical heterogeneity, ii) whether these responses were constrained by the regional species pool, i.e. γ-diversity, or local assembly processes through local (α) diversity, iii) if local assembly operated through the regional species abundance distribution (SAD) or intraspecific spatial aggregation, and iv) the dependency on body size, dispersal capacity, and trophic level (producer vs. consumer). Location: United States of America, Canada, and France Time Period: 1993-2012 Major Taxa Studied: Stream diatoms, insects, and fish Methods: We analyzed six datasets totaling 1,225 stream samples. We compared diversity responses to eutrophication and physicochemical heterogeneity in forested vs. agricultural streams with regression methods. Null models quantified contribution of local assembly to β-diversity (β-deviance, βDEV) for both land covers and partitioned it into fractions explained by the regional SAD (βSAD) vs. aggregation (βAGG). Results: Eutrophication explained homogenization and more uneven regional SADs across groups, but local and regional biodiversity responses differed across taxa. βDEV was insensitive to land use. βSAD largely exceeded βAGG and was higher in agriculture. Main Conclusion: Eutrophication but not physicochemical heterogeneity of agricultural streams underlay β-diversity loss in diatoms, insects and fish. Agriculture did not constrain the magnitude of local vs. regional effects on β-diversity, but controlled the local assembly mechanisms. While the SAD fraction dominated in both land covers, it further increased in agriculture at the expense of aggregation. Notably, the regional SADs were more uneven in agriculture, exhibiting excess common species or stronger dominance. Diatoms and insects diverged from fish in terms of biodiversity, SAD shape, and βDEV patterns, suggesting an overriding role of body size and/or dispersal capacity compared to trophic position.

Usage Notes


National Science Foundation, Award: DEB-1745348


United States