Environmental and spatial effects on co-occurrence network size and taxonomic similarity in stream diatoms, insects, and fish

Aim: The influences of environmental and spatial processes on species composition have been at the center of metacommunity ecology. Conversely, the relative importance of these processes for species co-occurrences and taxonomic similarity has remained poorly understood. We hypothesized that at a subcontinental scale, shared environmental preference would be the major driver of co-occurrences across species groups. In contrast, co-occurrences due to shared dispersal history were more likely in dispersal-limited taxa. Finally, we tested whether taxa co-occurring due to similar responses to environmental and spatial processes were more taxonomically similar than expected by chance.
Location: The conterminous United States
Time Period: 1993-2019
Major taxa studied: Stream diatoms, insects, and fish
Methods: We generated co-occurrence networks and developed methodology to determine the proportions of nodes and edges explained by pure environment alone (after accounting for space), pure space..., We obtained data from Passy et al., (2023), including diatoms, insects, and fish, collected from, respectively, 1698, 1700, and 1700 stream sites across the conterminous United States (Fig. S1). Sites were compiled from both the National Water-Quality Assessment (NAWQA) program of the US Geological Survey and the National Rivers and Streams Assessment (NRSA) of the US Environmental Protection Agency, which used similar collection methods (Moulton II et al., 2002; US Environmental Protection Agency, 2013). Streams were sampled between 1993 and 2019, with the majority of samples collected between 2007 and 2010. Diatoms and insects were collected from a predetermined area of substrate from May to September. Fish were sampled throughout the year using backpack electrofishing and seining. Community data consisted of counts of species or a lower taxonomic category in diatoms and fish, but genera in insects. To standardize the sampling effort, diatom counts were sampled down to 400 cells, and ..., , # Data from: Environmental and spatial effects on co-occurrence network size and taxonomic similarity in stream diatoms, insects, and fish

[https://doi.org/10.5061/dryad.j3tx95xq6](https://doi.org/10.5061/dryad.j3tx95xq6)

## Description of the data and file structure

We provide species by site matrices for 5 metacommunities of diatoms (species and genera), insects (genera), and fish (species and genera), in the files named “‘Taxon’ Dataset.csv”. We obtained these data from Passy *et al.*, (2023), including diatoms, insects, and fish, collected from, respectively, 1698, 1700, and 1700 stream sites across the conterminous United States (Fig. S1). Sites were compiled from both the National Water-Quality Assessment (NAWQA) program of the US Geological Survey and the National Rivers and Streams Assessment (NRSA) of the US Environmental Protection Agency, which used similar collection methods (Moulton II *et al.*, 2002; US Environmental Protection Agency, 2013). Streams were sampled betwee...