Data from: 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 alone (after accounting for the environment), pure environment and
pure space together, and spatially structured environment. Taxonomic
similarity of taxa co-occurring because of environmental and/or spatial
controls or because of unmeasured processes was compared to that of a null
model. Results: Pure environment alone, spatially structured environment,
and pure environment and pure space together explained the greatest
proportion of nodes and edges in the co-occurrence networks of diatom
species and genera, and insect genera. Conversely, pure environment and
pure space together best explained the nodes and edges in the
co-occurrence network of fish species and genera. Co-occurring taxa were
more closely related than the random expectation in all 30 cases. Main
Conclusions: The environment controlled co-occurrences of all groups,
while the influence of space was the strongest in fish, the most
dispersal-limited group in our study. All co-occurring taxa were more
taxonomically related than expected by chance due to environmental or
spatial overlap or unaccounted factors.