Data from: Metacommunity structure of stream insects across three hierarchical spatial scales

A major challenge in community ecology is to understand the underlying
factors driving metacommunity (i.e. a set of local communities connected
through species dispersal) dynamics. However, little is known about the
effects of varying spatial scale on the relative importance of
environmental and spatial (i.e. dispersal related) factors in shaping
metacommunities and on the relevance of different dispersal pathways.
Using a hierarchy of insect metacommunities at three spatial scales (a
small, within-stream scale, intermediate, among-stream scale, and large,
among-sub-basin scale), we assessed whether the relative importance of
environmental and spatial factors shaping metacommunity structure varies
predictably across spatial scales, and tested how the importance of
different dispersal routes vary across spatial scales. We also studied if
different dispersal ability groups differ in the balance between
environmental and spatial control. Variation partitioning showed that
environmental factors relative to spatial factors were more important for
community composition at the within-stream scale. In contrast, spatial
factors (i.e. eigenvectors from Moran’s eigenvector maps) relative to
environmental factors were more important at the among-sub-basin scale.
These results indicate that environmental filtering is likely to be more
important at the smallest scale with highest connectivity, while dispersal
limitation seems to be more important at the largest scale with lowest
connectivity. Community variation at the among-stream and among-sub-basin
scales were strongly explained by geographical and topographical
distances, indicating that overland pathways might be the main dispersal
route at the larger scales among more isolated sites. The relative effect
of environmental and spatial factors on insect communities varied between
low and high dispersal ability groups; this variation was inconsistent
among three hierarchical scales. In sum, our study indicates that spatial
scale, connectivity and dispersal ability jointly shape stream
metacommunities.