Data from: Soil microarthropod communities along salt marsh transects of the Wadden Sea are predominantly structured by niche differentiation

The relative importance of deterministic versus stochastic processes in
community assembly is widely discussed in ecology. Stochastic models
explain community assembly by ignoring the niches of species, whereas
deterministic models assume the niche concept to be key for understanding
the assembly of species. Whether stochastic or deterministic processes
dominate in shaping the community composition of soil animals is gaining
increased attention. Here, we investigated the spatial heterogeneity of
soil microarthropod communities (Collembola, Oribatida, Mesostigmata)
along a salt marsh transect from the upper salt marsh (USM) to the lower
salt marsh (LSM) to the pioneer zone (PZ) on three islands, i.e.,
Norderney, Spiekeroog, and Wangerooge, in the Wadden Sea of Germany. We
hypothesized that microarthropod communities are predominantly structured
by niche-based processes and change in a deterministic way from the USM to
the LSM to the PZ, whereas microarthropod communities differ little
between the three islands of similar history and position in the Wadden
Sea. Supporting our hypothesis, Oribatida and Mesostigmata communities
differed more strongly between the three zones than between the islands,
indicating that environmental factors changing along the salt marsh
gradient select for specific mite communities in a deterministic way.
Collembola communities also differed between the three zones,s but also
between the islands, indicating that they are structured by both
environmental filtering as well as stochasticity. However, even the
differences in mite and Collembola communities between the islands may -
at least in part - be explained by environmental filtering, e,.g. by
differences in nutrient input from the Ems river estuarine. Overall, the
results indicate that stochasticity plays only a limited role in
structuring microarthropod communities in the dynamic marine – terrestrial
boundary of salt marshes, pointing to the importance of niche
differentiation and environmental filtering.