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Petermann, Jana S.; Kratina, Pavel; Marino, Nicolas A. C.; MacDonald, A. Andrew M.; Srivastava, Diane S.; Marino, Nicholas A. C.

<b>Abstract</b><br/>Although stochastic and deterministic processes have been found to jointly shape structure of natural communities, the relative importance of both forces may vary across different environmental conditions and across levels of biological organization. We tested the effects of abiotic environmental conditions, altered trophic interactions and dispersal limitation on the structure of aquatic microfauna communities in Costa Rican tank bromeliads. Our approach combined natural gradients in environmental conditions with experimental manipulations of bottom-up interactions (resources), top-down interactions (predators) and dispersal at two spatial scales in the field. We found that resource addition strongly increased the abundance and reduced the richness of microfauna communities. Community composition shifted in a predictable way towards assemblages dominated by flagellates and ciliates but with lower abundance and richness of algae and amoebae. While all functional groups responded strongly and predictably to resource addition, similarity among communities at the species level decreased, suggesting a role of stochasticity in species-level assembly processes. Dispersal limitation did not affect the communities. Since our design excluded potential priority effects we can attribute the differences in community similarity to increased demographic stochasticity of resource-enriched communities related to erratic changes in population sizes of some species. In contrast to resources, predators and environmental conditions had negligible effects on community structure. Our results demonstrate that bromeliad microfauna communities are strongly controlled by bottom-up forces. They further suggest that the relative importance of stochasticity may change with productivity and with the organizational level at which communities are examined.; <b>Usage notes</b><br /><div class="o-metadata__file-usage-entry"><h4 class="o-heading__level3-file-title">protozoa_data.tsv</h4><div class="o-metadata__file-description">This file contains a tab-delimited dataset of all protozoa morphospecies counts, as well as sample and treatment information.</div><div class="o-metadata__file-name"></div><div class="o-metadata__file-name"></div></div><div class="o-metadata__file-usage-entry"><h4 class="o-heading__level3-file-title">protozoa_enviro_data</h4><div class="o-metadata__file-description">This file contains a tab-delimited dataset of all environtmental data taken for all samples, including treatment and sampling identification information. This dataset can be merged with protozoa_data.tsv to reproduce the analyses in Petermann et al.</div><div class="o-metadata__file-name"></div><div class="o-metadata__file-name"></div></div><div class="o-metadata__file-usage-entry"><h4 class="o-heading__level3-file-title">protozoa_variables_explanation.rtf</h4><div class="o-metadata__file-description">This is a text document (rich text format) which contains metadata regarding all the variables in both .tsv files.</div><div class="o-metadata__file-name"></div><div class="o-metadata__file-name"></div></div>

Central America; 10.986376N; Costa Rica; 85.426603W

Dryad version number: 1</p>

Version status: submitted</p>

Dryad curation status: Published</p>

Sharing link: https://datadryad.org/stash/share/rMbebT9HjhsePUD9cbl1sT7-KVzYvhaQuo1ddkqX0vg</p>

Storage size: 201204</p>

Visibility: public</p>

University of British Columbia Library

10.14288/1.0397588

https://doi.org/10.5683/SP2/8XKZOB; https://doi.org/10.5061/dryad.8k55h

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