Dataset: Foundation species enhance food web complexity through non-trophic facilitation

This dataset contains 58 food web matrices that we reconstructed in seven different ecosystem types using a consistent methodological approach and an additional 29 matrices which were generated by randomly removing species from foundation species-dominated food webs to match the number observed in neighbouring bare systems . Although the abiotic environmental conditions vary widely across the ecosystems in our study, all were typified by the presence of a spatially dominant foundation species that enhances habitat complexity, and mitigates environmental stress . Our study included three coastal ecosystems: (1) intertidal seagrass beds dominated by Zostera noltii in Banc d’Arguin, (Mauritania), (2) cordgrass-dominated (Spartina alterniflora) fringing marshes growing on the cobble beaches of Rhode Island (USA), and (3) intertidal blue mussel beds (Mytilus edulis) in the Wadden Sea (the Netherlands). We also included two freshwater ecosystems: (1) Watermilfoil (Myriophyllum alteniflorum) dominated shallow lakes in a dune slacks with standing water on the Wadden Sea island of Terschelling (the Netherlands), (2) and Water-starwort (Callitriche obtusangula) dominated slow flowing streams (Desselse Nete, Belgium). Finally, we included two terrestrial systems: (1) marram grass-dominated (Ammophila arenaria) dunes at Terschelling, and (2) Spanish moss (Tillandsia usneoides)-dominated live oaks in Georgia (USA). Within each ecosystem we sampled two contrasting habitat types: areas dominated by foundation species and bare areas where the foundation species was absent. In all seven systems we sampled 3 to 6 replicate areas after which dichotomous food webs were constructed for each sampled area. To test whether observed food web modifications by foundation species arose from random or selective non-trophic facilitation of species, links or levels across the trophic network, we randomly removed species from foundation species-dominated food webs to match the average number of species observed in neighbouring bare systems (within a 95%CI). Based on the matrices included in this dataset, we calculated a number of widely used food web metrics per replicate food web. Additional information regarding the methods or results of this dataset can be found in: Borst, A.C.W., W.C.E.P. Verberk, C. Angelini, J. Schotanus, J.W. Wolters, M.J.A. Christianen, E.M. van der Zee, M. Derksen-Hooijberg and T. van der Heide. 2018. Foundation species enhance food web complexity through non-trophic facilitation. PLoS One.

The first Excel workbook contains all the matrices from Foundation species-dominated food webs (FS). The second workbook contains all the matrices from Bare area food webs (BA). And the third workbook contains all matrices generated by random removal of species from the foundation species-dominated food webs. Also the R-script we used for the calculations of a plethora of food web metrics is also included in this dataset.