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Ecological network complexity scales with area

Abstract

Larger geographical areas contain more species—an observation raised to a law in ecology. Less explored is whether biodiversity changes are accompanied by a modification of interaction networks. We use data from 32 spatial interaction networks from different ecosystems to analyse how network structure changes with area. We find that basic community structure descriptors (number of species, links and links per species) increase with area following a power law. Yet, the distribution of links per species varies little with area, indicating that the fundamental organization of interactions within networks is conserved. Our null model analyses suggest that the spatial scaling of network structure is determined by factors beyond species richness and the number of links. We demonstrate that biodiversity–area relationships can be extended from species counts to higher levels of network complexity. Therefore, the consequences of anthropogenic habitat destruction may extend from species loss to wider simplification of natural communities.

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Fig. 1: Spatial scaling of network complexity.
Fig. 2: Scaling of the number of links with species richness.
Fig. 3: Spatial scaling of mean indegree and network degree distribution.

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Data availability

All datasets analysed during the current study are available online at https://doi.org/10.5061/dryad.zcrjdfndg66, https://github.com/nuriagaliana/Ecological-network-complexity-scales-with-area or https://github.com/mlurgi/global-network-area.

Code availability

Custom code used to perform the analyses are available online at https://doi.org/10.5281/zenodo.5758580, https://github.com/nuriagaliana/Ecological-network-complexity-scales-with-area or https://github.com/mlurgi/global-network-area.

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Acknowledgements

We thank J.-F. Arnoldi, M. Barbier and Y. Zelnik for numerous discussions that improved the quality of this paper. This work was supported by the TULIP Laboratory of Excellence (ANR-10-LABX-41 and 394 ANR-11-IDEX-002-02) to J.M.M., by a Region Midi-Pyrenees project (CNRS 121090) to J.M.M., and by the FRAGCLIM Consolidator Grant (726176) to J.M.M. from the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program. The study was also supported by Spanish MICINN projects CGL2009-12646, CSD2008-0040 and CGL2013-41856 to J.B. and A.R. C.E. was funded through the São Paulo Research Foundation (FAPESP 2015/15172-7). V.A.G.B. was funded by National Funds through FCT—Foundation for Science and Technology under the Project UIDB/05183/2020. W.T. received funding from the ERA-Net BiodivERsA—Belmont Forum, with the national funder Agence National pour la Recherche (FutureWeb: ANR-18-EBI4–0009 and BearConnect: ANR-16-EBI3-0003).

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N.G., J.M.M. and M.L. designed the research with contributions from all co-authors. N.G. and M.L. conducted research and analysed the data. J.B., L.C., B.C.-L., C.E., I.G., C.H.-C., F.J., D.M., C.M., S.O.-C., S.R., A.R., I.S.-D., A.T., D.P.V., S.A.W., T.R. and W.T. contributed the data. J.M.M., V.A.G.B., K.C., M.-J.F., S.J.L., K.M., A.M.M., D.G., T.R., S.V. and W.T. supported research. N.G. and J.M.M. wrote the manuscript with substantial contributions from D.G., T.R. and W.T. and feedback from all co-authors.

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Correspondence to Núria Galiana.

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Galiana, N., Lurgi, M., Bastazini, V.A.G. et al. Ecological network complexity scales with area. Nat Ecol Evol 6, 307–314 (2022). https://doi.org/10.1038/s41559-021-01644-4

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