Letter | Published:

Disentangling nestedness from models of ecological complexity

Nature volume 487, pages 227230 (12 July 2012) | Download Citation

Abstract

Complex networks of interactions are ubiquitous1 and are particularly important in ecological communities, in which large numbers of species exhibit negative (for example, competition or predation) and positive (for example, mutualism) interactions with one another. Nestedness in mutualistic ecological networks is the tendency for ecological specialists to interact with a subset of species that also interact with more generalist species2. Recent mathematical and computational analysis has suggested that such nestedness increases species richness3,4. By examining previous results and applying computational approaches to 59 empirical data sets representing mutualistic plant–pollinator networks, we show that this statement is incorrect. A simpler metricthe number of mutualistic partners a species hasis a much better predictor of individual species survival and hence, community persistence. Nestedness is, at best, a secondary covariate rather than a causative factor for biodiversity in mutualistic communities. Analysis of complex networks should be accompanied by analysis of simpler, underpinning mechanisms that drive multiple higher-order network properties.

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Acknowledgements

We thank D. Franks, D. Kelly, R. Law, D. Stouffer, C. Thomas and J. Tylianakis for discussions and constructive criticisms, and J.Williams for independent verification of numerical results. M.J.P., A.J. and J.W.P. were supported by the Royal Society of New Zealand Marsden Fund, grant number 08-UOC-034. J.W.P. acknowledges the support of the University of Canterbury Erskine Programme.

Author information

Affiliations

  1. Biomathematics Research Centre, University of Canterbury, Private Bag 4800, Christchurch 8040, New Zealand

    • Alex James
    •  & Michael J. Plank
  2. York Centre for Complex Systems Analysis, and Departments of Biology and Mathematics, University of York, Heslington, York YO10 5DD, United Kingdom

    • Jonathan W. Pitchford

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Contributions

All authors contributed equally to this work.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Alex James.

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    Supplementary Information

    This file contains Supplementary Text and Data, Supplementary Tables 1-2, Supplementary Figures 1-8 and Supplementary References.

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https://doi.org/10.1038/nature11214

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