Understanding the role of parasites in food webs using the group model

Matthew J. Michalska-Smith, Elizabeth L. Sander, Mercedes Pascual, Stefano Allesina

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Parasites are ubiquitous and have been shown to influence macroscopic measures of ecological network structure, such as connectance and robustness, as well as local structure, such as subgraph frequencies. Nevertheless, they are often under-represented in ecological studies due to their small size and often complex life cycles. We consider whether or not parasites play structurally unique roles in ecological networks; that is, can we distinguish parasites from other species using network structure alone? We partition the species in a community statistically using the group model, and we test whether or not parasites tend to cluster in their own groups, using a measure of “imbalance.” We find that parasites form highly imbalanced groups, and that concomitant predation, in which a predator consumes a prey and its parasites, but not the number of interactions, improves the group model's ability to distinguish parasites from non-parasites. This work demonstrates that parasites and non-parasites interact in networks in statistically distinct ways, and that these differences are partly, but not entirely, due to the existence of concomitant predation.

Original languageEnglish (US)
Pages (from-to)790-800
Number of pages11
JournalJournal of Animal Ecology
Issue number3
StatePublished - May 2018
Externally publishedYes

Bibliographical note

Funding Information:
NSF GRFP; U.S. Department of Education grant, Grant/Award Number: P200A150101; NSF, Grant/Award Number: DEB-1148867 and DEB-0553768; National Center for Ecological Analysis and Synthesis

Funding Information:
The authors thank G Barabás, A Dobson, J Dunne, J Grilli, K Lafferty and N Martinez for helpful discussions. E.L.S. is supported by the NSF GRFP. M.J.M.-S. is supported by the U.S. Department of Education grant P200A150101. S.A. is supported by NSF DEB-1148867. This work was inspired by the Parasites and Food Webs Working Group supported by the National Center for Ecological Analysis and Synthesis, a Center funded by NSF (DEB-0553768), the University of California, Santa Barbara and the State of California.

Publisher Copyright:
© 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society

Copyright 2018 Elsevier B.V., All rights reserved.


  • community structure
  • degree
  • likelihood
  • motifs
  • species role
  • stochastic blockmodel

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