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


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


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

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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