Community Ecology

, Volume 4, Issue 1, pp 79–88 | Cite as

Quantifying the importance of species and their interactions in a host-parasitoid community

  • F. JordánEmail author
  • W. -C. Liu
  • F. J. F. van Veen


We present a new method to asses the strength of indirect interactions and to indentify candidate keystone species in quantitative food webs. We apply this method to the structural analysis of a host-parasitoid community. The strength and symmetry of indirect interactions between 12 leaf-miner hosts and their 27 hymenopteran parasitoids are quantified. It is shown that (1) quantifying longer pathways helps in determining which species have more important direct or indirect effects on others, (2) a keystone pattern of relative species importance, based on positionality in the interaction network, seems to characterize this community, (3) considering longer pathways results in a characteristic ‘few strong - many weak’ distribution of interaction strength, and (4) between the majority of species pairs the interaction is weakly asymmetrical. We emphasise that a very simple network algebra approach may offer important predictions on both species- and community-level patterns.


Host-parasitoid community Indirect effects Interaction strength Interaction symmetry Keystone species Network algebra Phyllonorycter 


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© Akadémiai Kiadó, Budapest 2003

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  1. 1.Department of Plant Taxonomy and EcologyEötvös Loránd UniversityBudapestHungary
  2. 2.NERC Centre for Population BiologyImperial College at Silwood ParkAscot, BerkshireUK

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