An orb-weaver spider exploits an ant–acacia mutualism for enemy-free space
Article first published online: 2 JAN 2014
© 2013 The Author. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 4, Issue 3, pages 276–283, February 2014
How to Cite
Ecology and Evolution 2014; 4(3):276–283
- Issue published online: 4 FEB 2014
- Article first published online: 2 JAN 2014
- Manuscript Accepted: 1 DEC 2013
- Manuscript Revised: 27 NOV 2013
- Manuscript Received: 7 NOV 2013
- Thomas F. Jeffress and Kate Miller Jeffress Memorial Trust
- Virginia Foundation for Independent Colleges
- Lynchburg College
- Acacia ant;
- enemy-free space;
- orb-weaver spider;
Exploiters of protection mutualisms are assumed to represent an important threat for the stability of those mutualisms, but empirical evidence for the commonness or relevance of exploiters is limited. Here, I describe results from a manipulative study showing that an orb-weaver spider, Eustala oblonga, inhabits an ant-acacia for protection from predators. This spider is unique in the orb-weaver family in that it associates closely with both a specific host plant and ants. I tested the protective effect of acacia ants on E. oblonga by comparing spider abundance over time on acacias with ants and on acacias from which entire ant colonies were experimentally removed. Both juvenile and adult spider abundance significantly decreased over time on acacias without ants. Concomitantly, the combined abundance of potential spider predators increased over time on acacias without ants. These results suggest that ant protection of the ant-acacia Acacia melanocerus also protects the spiders, thus supporting the hypothesis that E. oblonga exploits the ant–acacia mutualism for enemy-free space. Although E. oblonga takes advantage of the protection services of ants, it likely exacts little to no cost and should not threaten the stability of the ant–acacia mutualism. Indeed, the potential threat of exploiter species to protection mutualisms in general may be limited to species that exploit the material rewards traded in such mutualisms rather than the protection services.