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Science 11 January 2008:
Vol. 319. no. 5860, pp. 192 - 195
DOI: 10.1126/science.1151579
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Reports

Breakdown of an Ant-Plant Mutualism Follows the Loss of Large Herbivores from an African Savanna

Todd M. Palmer,1,2,4* Maureen L. Stanton,2,3,4 Truman P. Young,2,4,5 Jacob R. Goheen,1,4,6 Robert M. Pringle,4,7 Richard Karban8

Mutualisms are key components of biodiversity and ecosystem function, yet the forces maintaining them are poorly understood. We investigated the effects of removing large mammals on an ant-Acacia mutualism in an African savanna. Ten years of large-herbivore exclusion reduced the nectar and housing provided by plants to ants, increasing antagonistic behavior by a mutualistic ant associate and shifting competitive dominance within the plant-ant community from this nectar-dependent mutualist to an antagonistic species that does not depend on plant rewards. Trees occupied by this antagonist suffered increased attack by stem-boring beetles, grew more slowly, and experienced doubled mortality relative to trees occupied by the mutualistic ant. These results show that large mammals maintain cooperation within a widespread symbiosis and suggest complex cascading effects of megafaunal extinction.

1 Department of Zoology, University of Florida, Gainesville, FL 32611, USA.
2 Center for Population Biology, University of California, Davis, CA 95616, USA.
3 Section of Evolution and Ecology, University of California, Davis, CA 95616, USA.
4 Mpala Research Centre, Box 555, Nanyuki, Kenya.
5 Department of Plant Environmental Sciences, University of California, Davis, CA 95616, USA.
6 Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
7 Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
8 Department of Entomology, University of California, Davis, CA 95616, USA.

* To whom correspondence should be addressed. E-mail: tmpalmer{at}zoo.ufl.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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E-Letters:

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Nature's Vast Mesher
Eugene Blank
Science Online, 6 Mar 2008 [Full text]

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