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Ecological Meltdown in Predator-Free Forest Fragments
John Terborgh,1*Lawrence Lopez,2Percy Nuñez,3Madhu Rao,45Ghazala Shahabuddin,6Gabriela Orihuela,7Mailen Riveros,8Rafael Ascanio,9Greg H. Adler,11Thomas D. Lambert,10Luis Balbas12
The manner in which terrestrial ecosystems are regulated is
controversial. The "top-down" school holds that predators limitherbivores and thereby prevent them from overexploiting vegetation."Bottom-up" proponents stress the role of plant chemical defensesin limiting plant depredation by herbivores. A set of predator-freeislands created by a hydroelectric impoundment in Venezuela allowsa
test of these competing world views. Limited area restrictsthe fauna
of small (0.25 to 0.9 hectare) islands to predatorsof invertebrates
(birds, lizards, anurans, and spiders), seedpredators (rodents), and
herbivores (howler monkeys, iguanas,and leaf-cutter ants). Predators
of vertebrates are absent, anddensities of rodents, howler monkeys,
iguanas, and leaf-cutterants are 10 to 100 times greater than on the
nearby mainland,suggesting that predators normally limit their
populations. Thedensities of seedlings and saplings of canopy trees
are severelyreduced on herbivore-affected islands, providing evidence
of atrophic cascade unleashed in the absence of top-down regulation.
1 Center for Tropical Conservation, Duke
University, Box 90381, Durham, NC 27708, USA.
2 Department of Biological Sciences, Florida
International University, Miami, FL 33199, USA.
3 Herbario Vargas, Universidad Nacional "San
Antonio de Abad" de Cusco, Cusco, Peru.
4 Wildlife
Conservation Society, 2300 South Boulevard, Bronx, New York, NY 10464, USA.
5 Conservation Biology Group, Department of
Zoology, Downing Street, Cambridge University, Cambridge CB2 3EJ, UK.
6 Chintan Environmental Research and Action Group,
238 Siddhartha Enclave, New Delhi 110014, India.
7 Universidad Ricardo Palma, Facultad de Ciencias
Biológicas, Jose Gonzales 684, Lima 18, Peru.
8 Fundación Museo de Ciencias/Centro Adolfo
Ernst, Apartado Postal 5883, Caracas 1010, Venezuela.
9 Universidad Complutense de Madrid, Departamento de
Ecología, Facultad de Ciencias Biológicas, Ciudad
Universitaria, 28040 Madrid, Spain.
10 Faculty of
Forestry, University of Toronto, Ontario M5S 3B2, Canada.
11 Department of Biology and Microbiology,
University of Wisconsin Oshkosh, 800 Algoma Boulevard, Oshkosh, WI
54901-8640, USA.
12 EDELCA, Apartado 28, Puerto
Ordaz, Estado Bolívar, Venezuela.
*
To whom correspondence should be addressed: E-mail:
manu{at}duke.edu
The editors suggest the following Related Resources on Science sites:
In Science Magazine
LETTERS
Gustavo A. B. da Fonseca, Claude Gascon, Marc K. Steininger, Thomas Brooks, Russell A. Mittermeier, and Thomas E. Lacher Jr. (8 March 2002) Science295 (5561), 1835b.
[DOI: 10.1126/science.295.5561.1835b] |Full Text »
PERSPECTIVES
Jared Diamond (30 November 2001) Science294 (5548), 1847.
[DOI: 10.1126/science.1067012] |Summary »|Full Text »|PDF »
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