Publication Date:
2001-12-01
Description:
The manner in which terrestrial ecosystems are regulated is controversial. The "top-down" school holds that predators limit herbivores and thereby prevent them from overexploiting vegetation. "Bottom-up" proponents stress the role of plant chemical defenses in limiting plant depredation by herbivores. A set of predator-free islands created by a hydroelectric impoundment in Venezuela allows a test of these competing world views. Limited area restricts the fauna of small (0.25 to 0.9 hectare) islands to predators of invertebrates (birds, lizards, anurans, and spiders), seed predators (rodents), and herbivores (howler monkeys, iguanas, and leaf-cutter ants). Predators of vertebrates are absent, and densities of rodents, howler monkeys, iguanas, and leaf-cutter ants are 10 to 100 times greater than on the nearby mainland, suggesting that predators normally limit their populations. The densities of seedlings and saplings of canopy trees are severely reduced on herbivore-affected islands, providing evidence of a trophic cascade unleashed in the absence of top-down regulation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Terborgh, J -- Lopez, L -- Nunez, P -- Rao, M -- Shahabuddin, G -- Orihuela, G -- Riveros, M -- Ascanio, R -- Adler, G H -- Lambert, T D -- Balbas, L -- New York, N.Y. -- Science. 2001 Nov 30;294(5548):1923-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Tropical Conservation, Duke University, Box 90381, Durham, NC 27708, USA. manu@duke.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11729317" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Ants/physiology
;
Anura/physiology
;
Birds/physiology
;
*Ecosystem
;
Female
;
*Food Chain
;
Fresh Water
;
*Geography
;
Haplorhini/physiology
;
Iguanas/physiology
;
Lizards/physiology
;
*Models, Biological
;
Population Density
;
Power Plants
;
Reproduction
;
Rodentia/physiology
;
Spiders/physiology
;
Swine/physiology
;
Trees/*physiology
;
Venezuela
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
