Readings Seminar
11 Sept 2003
Paine (1966)
LAJ
Robert T. Paine Biography:
Department of Zoology, University of Washington, Seattle, Washington
Marine, coastal, intertidal ecosystems
Marine benthic invertebrates
Food webs, trophic levels
First(?) to introduce concept of keystone species (1969)
Summary in Foundations p723
Sample of additional works:
- 1969. A note on trophic complexity and community stability. American Naturalist 103: 91-93.
- 1974. Intertidal community structure: Experimental studies on the relationship between a dominant
competitor and its principal predator. Oecologia 15: 93-120.
- 1980. Food webs, linkage interaction strength, and community infrastructure. Journal of Animal
Ecology 49: 667-685.
Paine, RT (1966) Food web complexity and species diversity. American Naturalist v100
n910: 65 – 75.
Main points – To explore latitudinal diversity gradient, and effect of predation on diversity.
Hypothesis: Local species diversity is directly related to the efficiency with which predators prevent the
monopolization of the major environmental requisites by one species.”
i.e. If primary consumers compete for space, then the presence of a predator will prevent one species from
dominating the space.
Evidence cited (i.e. Connell 1961):
- Predation and/or parasitism is capable of preventing extinction in competitive situations (barnacles).
- Predator removal has lead to local extinctions (benthic invertebrates and algae)
Extension of hypothesis: The proportion of predatory species is known to be relatively larger in certain
diverse situations. (ratio of carnivores to all species)
-
Studied food webs of marine systems
Compared temperate (Washington state), subtropical (California), tropical (Costa Rica)
Food acquisition based on number of prey items consumed and “caloric equivalent” based on prey
size
Comparison of study sites:
- Temperate: Top predator feeding on five prey species, one intermediate predator feeding on two of
the five prey species; ratio of carnivores = 0.18
- Subtropical: More complex – two intermediate levels of predators under top predator; coexist by
relying on higher proportion of certain prey items; ratio of carnivores = 0.24
- Tropical: simple system, no intermediate predator present; no ratio of carnivores given
Differences in diversity explained by differences in seasonal variation in temperature: wider fluctuations
in seasonal temperature result in higher levels of diversity.
Also suggested are topographical heterogeneity, organic enrichment (though there is also evidence of
decreasing diversity with increasing enrichment), and rate and stability of primary production (occurring
throughout the seasons rather than in a single bloom).
Removal experiment at Washington site: Removal of top predator resulted in growth and replacement of
species in turn, ultimately resulting in a decrease in diversity. (Succession leading to simplification rather
than complexity.)