The Ecology Book

62

A

keystone species plays

a crucial role in the way

an ecosystem functions,

even though it is often a small

part of the overall biomass of the

ecosystem. Because it exerts a

disproportionately large effect on

the environment relative to its

biomass, if a keystone species

disappears from an ecosystem,

that ecosystem will change

dramatically. The importance of

keystone species was brought to

light by the American biologist

Robert Paine—who derived the

term from the central “keystone” at

the top of an arch that stops it from

collapsing—in his 1969 article “A

Note on Trophic Complexity and

Community Stability.”

The keystone concept

In the 1960s, Paine spent several

years studying the animals of the

intertidal zone of Tatoosh Island

on the Pacific coast of Washington

State. He removed the ocher

starfish and watched its key prey,

a mussel whose numbers had

been kept in check by the starfish,

dominate the zone, replacing other

subordinate species. The removal

of a single, keystone species had a

clear impact on many others. Paine

developed the idea to include the

concept of “trophic cascades”—the

strong, top-down effects that ripple

through an ecosystem and its

organisms. Since Paine’s work

with starfish, several studies

have demonstrated that there are

KEYSTONE SPECIES

Black-tailed prairie dogs look

out from their burrow in a field in

Wyoming. Study of this species has

revealed its key role in fostering

diversity in its native habitat.

IN CONTEXT

KEY FIGURE

Robert Paine (1933–2016)

BEFORE

1950s In Kenya, farmer and

conservationist David

Sheldrick introduces elephants

to Tsavo East National Park,

and discovers this results in a

major increase in biodiversity.

1961 Fieldwork by American

ecologist Joseph Connell on

Scotland’s rocky shores shows

that removing predatory

whelks alters the distribution

of their barnacle prey.

AFTER

1994 In the US, a group of

ecologists led by Brian Miller

publishes a paper explaining

the valuable role prairie dogs

play as a keystone species.

2016 Fieldwork leads marine

ecologist Sarah Gravem to

conclude that organisms can

be keystone species in some

places but not in others.

Do you want an auto

mechanic who...can name,

list, and count all of the parts

of your engine, or one who

really understands how each

part interacts with the others

to make a working engine?

Robert Paine

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