The Ecology Book

63

many other keystone organisms,

and they each fulfill their role in

different ways.

Ecological engineers

Prairie dogs in the American

Midwest are a good example of a

keystone species whose impact is

the result of their “engineering”

activities. Huge colonies of these

small mammals dig networks of

tunnels beneath the prairie

grasslands. They sleep and raise

their young in these extensive

burrows, converting the grassland

into a suitable habitat.

The prairie dogs’ constant

digging dramatically increases

soil turnover and allows nutrients

and water from rain and snow to

penetrate deeper than would

otherwise be the case. The damp,

nutrient-rich soil encourages a

diversity of plants, and birds such

as Mountain Plovers feed and nest

in the short grass. Predators like

Ferruginous Hawks and black-

footed ferrets are attracted to the

area to hunt for prey, and the ferrets

and tiger salamanders use the

burrows for shelter. Almost 150

species of plant and animal are

known to benefit from prairie dog

colonies. Although there are

“losers”—notably vertebrates that

favor tall vegetation—the prairie

dogs’ presence increases overall

biodiversity. When colonies die out,

scrubby patches of mesquite

vegetation replace short grasses,

plovers abandon the area, and

predator numbers decline.

Coral cleaners

The princess parrotfish in the

Caribbean is another keystone

species, this time because of the

consequences of its feeding. The

fish lives around coral reefs, where

corals fight each other for light,

nutrients, and space. The parrotfish

scrapes the surfaces of the corals to

remove layers of algal seaweed to

eat. If the parrotfish did not do this,

clumps of seaweed would grow on

the corals, smothering as well as ❯❯

See also: Predator–prey equations 44–49 ■ Mutualisms 56–59 ■ Animal ecology

106–113 ■ Trophic cascades 140–143 ■ Evolutionarily stable state 154–155

ECOLOGICAL PROCESSES

Robert Paine

Born in 1933, in Cambridge,

Massachusetts, Robert Paine

studied at Harvard. After a

stint in the US Army, where

he was the battalion gardener,

Paine focused his research

on marine invertebrates.

His study of the relationship

between starfish and mussels

on the Paciic coast led him

to propose the concept

of keystone species—the

disproportionate impact that

a single species can have on

its ecosystem.

Paine worked for most of

his career at the University

of Washington, where he

popularized field manipulation

experiments, or “kick-it-and-

see” ecology. He was awarded

the International Cosmos

Award by the National

Academy of Sciences in 2013,

and died in 2016.

Key works

1966 “Food Web Complexity

and Species D iversity,”

American Naturalist

1969 “A Note on Trophic

Complexity and Community

Sta bi l ity,” American Naturalist

1994 Marine Rocky Shores

and Community Ecology: An

Experimentalist’s Perspective

Whelks feed on

barnacles; they

are predators.

In areas where

there are large

concentrations

of barnacles, groups of

whelks congregate—

like wolf packs.

They also display

aggression toward

their prey.

Whelks are like

little wolves in

slow motion.

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