The Ecology Book

52

COMPLETE

COMPETITORS

CANNOT COEXIST

COMPETITIVE EXCLUSION PRINCIPLE

C

ompetition is the driver of

evolution; the need to be

bigger, stronger, and better

inevitably leads to adaptations that

give a species an edge. When two

species compete for identical

resources, the one which has any

advantage will outdo the other. As

a result, the weaker of the two

species either becomes extinct or

adapts, so that it no longer

competes. This proposition, known

as the “competitive exclusion

principle,” was set out by Russian

microbiologist Georgy Gause and

is also known as Gause’s Law.

Gause devised his principle

from laboratory experiments, using

cultures of microorganisms, rather

than from observations in nature. In

IN CONTEXT

KEY FIGURE

Georgy Gause (1910 –86)

BEFORE

1925 Alfred James Lotka first

uses equations to analyze

variations in predator–prey

populations, as does

mathematician Vito Volterra,

independently, a year later.

1927 Volterra enlarges and

updates his 1926 study to

include various ecological

interactions within

communities.

AFTER

1959 G. Evelyn Hutchinson

extends Gause’s ideas and

produces a ratio describing the

limit of similarity between two

competing species.

1967 Robert MacArthur and

Richard Levins use probability

theory and Lotka–Volterra

equations to describe how

coexisting species interact.

How warblers coexist

Five species of

warblers are able to

share the same tree,

because each inhabits

its own “niche.” Living

in this way, without

much overlap, the

birds do not compete.

Bay-breasted

Warbler

Cape May

Warbler

Blackburnian

Warbler

Black-throated

Green Warbler

Yellow-rumped

Warbler

US_052-053_Competitive_Exclusion_Principal.indd 52 12/11/18 6:24 PM