Ecological applications of niche theory - Ecological Applications: Toward a Sustainable World - page 38

consumed has a critical consequence for the way that organisms interact with each other. By con-
suming resources, individuals may reduce resource availability to others of their own or different
species. Intraspecifi c competition for a limited resource occurs among individuals of a single
species; its counterpart, involving competition among individuals of different species, is interspe-
cifi c competition. The ultimate effect of competition is on the survival, growth and reproduction
of the competitors. In extreme cases, interspecifi c competition can lead to the extinction of one of
the competing species or its restriction to a more limited set of circumstances.

The fundamental niche - an idea with many dimensions
Where an organism lives is its habitat. Its fundamental niche, on the other hand, is not a place but
an idea - a summary of the organism's tolerances and requirements, within which the species can
maintain a population in the long term (and without the need for inward migration of individuals).
The modern concept has its roots in Hutchinson's (1957) proposal that the niche defi nes the condi-
tions and resources needed by a species to practice its way of life. Temperature, for instance, limits
the growth and reproduction of all organisms, but organisms of different species tolerate different
ranges of temperature - this range is one dimension of an organism's ecological niche. Figure 2.1a
shows how some species of plants vary in this niche dimension - specifi cally, how they vary in the
range of temperatures at which they can successfully photosynthesize. Of course, there are many

(a) Temperature ( ° C) (b)

5 0 5 0 5 0

Ranunculus glacialis 2600

100% mortality
50% mortality

Oxyria digyna 2500

Geum reptans 2500

Pinus cembra 1900

25

Picea abies 1900

Betula pendula 1900

Larix decidua 1900

Picea abies 900

20

Larix decidua 900

Zero
mortality

Leucojum vernum 600

Betula pendula 600

Fagus sylvatica 600 15

Taxus baccata 550

Abies alba 530

Prunus laurocerasus 250

10

Quercus ilex 240

Olea europaea 240

Quercus pubescens 240

Citrus limonun 80

(m)

5 05 015

20 25 30 35 40 45

Salinity (%)

(c)

Temperature

Fig. 2.1 (a) A niche in one dimension. The range of temperatures at which a variety of plant
species from the European Alps can achieve net photosynthesis at low intensities of radiation
(70 W m −2 ). (After Pisek et al., 1973.) (b) A niche in two dimensions for the sand shrimp
( Crangon septemspinosa ) showing the fate of egg-bearing females in aerated water at a range
of temperatures and salinities. (After Haefner, 1970.) (c) A diagrammatic niche in three
dimensions for an aquatic organism showing a volume defi ned by temperature, pH and
availability of food. (After Townsend, et al., 2003.)