Biology Reference
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3 .
Interspecif ic competition:
definition and effects on species
Interspecific competition is central to the equilibrium versus nonequili-
brium debate. It is intuitively likely that under equilibrium conditions and
in saturated niche space, competition will be more common and more
intense than under nonequilibrium conditions and in nonsaturated niche
space. In this chapter, I discuss evidence for and against the occurrence
and significance of interspecific competition. The discussion begins with
a definition of competition and its different types, and the main cause
thought to be responsible for its occurrence, i.e., resource limitation.
A discussion on the effects of competition on species in this chapter is
followed by one on effects in communities in Chapter 4 . The final section
in Chapter 4 deals with general aspects and gives a conclusion.
Definition and types of competition, resource
limitation as its main cause
Definition and types of competition
Interspecific competition results in the increase of the population density
of one species at the expense of the reproductive rate and population
density of another (Crawley 1986 ). However, it is not species but indi-
viduals within species that interact, and therefore, competition (at least as
a starting point, but see p. 50) is better defined as an interaction between
individuals that arises because of shared requirements for a limiting
resource. It leads to reduced survival, growth and/or reproduction of at
least some of the individuals (Begon et al. 1996 ).
Competition may be between individuals of the same species, i.e., it
is intraspecific, or it may be between individuals of different species,
i.e., interspecific. Competition may either be via exploitation of resources
or by active interference (Park 1954 ). In exploitation competition, com-
peting individuals use the same limited resource. In interference compe-
tition, some kind of activity may directly or indirectly reduce the access of
 
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