Biology Reference
In-Depth Information
4
.
Interspecific competition: effects
in communities and conclusion
The
previous chapter
dealt with the effects of competition on species.
Here we examine effects in communities, although it should be noted
that there is some overlap: effects on species and communities cannot
always be clearly distinguished.
Isolationist (individualistic, non-interactive) and interactive
communities
Wiens (
1984
) distinguished interactive communities (structured by inter-
active processes, mainly competition), and non-interactive communities
(communities largely ''structured'' by individualistic responses of species).
He points out that most studies deal with interactive systems. Holmes and
Price (
1986
) applied this distinction to parasite communities, distinguish-
ing interactive and isolationist (non-interactive) infracommunities of
parasites. In the former, colonization probabilities of hosts are high, and
communities are likely to be saturated and equilibrial. In isolationist
communities, probabilities of colonization are low, resulting in unsat-
urated, nonequilibrial communities. Holmes and Price, in their synthesis,
conclude that distinguishing between isolationist and interactive com-
munities is ''probably too crude to be of lasting utility.''
In the following section, I give some examples of interactive commu-
nities with evidence for interspecific competition, and of isolationist
communities without such evidence.
Examples of competition in communities
Although evidence in many cases is poor, it seems nevertheless that
competition is of some importance in many communities (for parasites
see some contributions in Esch et al.
1990
, and Lello et al.
2004
).
Schoener (
1983
) reviewed evidence for interspecific competition in
the past literature: in 90% of the studies and 76% of the species, some
