8
RICHARD 5. MILLER
consumers as a single set of interactions, but this need not disguise the
fact that an array of distinctive phenomena, each with unique ecological
and evolutionary properties, has produced the observed results.
Birch (1957) has reviewed several cases in which various authors
have described interactions such as predation and parasitism as forms
of competition (cf. Nicholson, 1933), regardless of the fact that the
species interaction did not involve a common resource. Thus, Nicholson
(1937) states that “. . . competition for food and space, and the interaction of natural enemies and their hosts, can both be represented by
the same fundamental formula and its corresponding exponential
curve. . .” so that the criterion of competition is merely that survival
decreases as density increases. There is a substantial body of literature
and theory pertaining strictly to interactions between members of the
same species or between species at the same trophic level, in which the
interaction is directed toward a resource which is a common requirement
for both members of the interaction. There is no conceptual problem in
delineating the phenomenon of competition in these terms, nor is there
any obvious theoretical advantage in considering competition to be
more than an ecologically qualified “contest between two rivals for a
common object.”
B. COMPONENT ELEMENTS O F COMPETITION
Elton and Miller (1954), Park (1954) and others distinguish between
interference and exploitation as component elements of the competition
process. While the general consequences of a competitive interaction
may be the same in either case (e.g. elimination of one species from a
niche), the process leading to this result may involve one or both of
these elements.
“Interference” refers to any activity which either directly or indirectly
limits a competitor’s access to a necessary resource or requirement. It
usually operates in a spatial context, as in the case of territoriality, and
assures possession of some minimum requirement by one individual or
species. It may involve a structural resource such as a nest site or song
post, or it may be a space containing a requisite amount of food or
nutrients. The term “interference” has been used in somewhat different
ways. It is broadly synonymous with the term “contest” as used by
Nicholson (19!55), in that a contest in this sense invariably involves
interference. Brian (1956) refers to interference and exploitation as
“isolated components of the dual competition concept” and concludes
that the Lotka-Volterra model involves competition by interference
alone while the Windsor (1934) model involves only exploitation. An
objection to the Lotka-Volterra model put forth by Andrewartha and
RICHARD 5. MILLER
consumers as a single set of interactions, but this need not disguise the
fact that an array of distinctive phenomena, each with unique ecological
and evolutionary properties, has produced the observed results.
Birch (1957) has reviewed several cases in which various authors
have described interactions such as predation and parasitism as forms
of competition (cf. Nicholson, 1933), regardless of the fact that the
species interaction did not involve a common resource. Thus, Nicholson
(1937) states that “. . . competition for food and space, and the interaction of natural enemies and their hosts, can both be represented by
the same fundamental formula and its corresponding exponential
curve. . .” so that the criterion of competition is merely that survival
decreases as density increases. There is a substantial body of literature
and theory pertaining strictly to interactions between members of the
same species or between species at the same trophic level, in which the
interaction is directed toward a resource which is a common requirement
for both members of the interaction. There is no conceptual problem in
delineating the phenomenon of competition in these terms, nor is there
any obvious theoretical advantage in considering competition to be
more than an ecologically qualified “contest between two rivals for a
common object.”
B. COMPONENT ELEMENTS O F COMPETITION
Elton and Miller (1954), Park (1954) and others distinguish between
interference and exploitation as component elements of the competition
process. While the general consequences of a competitive interaction
may be the same in either case (e.g. elimination of one species from a
niche), the process leading to this result may involve one or both of
these elements.
“Interference” refers to any activity which either directly or indirectly
limits a competitor’s access to a necessary resource or requirement. It
usually operates in a spatial context, as in the case of territoriality, and
assures possession of some minimum requirement by one individual or
species. It may involve a structural resource such as a nest site or song
post, or it may be a space containing a requisite amount of food or
nutrients. The term “interference” has been used in somewhat different
ways. It is broadly synonymous with the term “contest” as used by
Nicholson (19!55), in that a contest in this sense invariably involves
interference. Brian (1956) refers to interference and exploitation as
“isolated components of the dual competition concept” and concludes
that the Lotka-Volterra model involves competition by interference
alone while the Windsor (1934) model involves only exploitation. An
objection to the Lotka-Volterra model put forth by Andrewartha and