ABSTRACT
Few subjects have evoked as much interest and controversy as competition. In all habitats there is a finite amount of food or space, and as populations increase in density, competition for these resources may occur. Whether this competition assumes a dominant rôle in structuring communities and in moulding the evolution of the species is much debated. Although competition has long been invoked as just such a dominant force, the drawing together of theory, observation and experiment into what is referred to as “competition theory” owes much of its roots to Hutchinson’s seminal paper, published in 1959. In posing the question “Why are there so many species?”, Hutchinson put forward five major themes, one of which addresses the question of how similar co-existing species with overlapping requirements can be, if co-existence is to continue. This has formed the focal point of much competition theory, leading to attempts to quantify overlap between species and competitive impact of one species on another-factors that are difficult to assess in real-world situations. In its extreme form this approach has led to a preoccupation with niche differences as a means of allowing presumed competitors to co-exist. Hutchinson himself would, I am sure, be dismayed by the uncritical acceptance and application of his idea. Too often competition is assumed to exist, and differences between species (and there must be differences if one searches hard enough) are assumed to allow ‘apportionment’ of the habitat and to permit continued co-existence. These assumptions are testable but all too often are untested before they are applied to explain ecological phenomena.
