VARIATION IN SPECIES RICHNESS - TOWARDS A UNIFICATION OF HYPOTHESES

The question, ''why do areas vary in species richness?'' has been impo rtant throughout the history of ecology. It is difficult to answer def initively because we have so many (at least 120) plausible hypotheses. This abundance of hypotheses has led to a number of attempts to class ify them. Unfortunately, richness hypotheses often defy such categoriz ation. Instead of placing species richness hypotheses into categories, I suggest an alternative approach: to treat species richness hypothes es as violations of the assumptions of Gause's Competitive Exclusion P rinciple. This is a very similar approach to the pedagogy of populatio n genetics: evolution occurs if and only if at least one assumption of the Hardy-Weinberg principle is violated. The classification of hypot heses advocated here treats interspecific competition as a central org anizing concept in community theory. However, it does not treat compet ition as an organizing concept in communities: indeed, the relaxation or disruption of competition is considered to be the status quo in the majority of communities.