The Compartmentation of Real and Assembled Ecosystems

The dominant cliques of graph theory provide an unambiguous compartmentation for ecosystems. It is suggested here that it might make ecological sense to regard dominant cliques as something like "trophic guilds." The dominant clique structure of 40 real food webs collected from the published literature by Briand (1982) is investigated. It is found that food webs from environments classifiedd by Briand as "fluctuating" differ significantly, both in number and in average size of dominant cliques, from food webs from environments classified by Briand as "constant." In addition, food web intervality (Cohen 1978) is found to be associated with poverty in dominant cliques. Adding constraints on dominant clique number to "assembled" food web models (Yodzis 1981) yields mathematical food web universes which predict the observed frequency of interval food webs.