Experimental Insular Zoogeography: Some Tests of the Equilibrium Theory Using Meiobenthic Harpacticoid Copepods

Few tests of the predictions of the equilibrium theory of island biogeography have been conducted and reported in the extensive literature on the subject. The second of a pair of experiments specifically designed to test the major predictions of the theory, making use of an intertidal community of meiobenthic harpacticoid copepods, is described. The results obtained were consistent with the equilibrium theory: the more isolated an experimentally created island, the fewer the number of species to be found there, and the lower the species diversity. The decrease in species richness was inferred to result from a lower inmigration rate. The processes of immigration and extinction were described as by the equilibrium theory: as the species richness of a newly colonized island increased, so the extinction rate increased and the immigration rate decreased. However, no equilibrium was attained, because of the seasonal increase in the species richness of the beach copepod community, the source region of the insular faunas. Evidence is presented that the systems were tending towards an equilibrium, in that the ratio of the rate of immigration to that of extinction was tending towards anity. Such considerations are discussed with respect to the persistence of species populations in the intertidal zone.