Island biogeography of vertebrates in Georgian Bay Islands National Park

Abstract

Terrestrial vertebrates on 28 of 77 islands in Georgian Bay Islands National Park were examined by taxon (i.e., nonvolant mammals, herptiles, and birds) to determine whether the number of species on each island was affected by variation in dispersal capability and susceptibility to extinction, as predicted by the equilibrium theory of island biogeography. About 70% of the variation in number of species on islands was accounted for by the area of the islands. Species (S) – area (A) relationships (S = cAz) for birds, herptiles, and nonvolant mammals all differed significantly in slope and intercept (P < 0.05). Intertaxa comparisons revealed that birds exhibited the greatest numbers of species on all sizes of islands and smallest slope (z = 0.32); herptiles exhibited intermediate numbers of species on all sizes of islands and intermediate slope (z = 0.37). Of all taxa, nonvolant mammals exhibited the lowest numbers of species on all sizes of islands and greatest slope (z = 0.42), consistent with the predictions of the theory. These results reinforce earlier suggestions that designs for nature reserves should accommodate intertaxa variation in dispersal ability and susceptibility to extinction.