Species Abundance: Natural Regulation of Insular Variation.

Variation in numbers of land plant species on islands in the Galapagos Archipelago can be predicted on the basis of elevation, area of the adjacent island, distance from the nearest island, and distance from the center of the archipelago, but not on the basis of the area of the host island. Multiple linear regression (y = bx(1) + bx(2) . . .) gives better "goodness of fit" than curvilinear analysis (y = bx(z)). The variation in number of species on large islands can be predicted more accurately than the variation on small ones. Ecologic diversity and isolation are the natural regulators of species abundance.