Species-Energy Theory: An Extension of Species-Area Theory

Abstract

A more general biogeographic theory of island species number is produced by replacing area with a more direct measure of available energy in the models of MacArthur and Wilson and Preston. This theory, species-energy theory, extends beyond species-area theory in that it applies to islands that differ in their per-unit-area productivity due to differences in physical environment, such as climate. Examination of data on species number of angiosperms and of land and freshwater birds on islands worldwide, ranging from Greenland and Spitsbergen to New Guinea and Jamaica, demonstrates that species-energy theory can explain 70 to 80% of the variation in species number on such widely varying islands, and further suggests the existence of regular geographic trends in resource utilization or species-abundance patterns. The concepts embodied in species-energy theory can in principle be used to develop predictions of species’ abundances and probabilities of occurrence on an island. Species-energy theory may also provide a unified basis for understanding a broad set of observations of patterns in species diversity.