The Theory of Island Biogeography is a 1967 book by the ecologist Robert MacArthur and the biologist Edward O.

[1] The book popularized the theory that insular biota maintain a dynamic equilibrium between immigration and extinction rates.

MacArthur synthesized Wilson's ideas about competition, colonization and equilibrium into a simple graphical representation of immigration and extinction curves, from which one can determine the equilibrial species number on an island.

In Chapters 2 and 3, MacArthur and Wilson postulate that insular species richness depends on island size and isolation from source regions.

The authors surmise that pioneering species can be excluded for the following reasons: the island has saturated levels of pre-existing competition, the pioneering species cannot maintain a population large enough to avoid extinction, and the island hosts too many or too few natural predators.

In this period, abilities for dispersal are commonly reduced, and colonizers will either differentiate or assimilate with competing species.

The insular biota equilibrium theory was experimentally tested by E. O. Wilson and his then-graduate student Daniel Simberloff in six small mangrove islands in the Florida Keys.

[1] In 2007, a symposium was held at Harvard University honoring the fortieth anniversary of The Theory of Island Biogeography.

[3] Following this conference, a collection of papers was published in the book The Theory of Island Biogeography Revisited.