Essay on the Theory of “Island Biogeography”
Islands have fascinated biologists, geographers, and ecologists since Charles Darwin visited the Galapagos Island. Landscape patches on mainland likely function as islands within landscape mosaic.
For example, Andes Mountains of Ecuador stirred the imagination of Alexander von Humboldt (11769-1859), who laid foundations of mountain genecology there. These Andean landscapes, cradle of Humboldt’s work should be considered as birthplace of ecology, especially holistic ecology (Sachs, 1995).
The peaks of such mountains especially at approximately same elevations, functions as terrestrial islands regarding plant and animal community types. J. H. Brown (1971, 1978) investigated insular biography of these “islands” in regard to small mammal and bird population diversity and abundances.
These patches, which vary in size and distance, fit the theory of island biogeography as proposed by MacArthur and Wilson (1963). For example, a patch of forest may be located in a “Sea” of agricultural cropland isolated from other patches in the landscapes. Effect of patch size and isolation appears to have a pronounced influence on nature and diversity of species within these landscape patches.
Theory of island biogeography states that number of species of a given taxon (insect, birds, or mammals) present on an island or within a patch represents a dynamic equilibrium between rate of immigration of new colonizing species of that taxon and rate of extinction of previously established species.