MacArthur and Wilson (1963, 1967) first published theory of island biogeography. This theory holds that number of species on an island is determined by equilibrium between immigration of new species and extinction of those species already present.
As rates of immigration and extinction depend on size of islands and their distance from mainland, a general equilibrium can be predicted. Four equilibrium points are shown, representing a small, distant island predicted to have few species, S1 a small, nearby or a larger, distant island, predicted to be intermediate in term of species richness S2, and a large, nearby island that should support many species, S3.
This model demonstrates interplay of isolation, natural selection, dispersal, extinction and speciation that has attracted attention of population ecologists and evolutionary biologists to island biogeography for more than a century. This model is of fundamental importance in landscape ecology and conservation biology.
Image Source: 2.bp.blogspot.comPI/s1600/giving_talks.jpg
ADVERTISEMENTS:
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.
ADVERTISEMENTS:
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.