Island biogeography

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Island biogeography

The distribution of plants and animals on islands. Islands harbor the greatest number of endemic species. The relative isolation of many islands has allowed populations to evolve in the absence of competitors and predators, leading to the evolution of unique species that can differ dramatically from their mainland ancestors.

Plant species produce seeds, spores, and fruits that are carried by wind or water currents, or by the feet, feathers, and digestive tracts of birds and other animals. The dispersal of animal species is more improbable, but animals can also be carried long distances by wind and water currents, or rafted on vegetation and oceanic debris. Long-distance dispersal acts as a selective filter that determines the initial composition of an island community. Many species of continental origin may never reach islands unless humans accidentally or deliberately introduce them. Consequently, although islands harbor the greatest number of unique species, the density of species on islands (number of species per area) is typically lower than the density of species in mainland areas of comparable habitat. See Population dispersal

Once a species reaches an island and establishes a viable population, it may undergo evolutionary change because of genetic drift, climatic differences between the mainland and the island, or the absence of predators and competitors from the mainland. Consequently, body size, coloration, and morphology of island species often evolve rapidly, producing forms unlike any related species elsewhere. Examples include the giant land tortoises of the Galápagos, and the Komodo dragon, a species of monitor lizard from Indonesia. See Polymorphism (genetics), Population genetics, Squamata

If enough morphological change occurs, the island population becomes reproductively isolated from its mainland ancestor, and it is recognized as a unique species. Because long-distance dispersal is relatively infrequent, repeated speciation may occur as populations of the same species successively colonize an island and differentiate. The most celebrated example is Darwin's finches, a group of related species that inhabit the Galápagos Islands and were derived from South American ancestors. The island species have evolved different body and bill sizes, and in some cases occupy unique ecological niches that are normally filled by mainland bird species. The morphology of these finches was first studied by Charles Darwin and constituted important evidence for his theory of natural selection. See Animal evolution, Speciation

Island biogeography theory has been extended to describe the persistence of single-species metapopulations. A metapopulation is a set of connected local populations in a fragmented landscape that does not include a persistent source pool region. Instead, the fragments themselves serve as stepping stones for local colonization and extinction. The most successful application of the metapopulation model has been to spotted owl populations of old-growth forest fragments in the northwestern United States. See Biogeography, Ecological communities, Ecosystem

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
It builds on the theory of island biogeography, which I developed with mathematician Robert MacArthur in the 1960s.
Wilson's The Theory of Island Biogeography (1967) and MacArthur's Geographical Ecology (1972).
The new findings support and extend the theory of island biogeography developed by Robert MacArthur and EO Wilson during the 1960s.
The theory of island biogeography with special reference to the Lake Eric islands.
In the last 20 years, one of the most debated issues in conservation biology has been the size and number of protected areas needed to effectively protect biodiversity, the so-called "SLOSS" (Single Large versus Several Small) debate (Wilkox and Murphy 1985), based on the theory of island biogeography (McArthur and Wilson 1967).
The Theory of Island Biogeography also predicts a long lag between habitat loss and consequent species loss.
Values of z between those two limits will be taken as indicative that the floras are in equilibrium with each other according to the theory of island biogeography (MacArthur and Wilson 1967).
According to the theory of island biogeography, as an island of forest becomes smaller and more isolated from the main body, so the number of species in it decreases until a new equilibrium is reached.
He is a scientific leader, well known for his work on ants and his cocreation (with Robert MacArthur) of the theory of island biogeography. Unlike many scientific leaders, Wilson also has vigorously participated in the public forum.
Wilson quantified in their 1967 book, The theory of island biogeography (Princeton University Press, Princeton, New Jersey), a landmark work that would provide a framework for a new, more theoretically oriented generation of community ecologists.
Wilson in their classic monograph The Theory of Island Biogeography (Princeton University Press, 1967).
Several studies have examined the applicability of the theory of island biogeography to terrestrial habitat patches (Brown, 1971; Blake and Karr, 1984; Doak and Mills, 1994) with many concluding that island biogeographic models fail to adequately describe the nature of species distributions (Middleton and Merriam, 1983; Reed, 1983; McCoy and Mushinsky, 1994; Mills, 1996).