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

References in periodicals archive ?
Examples of the MacArthur and Wilson (1967) concepts of island biogeography will be discussed where appropriate.
l Contributing to traditional knowledge, the scientific understanding of island biogeography, conservation biology, climate change and other subject areas.
Early studies in island biogeography found the closer an island is to other islands, the greater the opportunity for connection and interaction and the greater the species diversity.
But his contributions to science include a range of original concepts--including development of theories about island biogeography, population biology, sociobiology, and evolutionary biology--that have become pivotal to our understanding of how the natural world and human behavior work.
He is best known for such celebrated nonfiction titles as The Song of the Dodo: Island Biogeography in an Age of Extinctions (1996) and Monster of God: The Man-Eating Predator in the Jungles of History and the Mind (2003).
Some general guidelines for strong interactions begin to emerge relative to ecosystem complexity and links with the theory of island biogeography, and strength of relationships across trophic levels can be generalized.
His early research on insects on small islands in Florida had assessed the theory of island biogeography, which proposed that the number of species found on an undisturbed island was determined by a balance between ongoing immigration and extinction.
2006, 'No pig atoll: Island biogeography and the extirpation of a Polynesian domesticate', Asian Perspectives, 45(1):78-95.
Not that I'm an expert on biogeography, but it's not news to me that Darwin's trip to the Galapagos Islands was pivotal to the development of his theory, that island biogeography holds clues to evolutionary change, and that plate tectonics, which McCarthy covers in some detail, explains the movement of continents.
Klinkenberg (1983, 1988, 1992, 2001) examined the flora of the Erie Islands using the theory and methods of island biogeography (McArthur and Wilson 2001).
DVM: (Omaha's Henry Doorly Zoo) Tireless conservation advocate of island biogeography, including the discovery of 30 percent of known lemurs to date.