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 ?
It builds on the theory of island biogeography, which I developed with mathematician Robert MacArthur in the 1960s.
Between 1956 and 1996 his research led to his landmark theories of island biogeography, socio-biology and the role of biology in the human culture, which won his first Pulitzer Prize for On Human Nature in 1979.
Island biogeography of bats in Baja California, Mexico: patterns of bat species richness in a near-shore archipelago.
These factors are certainly important in the light of (i) island biogeography theory (factors (1) and (2); see McArthur & Wilson 1963), and in the light of the deep human intervention that has characterized the islands of the Tuscan Archipelago, and the Mediterranean islands in general, since centuries (factor (3); see Masseti 2009a, b).
2008--Inferring dispersal: a Bayesian approach to phylogeny-based island biogeography, with special reference to the Canary Islands--J.
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.
The book is well written, thoroughly researched, and balanced in its approach to conservation and responsible forest management, taking into account dependencies of aboriginal peoples on the rainforest's life-giving ecosystem services (Chapter 5); the historical and transitioning economics of the region, including changes in the forestry sector (Chapter 9); the role of island biogeography and glaciation in rainforest biodiversity (Chapter 2); riparian ecology (Chapter 3) and watershed planning (Chapter 8), and disturbance ecology (Chapter 4).
Wilson's The Theory of Island Biogeography (1967) and MacArthur's Geographical Ecology (1972).
Given the above, the theory of island biogeography proposed by MacArthur and Wilson (1967) presents relevant considerations likely to be applied to bromeliads, once the tanks of these plants can be considered as isolated islands colonized by many species.