A metapopulation consists of a group of populations of a species separated in space that interact at a certain level. The term was coined by Richar Levins in 1969 to describe a population dynamics model of insect pests of agriculture, but the idea has spread and is more widely applied to species present in naturally or artificially fragmented habitats. According to Levins "it consists of a population of populations."
It is generally considered that a metapopulation is composed of several different populations together with areas of suitable habitat that are not currently occupied. In classical metapopulation theory, each population operates in relative independence from other populations and may eventually be extinguished by demographic stochastic phenomena (random fluctuations in population size due to demographic events); the smaller the population, the greater the possibilities of inbreeding depression and tendency to extinction. Although individual populations have a limited life span, the metapopulation as a whole is more stable because immigrants from a thriving population can recolonize another population that is declining or occupying habitats left by populations that have become extinct.
At first the theory of metapopulations applied only to terrestrial ecosystems; then it was extended to marine ecosystems.In this case, the term "sub-populations rather than local populations is sometimes used." Most examples of marine metapopulations are applied to sedentary species occupying limited portions of habitats with local recruitment and with recruitments from other local populations that are part of the metapopulation.
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