Colonisation or colonization is the process in

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...

by which a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

spreads to new areas. Colonisation often refers to ''successful''

immigration Immigration is the international movement of people to a destination country of which they are not natives or where they do not possess citizenship in order to settle as permanent residents or naturalized citizens. Commuters, tourists, ...

where a population becomes integrated into an ecological

community A community is a social unit (a group of living things) with commonality such as place, norms, religion, values, customs, or identity. Communities may share a sense of place situated in a given geographical area (e.g. a country, village, t ...

, having resisted initial local

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the Endling, last individual of the species, although the Functional ext ...

. In

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...

, it is represented by the symbol ''λ'' (lowercase

lambda Lambda (}, ''lám(b)da'') is the 11th letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoenician Lamed . Lambda gave ri ...

) to denote the long-term intrinsic growth rate of a population. One classic

scientific model Scientific modelling is a scientific activity, the aim of which is to make a particular part or feature of the world easier to understand, define, quantify, visualize, or simulate by referencing it to existing and usually commonly accepted ...

biogeography Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

posits that species must continue to colonize new areas through its life cycle (called a ''

taxon cycle Taxon cycles refer to a biogeographical theory of how species evolve through range expansions and contractions over time associated with adaptive shifts in the ecology and morphology of species. The taxon cycle concept was explicitly formulated by ...

'') in order to achieve

longevity The word " longevity" is sometimes used as a synonym for " life expectancy" in demography. However, the term ''longevity'' is sometimes meant to refer only to especially long-lived members of a population, whereas ''life expectancy'' is always ...

. Accordingly, colonisation and extinction are key components of

island biogeography Insular biogeography or island biogeography is a field within biogeography that examines the factors that affect the species richness and diversification of isolated natural communities. The theory was originally developed to explain the pattern of ...

, a theory that has many applications in ecology, such as

metapopulation A metapopulation consists of a group of spatially separated populations of the same species which interact at some level. The term metapopulation was coined by Richard Levins in 1969 to describe a model of population dynamics of insect pests in ...

Scale

Colonisation occurs on several scales. In the most basic form, as

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular po ...

in the formation of communities of

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in old ...

s on surfaces. In small scales such as colonising new sites, perhaps as a result of

environmental change Environmental change is a change or disturbance of the environment most often caused by human influences and natural ecological processes. Environmental changes include various factors, such as natural disasters, human interferences, or animal in ...

. And on larger scales where a species expands its range to encompass new areas. This can be via a series of small encroachments, such as in woody plant encroachment, or by long-distance dispersal. The term range expansion is also used.

Use

The term is generally only used to refer to the spread of a species into new areas by ''natural'' means, as opposed to ''unnatural''

introduction Introduction, The Introduction, Intro, or The Intro may refer to: General use * Introduction (music), an opening section of a piece of music * Introduction (writing), a beginning section to a book, article or essay which states its purpose and ...

or translocation by humans, which may lead to

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

Colonisation events

Large-scale notable pre-historic colonisation events include:

Humans

* the

early human migration Early human migrations are the earliest migrations and expansions of archaic and modern humans across continents. They are believed to have begun approximately 2 million years ago with the early expansions out of Africa by ''Homo erectu ...

and colonisation of areas outside Africa according to the recent African origin paradigm, resulting in the extinction of

Pleistocene megafauna Pleistocene megafauna is the set of large animals that lived on Earth during the Pleistocene epoch. Pleistocene megafauna became extinct during the Quaternary extinction event resulting in substantial changes to ecosystems globally. The role of ...

, although the role of humans in this event is controversial. Some large-scale notable colonisation events during the 20th century are:

Birds

* the colonisation of the

New World The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. ...

by the

cattle egret The cattle egret (''Bubulcus ibis'') is a cosmopolitan species of heron ( family Ardeidae) found in the tropics, subtropics, and warm-temperate zones. It is the only member of the monotypic genus ''Bubulcus'', although some authorities regard ...

and the little egret * the colonisation of

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

by the little egret * the colonisation of western North America by the

barred owl The barred owl (''Strix varia''), also known as the northern barred owl, striped owl or, more informally, hoot owl, is a North American large species of owl. A member of the true owl family, Strigidae, they belong to the genus '' Strix'', whic ...

Livezey KB. 2009b. Range expansion of Barred Owls, part 2: facilitating ecological changes. American Midland Naturalist 161:323–349. * the colonisation of the East Coast of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

by the

Brewer's blackbird Brewer's blackbird (''Euphagus cyanocephalus'') is a medium-sized New World blackbird. It is named after the ornithologist Thomas Mayo Brewer. Description Adult males have black plumage with an iridescent purple head and neck and glossy blui ...

* the colonisation-westwards spread across

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

of the

collared dove ''Streptopelia'' is a genus of birds in the pigeon and dove family Columbidae. These are mainly slim, small to medium-sized species. The upperparts tend to be pale brown and the underparts are often a shade of pink. Many have a characteristic bla ...

* the spread across the eastern USA of the house finch * the expansion into the southern and western areas of

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

by the Hadeda Ibis

Reptiles

* the colonisation of

Anguilla Anguilla ( ) is a British Overseas Territory in the Caribbean. It is one of the most northerly of the Leeward Islands in the Lesser Antilles, lying east of Puerto Rico and the Virgin Islands and directly north of Saint Martin. The terr ...

by Green iguanas following a

rafting event Oceanic dispersal is a type of biological dispersal that occurs when terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between islan ...

in 1995

Dragonflies

*the colonisation of Britain by the

small red-eyed damselfly The small red-eyed damselfly (''Erythromma viridulum'') is a member of the damselfly family Coenagrionidae. It is very similar to the red-eyed damselfly. Appearance The species is a small damselfly, about long, predominantly black with irides ...

Moths

*the colonisation of Britain by Blair's shoulder-knot

References

Community ecology Ecological processes Ecology terminology {{Ecology-stub