Colonisation (biology)
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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 hereditar ...
by which a
species In biology, a species is the basic unit of Taxonomy (biology), 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 ...
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, a ...
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, villag ...
, 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 last individual of the species, although the capacity to breed ...
. 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) to denote the long-term intrinsic growth rate of a population. One classic scientific model in biogeography 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 b ...
'') in order to achieve longevity. Accordingly, colonisation and extinction are key components of island biogeography, a theory that has many applications in ecology, such as metapopulations.


Scale

Colonisation occurs on several scales. In the most basic form, as biofilm 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 olde ...
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 ...
. 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 or
translocation Translocation may refer to: * Chromosomal translocation, a chromosome abnormality caused by rearrangement of parts ** Robertsonian translocation, a chromosomal rearrangement in pairs 13, 14, 15, 21, and 22 ** Nonreciprocal translocation, transfer ...
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 and colonisation of areas outside Africa according to the recent African origin paradigm, resulting in the extinction of Pleistocene megafauna, 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 and the little egret * the colonisation of Britain by the little egret * the colonisation of western North America by the barred owlLivezey 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 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 bluis ...
* 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 subcontinent of Eurasia and it is located enti ...
of the collared dove * 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 count ...
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 territ ...
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 island ...
in 1995


Dragonflies

*the colonisation of Britain by the small red-eyed damselfly


Moths

*the colonisation of Britain by
Blair's shoulder-knot ''Lithophane leautieri'', the Blair's shoulder-knot, is a moth of the family Noctuidae. It is found in Europe. It originated from the area surrounding the Mediterranean Sea, but gradually moved north. Technical description and variation The win ...


See also

* Colony (biology) *
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 ...
* Pioneer species


References

Community ecology Ecological processes Ecology terminology {{Ecology-stub