Naturalisation (or naturalization) is the ecological phenomenon through which a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

, or

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

of exotic (as opposed to native) origin integrates into a given

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

, becoming capable of reproducing and growing in it, and proceeds to disseminate spontaneously. In some instances, the presence of a species in a given ecosystem is so ancient that it cannot be presupposed whether it is native or introduced. Generally, any

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived ther ...

may (in the wild) either go extinct or naturalise in its new environment. Some populations do not sustain themselves reproductively, but exist because of continued influx from elsewhere. Such a non-sustaining population, or the individuals within it, are said to be adventive. Cultivated plants, sometimes called nativars, are a major source of adventive populations.

Botany

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

, naturalisation is the situation in which an exogenous plant reproduces and disperses on its own in a new environment. For example, northern white cedar is naturalised in the United Kingdom, where it reproduces on its own, while it is not in France, where human intervention via cuttings or seeds are essential for its dissemination. Two categories of naturalisation are defined from two distinct parameters: one, archaeonaturalised, refers to introduction before a given time (introduced over a hundred years ago), while the second, amphinaturalised or eurynaturalised, implies a notion of spatial extension (taxon assimilated indigenous and present over a vast space, opposed to stenonaturalised).

Degrees of naturalisation

The degrees of naturalisation are defined in relation to the status of nativity or introduction of

s or species: * Accidental taxon: non- native taxon growing spontaneously, which appears sporadically as a result of accidental introduction due to human activities (as opposed to intentional introductions) * Subspontaneous taxon: taxon naturalised following an introduction of accidental origin (fortuitous introduction linked to human activities) or unknown, and which, after

acclimatization Acclimatization or acclimatisation ( also called acclimation or acclimatation) is the process in which an individual organism adjusts to a change in its environment (such as a change in altitude, temperature, humidity, photoperiod, or pH), ...

, can reproduce like native plants but is still poorly established * Spontaneous taxon: native or non-native taxon growing and reproducing naturally, without intentional human intervention in the territory considered, and is well established (mixes with local flora or fauna)

Zoology

Animal naturalisation is mainly carried out through

breeding Breeding is sexual reproduction that produces offspring, usually animals or plants. It can only occur between a male and a female animal or plant. Breeding may refer to: * Animal husbandry, through selected specimens such as dogs, horses, and rab ...

and by

commensalism Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fr ...

following human migrations. The concerned species are thus: * either introduced voluntarily into an ecosystem where they are not native; * either accidentally introduced or become

feral A feral (; ) animal or plant is one that lives in the wild but is descended from domesticated individuals. As with an introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in som ...

; * or by naturally following human migratory flows by

(eg: arrival of

house sparrow The house sparrow (''Passer domesticus'') is a bird of the Old World sparrow, sparrow family Passeridae, found in most parts of the world. It is a small bird that has a typical length of and a mass of . Females and young birds are coloured pa ...

in Western Europe following

Huns The Huns were a nomadic people who lived in Central Asia, the Caucasus, and Eastern Europe between the 4th and 6th centuries AD. According to European tradition, they were first reported living east of the Volga River, in an area that was par ...

, and previously in Eastern Europe from Asia Minor in Antiquity). It sometimes happens that a naturalised species hybridizes with a native.

Introduction and origin areas

The introduction site or introduction area is the place or, in a broadlier way, the new environment where the candidate species for naturalisation takes root. It is generally opposed to the ''origin area'', where this same species is native. There is also a more ambiguous notion that is the "natural distribution area" or "natural distribution range", particularly when it comes to anthropophilic species or some species benefiting from anthropogenic land settlement (canals, bridges, deforestation, etc.) that have connected two previously isolated areas (e.g. the

Suez Canal The Suez Canal (; , ') is an artificial sea-level waterway in Egypt, Indo-Mediterranean, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia (and by extension, the Sinai Peninsula from the rest ...

, which causes Lessepsian migration).

Impact on the ecosystem

Naturalisation is sometimes done with human help in order to replace another species having suffered directly or indirectly from anthropogenic activities, or deemed less profitable for human use. Naturalised species may become

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

if they become sufficiently abundant to have an adverse effect on native species (e.g. microbes affected by invasive plants) or on biotope. Examples of naturalised species that have become invasive include the European rabbit, native to Europe and which abounds in Australia; or the Japanese knotweed which is invading Europe and America where it is considered to be amongst the one hundred most invasive species in the 21st century. Apart from direct competition between native and introduced populations,

genetic pollution Genetic pollution is a term for uncontrolled gene flow into wild populations. It is defined as "the dispersal of contaminated altered genes from genetically engineered organisms to natural organisms, esp. by cross-pollination", but has come to be ...

by hybridization can add up cumulatively to environmental effects that compromise the conservation of native populations. Some naturalised species, such as palms, can act as ecosystem engineers, by changing the habitat and creating new niches that can sometimes have positive effects on an ecosystem. Potential and/or perceived positive impacts of naturalised species are less studied than potential and/or perceived negative impacts. However, the impact on local species is not easy to assess in a short period. For instance, the African sacred ibis ('' Threskiornis aethiopicus'') escaped in 1990 from an animal park in

Morbihan The Morbihan ( , ; ) is a departments of France, department in the administrative region of Brittany (administrative region), Brittany, situated in the northwest of France. It is named after the Gulf of Morbihan, Morbihan (''small sea'' in Breton ...

(France), gave rise to an eradication campaign in 2008. In 2013, however, the CNRS stated that this bird species is not a threat in France, and may even promote

Eurasian spoonbill The Eurasian spoonbill (''Platalea leucorodia''), or common spoonbill, is a wading bird of the ibis and spoonbill family Threskiornithidae, native to Europe, Africa and Asia. The species is partially migratory with the more northerly breeding popu ...

and limit the development of the invasive Louisiana crayfish.

References