Ecological niche

The term ecological niche is the sum of biotic and abiotic environmental factors that affect the survival of a species. Some authors describe the ecological niche of animals as well as their " profession" or " post ".

• 2.1 Fundamental and realized niche
• 2.2 Meaning of the competition factor
• 2.3 Neutral theories
• 2.4 Modern synthesis
• 2.5 Adjustment of niches

Development of the concept

The term ' niche ' in ecological context was first mentioned in a paper of the naturalist Joseph Grinnell in 1917 ( There are scattered earlier documents without resonance). The niche concept Grinnell is based on the key environmental issues: it describes an area of ​​the earth's surface with its specific ecological properties and site characteristics, which is conducive to the survival of the type under consideration. Regardless led the British ecologist Charles Elton in 1927 the term "niche" in a similar sense again. Elton places greater emphasis on the biological interactions, his niche concept is more like the role or function of a species in its community of life, especially her relationship with predators and food resources.

The term in its current usage goes back to an influential article of the zoologist George Evelyn Hutchinson, building on the work of Grinnell's and Elton's. Hutchinson's main innovation was that the niche is not regarded as a property of the environment - in a kind of "fit" or " do not fit ", can optionally also be "empty" remains - but as a property of the type itself

The concept of Hutchinson

Hutchinson's concept is based on the fact known since time immemorial that a species can only live when the environmental factors are within a certain range; these include temperature, moisture, soil conditions, food availability, predation, inter alia, the value range of a factor, such as temperature, can be thought of as a distance (before this route is the way to cold, behind it too hot) (see: Ecological potency). Another factor, such as humidity, then defines an area that is the combination of temperature and humidity, can live in the type ( an application example of the niche of the water flea Daphnia magna offers ). A third factor (for example, pH of the soil ) defining a volume. By adding other factors may lead to a not vivid, but easily comprehensible structure: an n-dimensional hyperspace.

This space is therefore composed of the totality of all environmental factors such as temperature, food, soil, habitat, etc. together, which determine an ecological niche, forming a so-called niche space. The individual factors can be represented graphically as dimensions. An environmental factor represents one dimension; ecological niche is defined by the boundaries within which a sort can live and reproduce, which can be mapped as an area on each graph. It is within this range, an optimum for each factor, with which the species grows best. In practice, there is however, due to the complexity of many life dimensions. A diagram of a realistic multi-dimensional niche you can imagine and therefore difficult to not draw. The n-dimensional hyperspace of environmental factors may therefore be divided for purposes of illustration in two-to three-dimensional niche charts.

Modern applications of the term caused by dissipation and modification of Hutchinsonschen concept. Especially in the Synecology found the niche concept entrance. Here the coherent with the niche concept Termini niche breadth, niche overlap or ecological niches have proven.

Niche overlap means that two species share the same ecological niche. Niche overlap inevitably leads to competition, for example by reducing resources, such as space or food supply, or even light and water in plants. This has a drop in the survival, growth and reproduction of the relevant type (s) result. The associated stress increase - especially by a too small habitat - can possibly lead to the extinction of this type ( s).

The term ecological niche is occasionally misunderstood because the term " niche " colloquially generally a space or a place is connected. However, the ecological niche is not a spatial description, as opposed to the terms habitat (or location ) and habitat, which denote a physical location. In fact, the ecological niche is a functional term that refers to the "ecological role " played by the species in the ecosystem under consideration. He thus describes the biotic and abiotic conditions, environmental factors and evolutionary factors of death or survival of this species in the ecosystem are important. It follows that so defined networks can not be " occupied ". Rather, they are " made ​​", by interaction between the organisms of a species with its environment.

Niche theory and competition between species

The artbezogene definition of the ecological niche naturally can be done independently for each species. Other species are indirectly (as environmental factors, for example, as predator or as food ) in the niche definition, but play no direct role. Comparing the thus found ecological niches of different species, they can be completely separated from each other when the species share no area of a habitat. The niche thus formed are but overlap more or less frequently. This means that part of the recess space can be used by the two species. The niche space of a species in the presence of other species will therefore differ from those without it. It may be larger ( in symbiotic or mutualistic relationships ), more commonly it will, however, be smaller due to competition or other antagonisms.

Fundamental and realized niche

Therefore There are two basic concepts of ecological niche:

Importance of the competition factor

Since competition between species in the opinion of many ecologists among the essential factors that determine the natural communities, a substantial scope of the niche theory lies in the consideration of this competition. The starting point is the exclusion of competition principle: So, in a habitat not coexist two types with the same life claims. The competitive superior way is the losing displace. Does that principle in natural communities, it is in need of explanation why there are so many types obviously can get along without that most of them would supplanted by superior competitors. Hutchinson himself spoke, for example, for the phytoplankton of lakes, which a handful of essential resources to compete in a seemingly homogeneous habitat ( in essence, light, phosphorus, nitrogen) and yet is very diverse, from the " paradox of the plankton "

Translated into the language of niche theory means exclusion of competitors, that the niches of two species for at least one of these species completely overlap ( they need not be identical: A niche can be completely enclosed by another ). Has one of the species as a percentage of niche space that the superior competitor can not settle, she has there a refuge. Thus, the survival of the species is indeed backed up, but: a common occurrence would still be impossible.

Within the niche theory, there are several possible solutions to this problem.

• Spatial variability: The habitat consists of partial habitats that differ in one or more environmental factors. In every part of Habitat is another way superior to competitive.
• Temporal variability: The living conditions change during the season, from year to year or long term and thus favor each other species. The superior species will not have enough time to displace their competitors because the conditions have changed again by then. Thus, the species have a "temporal niche ".
• Trade- offs: There are no " super species ", the other species were superior in all respects. Advantages in one area are "bought" by disadvantages in other (English: trade-off ). Thus, a type not simultaneously have particularly large and particularly many seeds. A plant can be competitive over lay at high nitrogen content of the soil, but are subject to lower.
• Modification by biological interactions: The competitive ability of a species can be influenced by other species, especially by predators. In the presence of a particular predator can an otherwise competitive inferior species are indirectly promoted, for example, even if the species itself is part of the prey spectrum when the competitor even more suffering to him. Grazing by the predator can reduce the population density of competitors so far that the factor is the normally competes for all competitors is sufficiently available.
• Ecological niches: species can avoid the inter-specific competition. For example, it has been observed that species with common occurrence differ strongly in their body than in its sole occurrence ( "character displacement" ). A famous example are different species of Darwin 's finches on the Galapagos Islands. For explanation of the ecological niches of different species has been proposed a " diffuse " competition from related species

Neutral theories

As an alternative to the options mentioned denies a group of ecologists, the paramount importance of the competition. In this case, move overlapping niches are no longer a problem that would apply to solve it. Niches and ecological niches lose their central role in structuring communities in these theories. The local composition is characterized by randomly determined ( " stochastic " ) factors: va Immigration and extinction rates, colonization speed, random sequence changes of the incoming species (and in evolutionary periods: reappearance of species). This " neutral theory " has been elaborated especially by working ecologist Stephen P.Hubbell. Are a modern overview of this. Also in the neutral theory of competition factor is implicitly taken into account because the available space is limited for each individual. Establishment of a new individual is only possible in a gap that is released upon the death of an elderly. Such "gaps lottery " to establish niches had previously been proposed to explain the species richness of calcareous grasslands. The ecologist PJGrubb has coined the term " regeneration niche "

Modern syntheses

The new version of the neutral theory has sparked fierce controversy in ecology. Although the theory is rejected in its pure form by most ecologists, it has contributed to a modification of the niche theory. In most modern versions of stochastic elements in the ( completely deterministic in its core ) niche theory are introduced. Possible explanations for species richness are then passed through a combination of both factors (for example ). Other possibilities such as multiple equilibria (for example ). A modern overview of the niche theory provides, for example,

Adaptation of niches

The ecological ecological niches of species is considered more flexible than in the previous theories according to recent findings. One study showed in 2011 that differ hunting habits of diving seabirds greatly both between species and within a species. The ecological niches are not rigidly fixed: Different habitats, avoidance of competition with neighbors or the evasion of predators lead even within a species to different behavior. Scientists at the MPI Radolfzell selected seabirds as the object, as they are bound to breed on land and in particular at this time many animals have to share the space and the food. Since several similar species breed together in their claims on an island was the question of how they differ in ecological niches. The data showed that the spatial and temporal distribution of birds can vary greatly even within a species. The ecological niches within a species by specializations alleviate competition. The animals appear in geographically far-flung sea areas at different depths and temperature of food.

Application of niche theory to predict Artarealen

An increasing use is the niche theory in biogeographical research. Here known presence of a species with measured environmental factors (especially climate) are correlated to as predicted from the ecological niche of the species during their potential area can, by transferring the results to areas with similar environmental factors, where the species had not yet been established. These models are called habitat modeling. Particularly common is this approach to predict the impacts of climate change. For this purpose, a model of the area under the changed climate conditions, according to the present climate models constructed. Basis of the processing is the observation that the ecological ecological niches of a species hardly changed in short periods of time. It is therefore likely that the type of migration shifts their area, as they adaptively adjusts to the spot to the new conditions. It speaks clearly of the " climatic envelope " (English: climatic envelope ) of the Article on possible dangers and fallacies with this method make some American ecologists attention, which can thus construct an area for the Yeti.

Application of the concept of niche outside of ecology

The concept of the ecological niche has outside of Ecology found wide use. The popular concept that is so circumscribed, however usually very different from the scientific use. An "ecological niche " in general parlance, is more like a quiet place outside the harsh winds of competition, in which one, although a limited but may lead halfway secure existence. The politician Günter Gaus was able to distinguish the company of the former GDR as a " niche society". A special career has been able to take the term in economics, in particular the market psychology, in which he was introduced by the psychologist Bert mirror ( as a conscious transfer of the ecological niche in the economic sphere ). The common terms such as " market niche " or " niche product " so go back to the transfer of an ecological approach to the economy. This ambivalence is held by business journalists, especially in the context of so-called "eco- products " alive, like the headlines to puns in the way of "Biodiesel - get out of the niche " initiate.