The concept of ecological niche is associated with. Ecological niche

Detailed solution to paragraph § 76 in biology for 10th grade students, authors Kamensky A.A., Kriksunov E.A., Pasechnik V.V. 2014

1. What is a habitat?

Answer. Habitat (habitat) is a set of biotic, abiotic and anthropogenic (if any) environmental factors in any specific territory or water area, formed on the site of the primary complex of abiotic factors - ecotope. The habitat of a species or population is an important component of his/her ecological niche. In relation to terrestrial animals, the term is considered synonymous with the concepts of station (habitat of a species) and biotope (habitat of a community).

Habitats characterized by different severity of environmental factors, but having similar vegetation cover, are called biologically equivalent. Their existence is possible due to the partial compensation of factors by each other.

T. Southwood (1977) proposed classifying habitats according to the nature of changes in factors over time, highlighting the following:

unchanged - environmental conditions remain favorable indefinitely;

predictably seasonal - there is a regular change of favorable and unfavorable periods;

unpredictable - favorable and unfavorable periods have different durations;

ephemeral - with a short favorable period.

2. What is a food chain?

Answer. Food (trophic) chain - a series of species of plants, animals, fungi and microorganisms that are connected to each other by the relationship: food - consumer (a sequence of organisms in which a gradual transfer of matter and energy occurs from source to consumer).

The organisms of the subsequent link eat the organisms of the previous link, and thus a chain transfer of energy and matter occurs, which underlies the cycle of substances in nature. With each transfer from link to link, a large part (up to 80-90%) of the potential energy is lost, dissipated in the form of heat. For this reason, the number of links (types) in the food chain is limited and usually does not exceed 4-5.

3. What is interspecific struggle?

Questions after § 76

1. What is the difference between the concepts of “habitat” and “ecological niche”?

Answer. The position of a species that it occupies in the biogeocenosis, the complex of its connections with other species and requirements for abiotic environmental factors is called an ecological niche. The concept of "ecological niche" should be distinguished from the concept of "habitat". In the latter case, we are talking about the part of space where the species lives and where the necessary abiotic conditions for its existence exist. The ecological niche of a species depends not only on abiotic conditions, it characterizes the entire lifestyle that a species can lead in a given community. According to the figurative expression of ecologist Yu. Odum, a habitat is the address of a species, and an ecological niche is its “profession.” There are fundamental (or potential) and realized niches. A fundamental ecological niche is a set of optimal conditions under which a given species can exist and reproduce. Realized niche - the conditions where a species actually occurs in a given ecosystem; it always forms some part of the fundamental niche.

For the reproduction and long-term existence of many animal species, the delimitation of niches at different stages of ontogenesis is of great importance: caterpillars and adults of lepidoptera, larvae and beetles of the May beetle, tadpoles and adult frogs do not compete with each other, since they differ in habitat and are part of different food chains.

Interspecific competition leads to a narrowing of the ecological niche and does not allow its potential to manifest itself. Intraspecific competition, on the contrary, contributes to the expansion of the ecological niche. In connection with the increase in the number of the species, the use of additional food begins, the development of new habitats, and the emergence of new biocenotic connections.

2. Can different species occupy the same ecological niche?

Answer. No they can't. A large number of organisms of different species live in one habitat. For example, a mixed forest is a habitat for hundreds of species of plants and animals, but each of them has its own and only one “profession” - an ecological niche.

In the forest, elk and squirrel have similar habitats, but their niches are completely different: the squirrel lives mainly in the crowns of trees, feeds on seeds and fruits, and reproduces there. The entire life cycle of an elk is associated with the subcanopy space: feeding on green plants or their parts, reproduction and shelter in thickets.

Elements of an ecological niche:

food (types);

time and methods of nutrition;

breeding place;

place of shelter.

Ecological niches exist according to certain rules:

the wider the requirements (limits of tolerance) of a species to any or many environmental factors, the larger the space that it can occupy in nature, and therefore the wider its distribution;

if the regime of any, at least one, environmental factor in the habitat of individuals of one species has changed in such a way that its values go beyond the limits of the niche, then this means the destruction of the niche, that is, the limitation or impossibility of preserving the species in a given habitat. Other important patterns are also associated with the concept of “ecological niche” - each species has its own, unique ecological niche, i.e., as many species on Earth, so many ecological niches (2.2 million species of living organisms, of which 1.7 million species of animals). Two different species (even very close ones) cannot occupy the same ecological niche in space;

in each ecosystem there are species that claim the same niche or its elements (food, shelter). In this case, competition is inevitable, the struggle to own a niche. Such relationships are reflected by Gause's rule: if two species with similar requirements for the environment (nutrition, behavior, breeding sites) enter into a competitive relationship, then one of them must die or change its lifestyle and occupy a new ecological niche.

An ecological niche is the totality of all the requirements of a species (population) to environmental conditions (the composition and regime of environmental factors) and the place where these requirements are met.

The ecological niches of co-living species may partially overlap, but never completely coincide, because the law of competitive exclusion comes into play.

3. Can one species occupy different ecological niches? What does this depend on?

4. What is the importance of ecological niches in the life of a community?

Answer. The concept of an ecological niche is very useful for understanding the laws of coexistence of species. For example, every green plant, taking one or another part in the formation of biogeocenosis, ensures the existence of a number of ecological niches. Among them there may be niches that include organisms that feed on root tissues (root beetles) or leaf tissues (leaf beetles and sap suckers), flowers (flower beetles), fruits (fruit eaters), root secretions (eccrisotrophs), etc. Together they form an integral system of diverse uses plant mass of the body. Moreover, all heterotrophs that eat plant biomass almost do not compete with each other.

Each of these niches includes groups of organisms that are heterogeneous in species composition. For example, the ecological group of root beetles includes both nematodes and the larvae of some beetles (May beetles, click beetles), and the niche of plants sucking plant juices includes bugs and aphids.

Ecological niches of animals feeding on plant biomass

Groups of species in a community that have similar functions and niches of the same properties are called guilds by some authors (guild of root eaters, guild of night predators, guild of scavengers, etc.).

Consider Figure 122. Do herbivores occupy the same or different niches on the African savanna? Justify your answer. Consider Figure 123. Do the dragonfly and its larva occupy the same or different niches? Justify your answer.

Answer. In the savanna, animals occupy different ecological niches. An ecological niche is a place occupied by a species in a biocenosis, including a complex of its biocenotic connections and requirements for environmental factors. The term was coined in 1914 by J. Grinnell and in 1927 by Charles Elton.

An ecological niche is the sum of factors for the existence of a given species, the main one of which is its place in the food chain.

An ecological niche can be:

fundamental - determined by the combination of conditions and resources that allow the species to maintain a viable population;

realized - the properties of which are determined by competing species.

This difference emphasizes that interspecific competition leads to a decrease in fertility and viability and that there may be a part of the fundamental ecological niche in which a species, as a result of interspecific competition, is no longer able to live and reproduce successfully.

An ecological niche cannot be empty. If a niche becomes empty as a result of the extinction of a species, it is immediately filled by another species.

The habitat usually consists of separate areas ("patches") with favorable and unfavorable conditions; these spots are often only temporarily accessible, and they appear unpredictably in both time and space.

Vacant areas or habitat “gaps” occur unpredictably in many biotopes. Fires or landslides can lead to the formation of wastelands in forests; a storm can expose an open area of the seashore, and voracious predators anywhere can exterminate potential victims. These vacated areas are invariably repopulated. However, the very first settlers will not necessarily be those species that are able to successfully compete with and displace other species over a long period of time. Therefore, the coexistence of transient and competitive species is possible as long as uninhabited areas appear with suitable frequency. A transient species is usually the first to colonize a vacant area, colonize it, and reproduce. A more competitive species colonizes these areas slowly, but once colonization has begun, over time it defeats the transient species and reproduces.

The study of ecological niches is of great practical importance. When introducing foreign species into the local flora and fauna, it is necessary to find out what ecological niche they occupy in their homeland, and whether they will have competitors in the places of introduction. The wide distribution of muskrats in Europe and Asia is explained precisely by the absence of rodents with a similar lifestyle in these regions.

In related species living together, there is a very fine delineation of ecological niches. Thus, ungulates grazing in African savannas use pasture food in different ways: zebras mainly pick off the tops of grasses, wildebeests feed on what zebras leave for them, gazelles pluck the lowest grasses, and topi antelopes are content with dry stems left behind by other herbivores. Due to the division of niches, the total bioproductivity of such a complex herd in terms of species composition increases. A peasant herd consisting of cows, sheep, and goats uses meadows and pastures much more efficiently, from an environmental point of view, than a single-species herd; monoculture is the least effective way of farming.

If we compare an adult insect and dragonfly larvae, we can draw the following conclusions:

1) Larvae usually serve as the dispersal stage that ensures the spread of the species.

2) Larvae differ from adults both in the biology of nutrition, and in their habitat, and in their methods of movement (a flying dragonfly and its swimming larva), and behavioral characteristics. Thanks to this, one species can take advantage of the opportunities provided by two ecological niches throughout its entire life cycle. This increases the chances of survival of the species.

3) they can adapt to various conditions awaiting them in their second life, they have physiological endurance.

One of the fundamental concepts in modern ecology is the concept of ecological niche. For the first time, zoologists started talking about the ecological niche. In 1914, the American zoologist-naturalist J. Grinnell and in 1927, the English ecologist C. Elton, used the term “niche” to define the smallest unit of distribution of a species, as well as the place of a given organism in the biotic environment, its position in food chains.

A generalized definition of an ecological niche is the following: this is the place of a species in nature, determined by a combined set of environmental factors. An ecological niche includes not only the position of a species in space, but also its functional role in the community.

- this is a set of environmental factors within which a particular species of organism lives, its place in nature, within which a given species can exist indefinitely.

Since a large number of factors should be taken into account when determining an ecological niche, the place of a species in nature, described by these factors, is a multidimensional space. This approach allowed the American ecologist G. Hutchinson to give the following definition of an ecological niche: it is part of an imaginary multidimensional space, the individual dimensions of which (vectors) correspond to the factors necessary for the normal existence of a species. At the same time, Hutchinson identified a niche fundamental, which a population can occupy in the absence of competition (it is determined by the physiological characteristics of organisms), and the niche implemented, those. part of the fundamental niche within which a species actually occurs in nature and which it occupies in the presence of competition with other species. It is clear that the realized niche, as a rule, is always smaller than the fundamental one.

Some ecologists emphasize that organisms must not only occur within their ecological niche, but also be capable of reproducing. Since there is species specificity to any environmental factor, the ecological niches of species are specific. Each species has its own characteristic ecological niche.

Most species of plants and animals can exist only in special niches in which certain physicochemical factors, temperature and food sources are maintained. After the destruction of bamboo began in China, for example, the panda, whose diet consists of 99% of this plant, found itself on the verge of extinction.

Species with common niches can easily adapt to changing environmental conditions, so the risk of their extinction is low. Typical representatives of species with common niches are mice, cockroaches, flies, rats and people.

G. Gause’s law of competitive exclusion for ecologically similar species in the light of the doctrine of the ecological niche can be formulated as follows: two species cannot occupy the same ecological niche. Exit from competition is achieved by diverging requirements for the environment or, in other words, by delimiting the ecological niches of species.

Competing species that live together often “share” available resources to reduce competition. A typical example is the division into animals that are active during the day and those that are active at night. Bats (every fourth mammal in the world belongs to this suborder of bats) share airspace with other insect hunters - birds, using the cycle of day and night. It is true that bats have several relatively weak competitors, such as owls and nightjars, which are also active at night.

A similar division of ecological niches into day and night “shifts” is observed in plants. Some plants bloom flowers during the day (most wild species), others at night (Lubka bifolia, fragrant tobacco). At the same time, nocturnal species also emit a scent that attracts pollinators.

The ecological amplitudes of some species are very small. Thus, in tropical Africa, one species of worm lives under the eyelids of a hippopotamus and feeds exclusively on the tears of this animal. It is difficult to imagine a narrower ecological niche.

Species ecological niche concept

The position of a species that it occupies in the general system of biocenosis, including the complex of its biocenotic connections and requirements for abiotic environmental factors, is called ecological niche of the species.

The concept of ecological niche has proven to be very fruitful for understanding the laws of coexistence between species. The concept of “ecological niche” should be distinguished from the concept of “habitat”. In the latter case, we mean that part of the space that is inhabited by the species and which has the necessary abiotic conditions for its existence.

The ecological niche of a species depends not only on abiotic environmental conditions, but also, no less, on its biocenotic environment. This is a characteristic of the lifestyle that a species can lead in a given community. There are as many ecological niches as there are species of living organisms on Earth.

Competitive exclusion rule can be expressed in such a way that two species do not coexist in the same ecological niche. Exit from competition is achieved due to divergence of requirements for the environment, changes in lifestyle, which is the delimitation of the ecological niches of species. In this case, they acquire the ability to coexist in the same biocenosis.

Division of ecological niches by co-living species with their partial overlap - one of the mechanisms of sustainability of natural biocenoses. If any of the species sharply reduces its numbers or drops out of the community, others take on its role.

The ecological niches of plants, at first glance, are less diverse than those of animals. They are clearly defined in species that differ in nutrition. During ontogenesis, plants, like many animals, change their ecological niche. As they age, they use and transform their environment more intensively.

Plants have overlapping ecological niches. It intensifies in certain periods when environmental resources are limited, but since species use resources individually, selectively and with different intensities, competition in stable phytocenoses is weakened.

The richness of ecological niches in a biocenosis is influenced by two groups of reasons. The first is the environmental conditions provided by the biotope. The more mosaic and diverse the biotope, the more species can demarcate their ecological niches in it.

Ecological niche

1. The concept of “ecological niche”

2. Ecological niche and ecosystems

Conclusion

Literature

1. The concept of “ecological niche”

Ecological niche , the place occupied by a species (more precisely, its population) in a community (biocenosis). The interaction of a given species (population) with partners in the community of which it is a member determines its place in the cycle of substances determined by food and competitive relationships in the biocenosis. The term “Ecological niche” was proposed by the American scientist J. Grinell (1917). The interpretation of an ecological niche as the position of a species in the food chains of one or several biocenoses was given by the English ecologist C. Elton (1927). Such an interpretation of the concept of an ecological niche allows us to give a quantitative description of the ecological niche for each species or for its individual populations. To do this, the abundance of the species (number of individuals or biomass) is compared in the coordinate system with indicators of temperature, humidity or any other environmental factor. In this way, it is possible to identify the optimum zone and the limits of deviations tolerated by the type - the maximum and minimum of each factor or set of factors. As a rule, each species occupies a certain ecological niche, for the existence in which it is adapted throughout the course of evolutionary development. The place occupied by a species (its population) in space (spatial ecological niche) is more often called habitat.

Ecological niche - the spatiotemporal position of an organism within the ecosystem (where, when and what it eats, where it makes a nest, etc.)

At first glance, it seems that animals must compete with each other for food and shelter. However, this rarely happens, because they occupy different ecological niches. Example: woodpeckers extract larvae from under the bark using sparrow grain. Both flycatchers and bats catch midges, but at different times - day and night. The giraffe eats leaves from the treetops and does not compete with other herbivores.

Each animal species has its own niche, which minimizes competition with other species. Therefore, in a balanced ecosystem, the presence of one species usually does not threaten another.

Adaptation to different niches is associated with the action of the law of the limiting factor. Trying to use resources outside of its niche, the animal faces stress, i.e. with increasing resistance of the medium. In other words, in its own niche its competitiveness is great, but outside it it weakens significantly or disappears altogether.

The adaptation of animals to certain niches took millions of years and occurred differently in each ecosystem. Species introduced from other ecosystems can cause the extinction of local ones precisely as a result of successful competition for their niches.

1. Starlings, brought to North America from Europe, due to their aggressive territorial behavior, displaced the local “blue” birds.

2. Feral donkeys have poisoned desert ecosystems, displacing bighorn sheep.

3. In 1859, rabbits were brought to Australia from England for sport hunting. Natural conditions turned out to be favorable for them, and local predators were not dangerous. As a result

4. Farmers are looking for methods to combat a weed that has not previously been found in the Nile Valley. A short plant with large leaves and powerful roots has been attacking the cultivated lands of Egypt for several years. Local agronomists consider it an extremely active pest. It turns out that this plant is known in Europe under the name “country horseradish”. It was probably brought by Russian specialists who were building a metallurgical plant.

The concept of ecological niche also applies to plants. Like animals, their competitiveness is high only in certain conditions.

Example: Plane trees grow along river banks and in floodplains, oak trees grow on slopes. Sycamore is adapted to waterlogged soil. Sycamore seeds spread upslope and this species can grow there in the absence of oak trees. Similarly, when acorns fall into the floodplain, they die due to excess moisture and are not able to compete with plane trees.

Human ecological niche - composition of air, water, food, climatic conditions, level of electromagnetic, ultraviolet, radioactive radiation, etc.

2. Ecological niche and ecosystems

At different times, different meanings were attributed to the concept of an ecological niche. At first, the word “niche” denoted the basic unit of distribution of a species within the space of an ecosystem, dictated by the structural and instinctive limitations of a given species. For example, squirrels live in trees, moose live on the ground, some bird species nest on branches, others in hollows, etc. Here the concept of ecological niche is interpreted mainly as a habitat, or spatial niche. Later, the term “niche” was given the meaning of “the functional status of an organism in a community.” This mainly concerned the place of a given species in the trophic structure of the ecosystem: type of food, time and place of feeding, who is a predator for a given organism, etc. This is now called the trophic niche. Then it was shown that a niche can be considered as a kind of hypervolume in a multidimensional space built on the basis of environmental factors. This hypervolume limited the range of factors in which a given species could exist (hyperdimensional niche).

That is, in the modern understanding of an ecological niche, at least three aspects can be distinguished: the physical space occupied by an organism in nature (habitat), its relationship to environmental factors and to neighboring living organisms (connections), as well as its functional role in the ecosystem. All these aspects are manifested through the structure of the organism, its adaptations, instincts, life cycles, life “interests”, etc. The right of an organism to choose its ecological niche is limited by a rather narrow framework assigned to it from birth. However, its descendants can claim other ecological niches if appropriate genetic changes have occurred in them.

Using the concept of ecological niche, Gause's rule of competitive exclusion can be rephrased as follows: two different species cannot occupy the same ecological niche for a long time or even enter the same ecosystem; one of them must either die or change and occupy a new ecological niche. By the way, intraspecific competition is often greatly reduced precisely because at different stages of the life cycle many organisms occupy different ecological niches. For example, a tadpole is a herbivore, and adult frogs living in the same pond are predators. Another example: insects in the larval and adult stages.

A large number of organisms of different species can live in one area in an ecosystem. These may be closely related species, but each of them must occupy its own unique ecological niche. In this case, these species do not enter into competitive relationships and, in a certain sense, become neutral to each other. However, often the ecological niches of different species may overlap in at least one aspect, for example, habitat or diet. This leads to interspecific competition, which is usually not severe and contributes to the clear delineation of ecological niches.

Thus, in ecosystems, a law similar to the Pauli exclusion principle in quantum physics is implemented: in a given quantum system, more than one fermion (particles with half-integer spin, such as electrons, protons, neutrons, etc.) cannot exist in the same quantum state. ). In ecosystems, there is also a quantization of ecological niches that tend to be clearly localized in relation to other ecological niches. Within a given ecological niche, that is, within the population that occupies this niche, differentiation continues into more specific niches that are occupied by each specific individual, which determines the status of this individual in the life of this population.

Does similar differentiation occur at lower levels of the system hierarchy, for example, at the level of a multicellular organism? Here we can also distinguish different “types” of cells and smaller “bodies”, the structure of which determines their functional purpose within the body. Some of them are immobile, their colonies form organs, the purpose of which makes sense only in relation to the organism as a whole. There are also mobile simple organisms that seem to live their own “personal” life, which nevertheless fully satisfies the needs of the entire multicellular organism. For example, red blood cells do only what they “can” do: they bind oxygen in one place and release it in another place. This is their “ecological niche”. The vital activity of each cell of the body is structured in such a way that, while “living for itself,” it simultaneously works for the benefit of the entire organism. Such work does not tire us at all, just as we are not tired by the process of eating, or doing what we love (if, of course, all this is in moderation). The cells are designed in such a way that they simply cannot live any other way, just as a bee cannot live without collecting nectar and pollen from flowers (probably this brings her some kind of pleasure).

Thus, all of nature “from bottom to top” seems to be permeated with the idea of differentiation, which in ecology has taken shape in the concept of an ecological niche, which in a certain sense is analogous to an organ or subsystem of a living organism. These “organs” themselves are formed under the influence of the external environment, that is, their formation is subject to the requirements of the supersystem, in our case - the biosphere.

It is known that under similar conditions, ecosystems similar to each other are formed, having the same set of ecological niches, even if these ecosystems are located in different geographical areas, separated by insurmountable obstacles. The most striking example in this regard is provided by the living world of Australia, which has long developed separately from the rest of the land world. In Australian ecosystems, functional niches can be identified that are equivalent to the corresponding niches of ecosystems on other continents. These niches turn out to be occupied by those biological groups that are present in the fauna and flora of a given area, but are similarly specialized for the same functions in the ecosystem that are characteristic of a given ecological niche. Such types of organisms are called ecologically equivalent. For example, the large kangaroos of Australia are equivalent to the bison and antelopes of North America (on both continents these animals are now replaced mainly by cows and sheep).

Such phenomena in the theory of evolution are called parallelism. Very often parallelism is accompanied by convergence (convergence) of many morphological (from the Greek word morphe - form) characteristics. So, despite the fact that the whole world was conquered by plantar animals, in Australia, for some reason, almost all mammals are marsupials, with the exception of several species of animals brought much later than the living world of Australia finally took shape. However, there are also marsupial moles, marsupial squirrels, marsupial wolves, etc. here. All these animals are not only functionally, but also morphologically similar to the corresponding animals of our ecosystems, although there is no relationship between them.

All this indicates the presence of a certain “program” for the formation of ecosystems in these specific conditions. All matter can act as “genes” that store this program, each particle of which holographically stores information about the entire Universe. This information is realized in the actual world in the form of laws of nature, which contribute to the fact that various natural elements can be formed into ordered structures not at all in an arbitrary manner, but in the only possible way, or at least in several possible ways. For example, a water molecule produced from one oxygen atom and two hydrogen atoms has the same spatial shape, regardless of whether the reaction took place here or in Australia, although according to Isaac Asimov’s calculations, only one chance is realized out of 60 million. Probably something similar happens in the case of the formation of ecosystems.

Thus, in any ecosystem there is a certain set of potentially possible (virtual) ecological niches strictly linked to each other, designed to ensure the integrity and sustainability of the ecosystem. This virtual structure is a kind of “biofield” of a given ecosystem, containing a “standard” of its actual (material) structure. And by and large, it doesn’t even matter what the nature of this biofield is: electromagnetic, informational, ideal or some other. The very fact of its existence is important.

In any naturally formed ecosystem that has not experienced human impact, all ecological niches are filled. This is called the rule of mandatory filling of ecological niches. Its mechanism is based on the property of life to densely fill all the space available to it (in this case, space is understood as a hypervolume of environmental factors). One of the main conditions ensuring the implementation of this rule is the presence of sufficient species diversity.

The number of ecological niches and their interconnection are subordinated to the single goal of functioning of the ecosystem as a single whole, which has mechanisms of homeostasis (stability), binding and release of energy and circulation of substances. In fact, the subsystems of any living organism are focused on the same goals, which once again indicates the need to revise the traditional understanding of the term “living being”. Just as a living organism cannot exist normally without one or another organ, an ecosystem cannot be sustainable if all its ecological niches are not filled. Therefore, the generally accepted definition of an ecological niche given above is apparently not entirely correct. It comes from the vital status of a particular organism (reductionist approach), while the needs of the ecosystem in the implementation of its vital functions must be put in first place (holistic approach). Specific types of organisms can only fill a given ecological niche if it corresponds to their life status. In other words, life status is only a “request” for an ecological niche, but not yet the niche itself. Thus, an ecological niche should apparently be understood as a structural unit of an ecosystem, characterized by a certain function necessary to ensure the viability of the ecosystem, and which for this purpose must necessarily be filled with organisms with the corresponding morphological specialization.

Conclusion

The position of the population in the ecosystem can be different: from complete dominance (Scots pine in a pine forest) to complete dependence and subordination (light-loving grasses under the forest canopy). At the same time, on the one hand, it strives to carry out its life processes as fully as possible in its own interests, and on the other hand, it automatically ensures the life activity of other populations of the same biocenosis, being a component of the food chain, as well as through topical, adaptive and other connections.

Those. each population, as a full representative of the species in the ecosystem, has its place in it. American ecologist R. McIntosh called it an ecological niche.

Main components of ecological niches:

1. Specific habitat (physico-chemical properties of the ecotope and climatic conditions);

2. Biocenotic role (producer, consumer or destroyer of organic matter);

3. Position within one’s own trophic level (dominance, co-dominance, subordination, etc.);

4. Place in the food chain;

5. Position in the system of biotic relations.

In other words, an ecological niche is the sphere of life activity of a species in an ecosystem. Since a species is represented in an ecosystem by one population, it is obvious that it is the population that occupies a particular ecological niche in it. The species, by and large, occupies its ecological niche in the global ecosystem - the biosphere. A more complex question is whether an individual has its own ecological niche. A niche not only as a section of ecotope territory, but also as a kind of its own and unique role, determined by its ability to struggle for existence. In a number of cases, such a role cannot be identified either practically or theoretically. For example, a mosquito in a cloud of mosquitoes or a wheat plant of any variety in an agrocenosis do not differ from each other in any significant parameters. In other cases, the presence of its own ecological niche is obvious: a leader in a pack of wolves, a queen bee in a hive of bees, etc. Obviously, the more differentiated or social the community (population), the more clearly the signs of the ecological niches of each individual appear. They are most clearly differentiated and outlined in human communities: the president of a state, the head of a company, a pop star, etc. and so on.

So, in general ecology, ecological niches are considered as a reality for such taxa as a species (subspecies, variety) and population, and for individual heterogeneous communities - and for an individual. In homogeneous communities, considering the place and role of individual individuals, it is quite possible to use the term microniche.

Literature

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2. Solbrig O., Solbrig D. Population biology and evolution. - M.: Mir, 1982.
3. Mirkin B.M. What are plant communities? - M.: Nauka, 1986, pp. 38-53.
4. Mamedov N.M., Surovegina I.T. Ecology. - M.: School-Press, 1996, pp. 106-111.
5. Shilov I.A. Ecology. - M.: Higher school, 2000, pp. 389-393.

Ecological niche– the totality of all environmental factors within which the existence of a species in nature is possible. Concept ecological niche usually used when studying the relationships of ecologically similar species belonging to the same trophic level. The term “ecological niche” was proposed by J. Greenell (1917) to characterize the spatial distribution of species (i.e., the ecological niche was defined as a concept close to habitat).

Later, C. Elton (1927) defined an ecological niche as the position of a species in a community, emphasizing the special importance of trophic relationships. Back in the late 19th and early 20th centuries, many researchers noticed that two species, ecologically close and occupying a similar position in the community, could not coexist stably in the same territory. This empirical generalization was confirmed in the mathematical model of competition between two species for one food (V. Volterra) and the experimental works of G.F. Gause ( Gause's principle).

Modern concept ecological niche formed on the basis of the ecological niche model proposed by J. Hutchinson (1957, 1965). According to this model, an ecological niche can be represented as part of an imaginary multidimensional space (hypervolume), the individual dimensions of which correspond to the factors necessary for the normal existence of a species.

The divergence of ecological niches of different species through divergence occurs mostly due to their association with different habitats, different foods, and different times of use of the same habitat. Methods have been developed for assessing the width of the ecological niche and the degree of overlap of the ecological niches of different species. Liter: Giller P. Community structure and ecological niche. – M.: 1988 (according to BES, 1995).

In environmental modeling the concept ecological niche characterizes a certain part of the space (abstract) of environmental factors, a hypervolume in which none of the environmental factors goes beyond the tolerance limits of a given species (population). The set of such combinations of values of environmental factors at which the existence of a species (population) is theoretically possible is called fundamental ecological niche.

Realized ecological niche They call part of the fundamental niche, only those combinations of factor values at which the stable or prosperous existence of a species (population) is possible. Concepts sustainable or prosperous existence require the introduction of additional formal restrictions when modeling (for example, mortality should not exceed birth rate).

If, with a given combination of environmental factors, a plant can survive, but is not able to reproduce, then we can hardly talk about well-being or sustainability. Therefore, this combination of environmental factors refers to the fundamental ecological niche, but not to the realized ecological niche.

Outside the framework of mathematical modeling, of course, there is no such rigor and clarity in the definition of concepts. In modern environmental literature, four main aspects can be distinguished in the concept of an ecological niche:

1) spatial niche, including a complex of favorable environmental conditions. For example, insectivorous birds of spruce-blueberry live, feed and nest in different layers of the forest, which largely allows them to avoid competition;

2) trophic niche. It stands out especially because of the enormous importance of food as an environmental factor. The division of food niches among organisms of the same trophic level living together not only avoids competition, but also contributes to a more complete use of food resources and, therefore, increases the intensity of the biological cycle of matter.

For example, the noisy population of “bird markets” creates the impression of a complete absence of any order. In fact, each species of bird occupies a trophic niche strictly defined by its biological characteristics: some feed near the shore, others at a considerable distance, some fish near the surface, others at depth, etc.

The trophic and spatial niches of different species may partially overlap (remember: the principle of ecological duplication). Niches can be wide (non-specialized) or narrow (specialized).

3) multidimensional niche, or a niche as a hypervolume. The idea of a multidimensional ecological niche is associated with mathematical modeling. The entire set of combinations of environmental factor values is considered as a multidimensional space. In this huge set, we are only interested in such combinations of values of environmental factors under which the existence of an organism is possible - this hypervolume corresponds to the concept of a multidimensional ecological niche.

4) functional idea of an ecological niche. This idea complements the previous ones and is based on the functional similarities of a wide variety of ecological systems. For example, they talk about the ecological niche of herbivores, or small predators, or animals that feed on plankton, or burrowing animals, etc. The functional concept of the ecological niche emphasizes role organisms in an ecosystem and corresponds to the usual concept of “profession” or even “position in society.” It is in functional terms that we speak of environmental equivalents– species occupying functionally similar niches in different geographical regions.

“An organism's habitat is where it lives, or where it can usually be found. Ecological niche- a more capacious concept that includes not only the physical space occupied by a species (population), but also the functional role of this species in the community (for example, its trophic position) and its position relative to gradients of external factors - temperature, humidity, pH, soil and other conditions of existence. These three aspects of the ecological niche are conveniently referred to as the spatial niche, the trophic niche, and the multidimensional niche, or niche as hypervolume. Therefore, the ecological niche of an organism depends not only on where it lives, but also includes the total sum of its requirements for the environment.

Species that occupy similar niches in different geographic areas are called environmental equivalents"(Y. Odum, 1986).

V.D. Fedorov and T.G. Gilmanov (1980, pp. 118 – 127) note:

“The study of realized niches by describing the behavior of the well-being function at the cross section of them with straight lines and planes corresponding to some selected environmental factors is widely used in ecology (Fig. 5.1). Moreover, depending on the nature of the factors to which the particular well-being function under consideration corresponds, one can distinguish between “climatic”, “trophic”, “edaphic”, “hydrochemical” and other niches, the so-called private niches.

A positive conclusion from the analysis of private niches can be a conclusion from the opposite: if the projections of private niches onto some (especially some) of the axes do not intersect, then the niches themselves do not intersect in a space of higher dimension. ...

Logically, there are three possible options for the relative arrangement of niches of two species in the space of environmental factors: 1) separation (complete mismatch); 2) partial intersection (overlapping); 3) complete inclusion of one niche into another. ...

Niche separation is a fairly trivial case, reflecting the fact of the existence of species adapted to different environmental conditions. Cases of partial overlap of niches are of much greater interest. As mentioned above, overlapping projections even along several coordinates at once, strictly speaking, does not guarantee the actual overlapping of the multidimensional niches themselves. Nevertheless, in practical work, the presence of such intersections and data on the occurrence of species in similar conditions is often considered sufficient evidence in favor of overlapping niches of species.

To quantitatively measure the degree of overlap between niches of two species, it is natural to use the ratio of the volume of intersection of sets... to the volume of their union. ... In some special cases, it is of interest to calculate the measure of intersection of niche projections.”

TRAINING TESTS FOR TOPIC 5

The position of a species that it occupies in the general system of biocenosis, the complex of its biocenotic connections and requirements for abiotic environmental factors is called ecological niche kind.

The concept of ecological niche has proven to be very fruitful for understanding the laws of coexistence between species. Many ecologists worked on its development: J. Grinnell, C. Elton, G. Hutchinson, Y. Odum and others.

The concept of “ecological niche” should be distinguished from the concept of “habitat”. In the latter case, we mean that part of the space that is inhabited by the species and which has the necessary abiotic conditions for its existence. The ecological niche of a species depends not only on abiotic environmental conditions, but also, no less, on its biocenotic environment. The nature of the ecological niche occupied is determined both by the ecological capabilities of the species and by the extent to which these capabilities can be realized in specific biocenoses. This is a characteristic of the lifestyle that a species can lead in a given community.

G. Hutchinson put forward the concepts of a fundamental and realized ecological niche. Under fundamental refers to the entire set of conditions under which a species can successfully exist and reproduce. In natural biocenoses, however, species do not develop all the resources suitable for them due, first of all, to competitive relations. Realized ecological niche - this is the position of a species in a specific community, where it is limited by complex biocenotic relationships. In other words, the fundamental ecological niche characterizes the potential capabilities of a species, and the realized one characterizes that part of them that can be realized under given conditions, given the availability of the resource. Thus, the realized niche is always smaller than the fundamental one.

In ecology, the question of how many ecological niches a biocenosis can accommodate and how many species of any particular group that have similar environmental requirements can live together is widely discussed.

Specialization of a species in nutrition, use of space, time of activity and other conditions is characterized as a narrowing of its ecological niche, while reverse processes are characterized as its expansion. The expansion or narrowing of the ecological niche of a species in a community is greatly influenced by competitors. Competitive exclusion rule formulated by G.F. Gause for species that are similar in ecology, can be expressed in such a way that two species do not coexist in the same ecological niche.

Experiments and observations in nature show that in all cases where species cannot avoid competition for basic resources, weaker competitors are gradually driven out of the community. However, in biocenoses there are many opportunities for at least partial delimitation of the ecological niches of species that are similar in ecology.

Exit from competition is achieved due to divergence of requirements for the environment, changes in lifestyle, which, in other words, is the delimitation of the ecological niches of species. In this case, they acquire the ability to coexist in the same biocenosis. Each of the species living together is capable of more complete use of resources in the absence of a competitor. This phenomenon is easy to observe in nature. Thus, herbaceous plants in a spruce forest are able to be content with a small amount of soil nitrogen, which remains from being intercepted by tree roots. However, if the roots of these spruce trees are cut off in a limited area, the nitrogen nutrition conditions for the grasses improve and they grow rapidly, taking on a dense green color. Improving living conditions and increasing the number of a species as a result of removing from the biocenosis another, similar in environmental requirements, is called competitive release.

The division of ecological niches by co-living species with their partial overlap is one of the mechanisms of stability of natural biocenoses. If any of the species sharply reduces its numbers or drops out of the community, others take on its role. The more species there are in a biocenosis, the lower the number of each of them, the more pronounced their ecological specialization. In this case, they speak of “a denser packing of ecological niches in the biocenosis.”

Closely related species living together usually have very fine delineations of ecological niches. Thus, ungulates grazing in African savannas use pasture food in different ways: zebras pluck mainly the tops of grasses, wildebeests feed on what zebras leave for them, choosing certain types of plants, gazelles pluck the shortest grasses, and topi antelopes are content with tall dry ones. stems left behind by other herbivores. The same “division of labor” in the southern European steppes was once carried out by wild horses, marmots and gophers (Fig. 92).

Rice. 92. Different types of herbivores eat grass at different heights in African savannas (top rows) and in the Eurasian steppes (bottom rows) (according to F. R. Fuente, 1972; B. D. Abaturov, G. V. Kuznetsov, 1973)

In our winter forests, insectivorous tree-feeding birds also avoid competition with each other due to their different search patterns. For example, nuthatches and pikas collect food on tree trunks. At the same time, nuthatches quickly examine the tree, quickly grabbing insects or seeds caught in large cracks in the bark, while small pikas carefully search the surface of the trunk for the smallest cracks into which their thin awl-shaped beak penetrates. In winter, in mixed flocks, great tits conduct a wide search in trees, bushes, stumps, and often in the snow; Chickadees inspect mainly large branches; long-tailed tits search for food at the ends of branches; small kinglets carefully search the upper parts of coniferous crowns.

Ants exist in natural conditions in multi-species associations, the members of which differ in lifestyle. In the forests of the Moscow region, the following association of species is most often found: the dominant species (Formica rufa, F. aquilonia or Lasius fuliginosus) occupies several layers, L. flavus is active in the soil, Myrmica rubra is active in the forest litter, the ground layer is colonized by L. niger and F. fusca, trees – Camponotus herculeanus. Specialization for life in different tiers is reflected in the life form of species. In addition to separation in space, ants also differ in the nature of obtaining food and in the time of daily activity.

In deserts, the most developed complex of ants collect food on the soil surface (herpetobionts). Among them, representatives of three trophic groups stand out: 1) diurnal zoonecrophages - active in the hottest time, feeding on the corpses of insects and small living insects active during the day; 2) nocturnal zoophages - they hunt sedentary insects with soft covers that appear on the surface only at night, and molting arthropods; 3) carpophages (day and night) - eat plant seeds.

Several species from the same trophic group can live together. The mechanisms for exiting competition and delineating ecological niches are as follows.

1. Size differentiation (Fig. 93). For example, the average weights of working individuals of the three most common diurnal zoonecrophages in the Kyzylkum sands are in the ratio 1:8:120. Approximately the same ratio of weights is found in a medium-sized cat, lynx and tiger.

Rice. 93. Comparative sizes of four species of ants from the group of diurnal zoonecrophages in the sandy desert of the Central Karakum and distribution of prey of three species by weight class (according to G. M. Dlussky, 1981): 1 – medium and large workers of Cataglyphis setipes; 2 – S. pallida; 3 – Acantholepis semenovi; 4 – Plagiolepis pallescens

2. Behavioral differences consist of different foraging strategies. Ants that create roads and use the mobilization of carriers to carry discovered food to the nest feed primarily on the seeds of plants that form clumps. Ants, whose foragers work as solitary foragers, collect mainly seeds of plants that are dispersedly distributed.

3. Spatial differentiation. Within the same tier, food collection by different species can be confined to different areas, for example, in open areas or under wormwood bushes, on sandy or clayey areas, etc.

4. Differences in activity times relate mainly to the time of day, but in some species there are discrepancies in activity between seasons (mainly spring or autumn activity).

The ecological niches of species vary in space and time. They can be sharply differentiated in individual development depending on the stage of ontogenesis, as, for example, in caterpillars and adults of lepidoptera, larvae and May beetles, tadpoles and adult frogs. In this case, both the habitat and the entire biocenotic environment change. In other species, the ecological niches occupied by young and adult forms are closer, but nevertheless there are always differences between them. Thus, adult perches and their fry living in the same lake use different energy sources for their existence and are part of different food chains. The fry live off small plankton, while the adults are typical predators.

The weakening of interspecific competition leads to the expansion of the ecological niche of the species. On oceanic islands with a poor fauna, a number of birds, compared to their relatives on the mainland, inhabit more diverse habitats and expand the range of food, since they do not encounter competing species. Among island inhabitants, there is even increased variability in the shape of the beak as an indicator of the expansion of the nature of food connections.

If interspecific competition narrows the ecological niche of a species, preventing all its potential from being manifested, then intraspecific competition, on the contrary, contributes to the expansion of ecological niches. With an increased number of species, the use of additional food begins, the development of new habitats, and the emergence of new biocenotic connections.

In reservoirs, plants that are completely immersed in water (elodea, hornwort, urut) find themselves in different conditions of temperature, illumination, and gas conditions than those floating on the surface (telores, watercolor, duckweed) or rooting at the bottom and bringing leaves to the surface (water lily, egg capsule, Victoria). They also differ in their relationships with the environment. Epiphytes of tropical forests occupy similar, but still not identical niches, since they belong to different ecological groups in relation to light and water (heliophytes and sciophytes, hygrophytes, mesophytes and xerophytes). Different epiphytic orchids have highly specialized pollinators.

In a mature broad-leaved forest, the trees of the first tier - common oak, smooth elm, sycamore maple, heart-leaved linden, and common ash - have similar life forms. The tree canopy formed by their crowns ends up in the same horizon, under similar environmental conditions. But a careful analysis shows that they participate in the life of the community in different ways and, therefore, occupy different ecological niches. These trees differ in the degree of light and shade tolerance, timing of flowering and fruiting, methods of pollination and distribution of fruits, composition of consorts, etc. Oak, elm and ash are anemophilous plants, but the saturation of the environment with their pollen occurs at different times. Maple and linden are entomophiles, good honey plants, but they bloom at different times. Oak has zoochory, while other broad-leaved trees have anemochory. The composition of consorts is different for everyone.

If in a broad-leaved forest the tree crowns are located in the same horizon, then the active root endings are located at different depths. The roots of oak penetrate most deeply, the roots of maple are located higher and the roots of ash are even more superficial. The litter of different tree species is utilized at different rates. The leaves of linden, maple, elm, and ash almost completely decompose by spring, and the leaves of oak still form loose forest litter in the spring.

In accordance with the ideas of L. G. Ramensky about the ecological individuality of species and taking into account the fact that plant species in a community participate in the development and transformation of the environment and energy transformation in different ways, we can assume that in the existing phytocenoses each plant species has its own ecological niche .

During ontogenesis, plants, like many animals, change their ecological niche. As they age, they use and transform their environment more intensively. The transition of a plant into the generative period significantly expands the range of consorts and changes the size and intensity of the phytogenic field. The environment-forming role of aging, senile plants decreases. They are losing many consorts, but the role of the destructors associated with them is increasing. Production processes are weakened.

Rice. 94. Correlation between foliage layer diversity and bird species diversity (Shannon MacArthur indices from E. Pianka, 1981)

Bibliography

Shilov I. A. Ecology. M.: Higher School, 1997.

Khristoforova N.K. Fundamentals of ecology. Vladivostok: Dalnauka, 1999.

Gilyarov A. M. Population ecology. M.: Moscow State University Publishing House, 1990.