Give a definition ecological niche... How do you understand the term "human ecological niche"?

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An ecological niche is called the position of a species that it occupies in common system biocenosis, the complex of its biocenotic relationships and requirements for abiotic environmental factors. The ecological niche reflects the participation of the species in the biocenosis. This does not mean its territorial location, but the functional manifestation of the organism in the community. According to C. Elton (1934), an ecological niche is "a place in a living environment, the relation of a species to food and enemies." The ecological niche concept has proven to be very fruitful for understanding the laws living together species. In addition to C. Elton, many ecologists have worked on its development, among them D. Grinnell, G. Hutchinson, J. Odum, and others.

Each species or its parts (populations, groupings of various ranks) occupy a certain place in their environment. For example, a certain type of animal cannot arbitrarily change the food ration or feeding time, the place of breeding, refuge, etc. For plants, this conditionality of conditions is expressed, for example, through love of light or love of shade, a place in the vertical division of the community (confinement to a certain tier), time of the most active growing season. For example, under a forest canopy, some plants have time to complete the main life cycle, which ends with seed ripening, before the leaves of the tree canopy open up (spring ephemera). At a later time, their place is taken by other, more shade-tolerant plants. A special group of plants is capable of quickly capturing free space (pioneer plants), but has a low competitive ability and therefore quickly gives way to other (more competitive) species.

Figure 1 Ecological niches of organisms feeding on roots (1), root secretions (2), leaves (3), stem and trunk tissues (4), fruits and seeds (5, 6), flowers and pollen (7, 8), juices (9) and kidneys (10) (after I. N. Ponomareva, 1975)

These examples illustrate an ecological niche or its individual elements. An ecological niche is usually understood as the place of an organism in nature and the whole way of its life, or, as they say, life status, including the attitude to environmental factors, types of food, time and methods of feeding, breeding sites, shelters, etc. This concept is much more voluminous and meaningful than the concept of "habitat". American ecologist Odum figuratively called the habitat the “address” of the organism (species), and the ecological niche - its “profession”. As a rule, a large number of organisms live in one habitat. different types... 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. So, a similar habitat, as noted above, in the forest is occupied by elk and squirrel. But their niches are completely different: the squirrel lives mainly in the crowns of trees, feeds on seeds and fruits, reproduces in the same place, etc. The entire life cycle of an elk is associated with the sub-log space: feeding on green plants or their parts, reproduction and shelter in thickets, etc. n. If organisms occupy different ecological niches, they usually do not enter into competitive relations, the spheres of their activity and influence are separated. In this case, the relationship is considered neutral. At the same time, each ecosystem contains species that claim the same niche or its elements (food, shelter, etc.). In this case, competition is inevitable, the struggle for the possession of a niche. The evolutionary relationship has developed in such a way that species with similar requirements for the environment cannot coexist for a long time. This pattern is not without exceptions, but it is so objective that it is formulated in the form of a provision, which is called the "rule of competitive exclusion." The author of this rule is ecologist GF Gause. It sounds like this: if two species with similar requirements for the environment (nutrition, behavior, breeding sites, etc.) enter into a competitive relationship, then one of them must die or change its lifestyle and occupy a new ecological niche. Sometimes, for example, in order to remove acute competitive relations, it is enough for one organism (animal) to change the feeding time without changing the type of food itself (if competition arises on the kidney of food relations), or to find a new habitat (if competition takes place on the basis of this factor) and etc.

Of the other properties of ecological niches, we note that an organism (species) can change them throughout its life cycle... The most striking example in this regard is insects. So, the ecological niche of larvae May beetle associated with soil, nutrition by root systems of plants. At the same time, the ecological niche of beetles is associated with the terrestrial environment, feeding on green parts of plants.

The life forms of organisms are largely associated with ecological niches. The latter include groups of species that are often systematically far apart, but have developed the same morphological adaptations as a result of existence in similar conditions. For example, dolphins (mammals) and predatory fish actively moving in the aquatic environment are characterized by the similarity of life forms. In steppe conditions, jerboas and kangaroos (jumpers) are represented by similar life forms. In the plant world, separate life forms are represented by numerous tree species occupying the upper tier as a thread, shrubs that exist under the forest canopy, and grasses in the ground cover.

Unlimited ecological niche, allowed him to move to the rank unique look, capable of subjugating other species to their interests, destroying them. Such phenomena are alien to species that exist within the boundaries of ecosystems and occupy certain places in food chains, since the destruction of other species is tantamount to self-destruction. This is one of the paradoxes of human development as a biosocial being. Man ensured his transformation into a hypereubiont not due to biochogic mechanisms, but due to technical means, and therefore it has largely lost its biological adaptation potential. This is the reason that a person is among the first candidates to leave the arena of life as a result of environmental changes caused by him.

When studying animal behavior in the wild, it is important to understand the impact of the consequences of behavior on an animal's ability to survive. The consequences of a particular type of activity depend mainly on the immediate conditions of the animal's habitat. In the conditions to which the animal is well adapted, the consequences of this or that type of activity can be beneficial. The same activity carried out under different conditions can be harmful. To understand how animal behavior has evolved, we need to understand how animals adapt to their environment.

Ecology - is a branch of natural science that studies the relationship of animals and plants with their environment natural environment... It relates to all aspects of these relationships, including energy flows through ecosystems, animal and plant physiology, animal population structure and behavior, etc. In addition to gaining accurate knowledge about specific animals, the ecologist seeks to understand general principles environmental organization, and here we look at some of them.

In the process of evolution, animals adapt to specific conditions environment, or habitat. Habitats are usually characterized by describing their physical and chemical characteristics. The type of plant communities depends on physical properties environments such as soil and climate. Plant communities provide a variety of possible habitats for animals to use. The association of plants and animals, together with the specific conditions of natural habitat, forms an ecosystem. There are 10 main types of ecosystems on the globe, called biomes. In fig. 5.8 shows the distribution of the world's major terrestrial biomes. There are also marine and freshwater biomes. For example, a biome like the savannah covers large areas of Africa, South America and Australia and is grassy plains with sparse trees in tropical and subtropical areas. the globe... The rainy season is typical for savannas. At the upper end of the rainfall distribution range, savannah is gradually replaced by tropical forests, and at the lower end by deserts. The African savannah is dominated by acacias, the South American savannah is dominated by palms, and the Australian savannah is dominated by eucalyptus trees. A characteristic feature of the African savanna is a wide variety of herbivorous ungulates, which provide a variety of predators. V South America and Australia, the same niches are occupied by other species.

The collection of animals and plants that inhabit a particular habitat is called a community. The species that form a community are divided into producers, consumers and decomposers. Producers are green plants that capture solar energy and turn it into a chemical one. Consumables are animals that eat plants or herbivores and thus indirectly depend on plants for energy. Reducers are usually fungi and bacteria that decompose dead animal and plant residues into substances that can be used again by plants.

Niche - it is the role of an animal in a community, determined by its interrelationships both with other organisms and with the physical environment. So, herbivores usually feed on plants, and herbivores, in turn, are eaten by predators. The species that occupy this niche are different in different parts of the world. For example, rabbits and hares occupy the niche of small herbivores in temperate zones in the Northern Hemisphere, agouti and whiskashi in South America, hyraxes and white-legged hamsters in Africa, and wallabies in Australia.

Rice. 5.8. Distribution of the main land biomes of the world.

In 1917, the American ecologist Grinnell pioneered the niche theory based on a study of the California mockingbird (Toxostoma redivivum) - a bird that nests in dense foliage at a height of one to two meters above the ground. The location of the nest is one of the characteristics that can be used to describe the niche of an animal. In mountainous areas, the vegetation necessary for nesting is available only in an ecological community called chaparral. The habitat of the mockingbird, as described by the physical characteristics of the environment, is also determined in part by the reaction of the mockingbird population to the situation in the niche. So, if the height of the nest above the ground is a decisive factor in saving from predators, then there will be strong competition in the population for nest sites on optimal height... If this factor was not so decisive, then more individuals could build nests elsewhere. The living conditions in this niche are also influenced by competition from other species for nesting sites, food, etc. The habitat of the California mockingbird is determined in part by the situation with the niches, the distribution of other shrub species characteristic of the chaparral, and the population density of the mockingbird itself. It is clear that if its density is low, birds nest only in best locations and this affects the habitat of the species. Thus, the overall relationship of the mockingbird with habitat conditions, which is often denoted by the term ecotope, are the result of complex interactions of niche, habitat and population characteristics.

If animals of different species use the same resources, are characterized by some common preferences or limits of stability, then we are talking about overlapping niches (Figure 5.9). Overlapping niches leads to competition, especially when resources are scarce. Competitive exclusion principle states that two species with the same niches cannot exist in the same place at the same time with limited resources. It follows from this that if two species coexist, then there must be ecological differences between them.

Rice. 5.9. Overlapping niches. The fitness of an animal can often be represented as a bell-shaped curve along a gradient in the environment, such as, for example, temperature. Overlapping of niches (shaded area) occurs in the part of the gradient occupied by representatives of different species.

As an example, consider the relationship of niches in a group of leaf-picking bird species that feed on oak trees on a mountainous coastline in central California (Root, 1967). This group, called guild, constitute species that use the same natural resources in the same way. The niches of these species overlap to a large extent, and therefore they compete with each other. The advantage of the guild concept is that in this case all the competing species of a given site are analyzed, regardless of their taxonomic position. If we consider the diet of this guild of birds as an element of their habitat, then it should be said that most of this diet should consist of arthropods collected from the leaves. This is an arbitrary classification as any species can be a member of more than one guild. For example, the plain tit (Parus inornatus) Belongs to a leaf-picking bird guild based on its foraging behavior; in addition, she is also a member of the hollow bird guild due to nesting requirements.

Rice. 5.11. The three types of foraging behavior in leaf-picking birds are represented as three sides of a triangle. The length of the line perpendicular to the side of the triangle is proportional to the amount of time it took for this behavior. The sum of all three lines for each type is equal to 100%. (By Root, 1967.)

Although in this case five species of birds feed on insects, each species catches insects that differ in size and taxonomic position. The taxonomic categories of insects eaten by these five species overlap, but each species is specialized in a particular taxon. The sizes of the victims completely overlap, but their mean values ​​and variances are different, at least in some cases. Root (1967) also found that birds of these species have three types of foraging behavior:

1) picking up insects from the surface of the leaves when the bird moves on a hard substrate;

2) collecting insects from the surface of the leaves by a hovering bird;

3) catching flying insects.

The fraction of the time that each species spends on a particular method of obtaining food is shown in Fig. 5.11. This example clearly demonstrates the process of ecological specialization in behavior. The behavior of each species influences the behavior of other species in such a way that the members of this guild develop all possible types of food-gathering behavior and use all types of prey.

Competition often leads to the dominance of one species; this is expressed in the fact that dominant species have an advantage in the use of resources such as food, space and shelter (Miller, 1967; Morse, 1971). On the basis of theory, one would expect that a species that becomes subordinate to another species would change resource use in such a way as to reduce overlap with the dominant species. Usually, this subordinate view reduces the use of some resources, thus reducing the width of the niche. In some cases, a subordinate species can expand a niche to include previously unused resources, either by subordinating other species in adjacent niches, or by making fuller use of the fundamental niche.

If a subordinate species survives in competition with the dominant species, then its main niche is wider than that of the dominant species. Such cases were noted in bees and blackbirds of the new world (Orians and Willson, 1964). Since the priority in the use of resources belongs to the dominant species, subordinate species can be excluded from the niche space when resources are limited, their number is unpredictable, and the search for food requires significant effort; and all this significantly reduces the fitness of the subordinate species in the area of ​​overlap. In such cases, the subordinate species can be expected to be subject to significant selection pressures and change their fundamental niches, either through specialization or by developing resistance to a wider range. physical conditions habitat.

Adaptability of animal behavior

Naturalists and ethologists have found numerous examples of the amazing ways in which animals are perfectly adapted to the conditions of their environment. The difficulty in explaining this kind of animal behavior is that it seems convincing only because the various details and observations fit together too well; in other words, good story may seem compelling simply because it's a good story. This does not mean that a good story cannot be true. In any correct explanation of behavioral adaptation, the various details and observations must indeed fit together. The problem is that biologists, like scientists, must evaluate data, and good description- not always good data. As in a court of law, the data must be more than detailed and must contain some elements of independent confirmation.

One way to obtain evidence of behavioral adaptability is to compare related species that occupy different habitats. Classic example This approach is the work of Ester Cullen (1957) comparing the nesting characteristics of kittiwakes nesting on rocks (Rissa tridactyla) and ground-nesting gulls such as the common (Lams ridibundus) and silvery (Lams argentatus). Kittiwakes nest on rocky ledges, inaccessible to predators, and, apparently, evolved from gulls nesting on the ground as a result of pressure from predators. Kittiwakes have inherited some of the features of ground nesting gulls, such as partially camouflaging their eggs. The eggs of birds nesting on the ground are usually well camouflaged for protection from predators, but in kittiwakes the color of the eggs cannot fulfill this function, since each nest is marked with conspicuous white droppings. Adult and juvenile gulls nesting on the ground are neat and avoid defecation near the nest so as not to reveal its location. Thus, it seems most likely that the camouflage color of kittiwake eggs is evidence that their ancestors nested on the ground.

Cullen (1957) studied a breeding colony of kittiwakes in the Farne Islands off the east coast of the United Kingdom, where they breed on very narrow rock ledges. She found that their eggs were not attacked by land animals, such as rats, or birds, such as herring gulls, which often prey on the eggs of birds that nest on the ground. Kittiwakes feed mainly on fish and do not devour eggs and chicks from neighboring nests, as gulls nesting on the ground often do. Kittiwakes, apparently, have already lost most of the adaptations that protect other gulls from predators. For example, they not only do not camouflage the nest, but they also rarely emit cries of alarm and do not attack predators all together.

Rice. 5.12. Red-footed talkers (Rissa brevirostris), nesting on the rocky outcrops of the Pribylov Islands in the Bering Sea

Kittiwakes have many special adaptations for nesting on rocks. They have a light body and strong fingers and claws that allow them to cling to ledges too small for other gulls. Compared to ground-nesting gulls, adult kittiwakes have a number of behavioral adaptations to their rocky habitat. Their behavior during fighting is limited by the strict framework of the stereotype in comparison with relatives nesting on the ground (Fig. 5.12). They build fairly elaborate bowl-shaped nests using twigs and silt, while land-nesting seagulls build rudimentary nests from grass or seaweed without using silt as cement. Kittiwake chicks differ from chicks of other gulls in many ways. For example, they stay in the nest for a longer period and spend most of their time with their heads turned toward the rock. They snatch the regurgitated food straight from the throat of their parents, while most gulls pick it up from the ground, where it is thrown by adults. When frightened, nestlings of gulls nesting on the ground run away and hide, while young kittiwakes remain in the nest. Chicks of gulls are characterized by cryptic coloration and behavior, whereas chicks of kittiwakes do not.

Comparison of species can shed light on the functional significance of a particular type of behavior in the following ways: when a type of behavior is observed in one species, but not observed in another, this may be due to differences in the way natural selection acts on these two species. For example, herring gulls remove the eggshell near the nest in order to maintain the camouflage of the nest, since the inner white surface of the eggshell is clearly visible. Evidence supporting this hypothesis comes from observations of kittiwakes that do not remove their shells. As we have already seen, predators do not attack kittiwake nests and their nests and eggs are not camouflaged. If the removal of the eggshell is mainly to maintain the camouflage of the nest, then we are unlikely to find it in kittiwakes. However, if it serves other purposes, such as preventing disease, then this behavior can be expected to be observed in kittiwakes. Kittiwakes usually keep the nest very clean and throw any foreign objects out of it. Herring gulls usually do not.

The data above will be further reinforced if we can show that similar adaptations appear in other related species under the same selection pressures. One such example is given by Hailman (1965), who studied the cliff-nesting Fork-tailed Gull (Lams furcatus) in the Galapagos Islands. Heilman studied different kinds behaviors that are determined by the ability to prevent the danger of falling off the rocks. Fork-tailed gulls nest not on such steep rocks as kittiwakes, and not so high above the ground. Thus, one would expect that the corresponding adaptations of the fork-tailed gulls would be intermediate between the adaptations of kittiwakes and typical ground-nesting gulls. Fork-tailed gulls are more likely to be attacked by predators than kittiwakes, and Heilman found some behavioral traits that seem to be determined by this difference. For example, as mentioned above, kittiwake chicks defecate on the edge of the nest, thus making it very visible. Fork-tailed gull chicks defecate beyond the edge of this edge. He found that according to a number of features also associated with the intensity of predation, the fork-tailed gulls occupy an intermediate position between kittiwakes and other gulls. Thus, Heilman evaluated those behavioral traits of the Fork-tailed gulls that are adaptations to the availability of nesting space and the availability of nesting sites and nesting material. He then decided to evaluate the evidence on which Cullen (1957) hypothesized that kittiwakes' traits are the result of selection pressure that accompanies rock nesting. He selected 30 traits of the Fork-tailed Gull and divided them into three groups, depending on the degree of similarity with the behavior of kittiwakes. Taken as a whole, this comparison supports Cullen's hypothesis that the special traits of kittiwakes are the result of selection that accompanies nesting on rocks.

Crook's (1964) work on nearly 90 species of weavers (Ploceinae) is another example of this comparative approach. These small birds are found throughout Asia and Africa. Despite the external similarity, different types of weavers differ markedly in terms of social organization. Some of them protect large territory, on which camouflaged nests are built, while others nest in colonies in which the nests are clearly visible. Crook discovered that species living in forests lead a solitary lifestyle, feed on insects, and camouflage nests in a large protected area. They are monogamous, sexual dimorphism is weak. Savannah species are usually seed-eating, live in groups, and nest colonially. They are polygamous, with males being brightly colored and females dull.

Crook believed that since food in the forest is difficult to find, it is necessary that both parents feed the chicks, and for this, the parents must stick together throughout the breeding season. The density of insects that forest birds feed on is low, so a pair of birds must protect a large area to ensure an adequate supply of food for the chicks. The nests are well camouflaged, and the adult birds are dull in color, so that during their visit to the nest, predators cannot reveal its location.

In the savannah, seeds may be abundant in some places and few in others, which is an example of a patchy distribution of food. Finding food under these conditions is more effective if the birds form groups to search over a wide area. Nesting sites protected from predators are rare in the savannah, so many birds nest on the same tree. The nests are bulky to provide protection from the heat of the sun, so colonies are clearly visible. For protection from predators, nests are usually built high on thorny acacias or other similar trees (Figure 5.13). The female herself is able to feed the offspring, since there is relatively much food. The male almost does not participate in this and looks after other females. Males compete for nesting sites within the colony, and those who succeed can each attract several females, while other males remain single. In the colonial settlement of weavers (Textor cucullatus), for example, males steal nesting material from each other. Therefore, they are forced to constantly be near the nest in order to protect it. To attract females, the male makes a complex "show", hanging from the nest. If the male is successful in courtship, the female enters the nest. Such attention to the nest is typical of colonial weavers. The courtship ritual is completely different for species of birds living in the forest, in which the male chooses a female, looks after her at a noticeable distance from the nest, and then leads to the nest.

Rice. 5.13. Colony of weavers Ploceus cucullatus. Please note that big number nests are relatively inaccessible to predators. (Photo by Nicholas Collias.)

The comparative approach has proven to be a fruitful method in studying the relationship between behavior and ecology. This method was used to study birds (Lack, 1968), ungulates (Jarman, 1974), and primates (Crook, Gartlan, 1966; Glutton-Brock, Harvey, 1977). Some authors (Clutton-Brock, Harvey, 1977; Krebs, Davies, 1981) criticize the comparative approach, however, it provides satisfactory data on evolutionary aspects of behavior, provided that appropriate measures are taken to avoid substitution of concepts and self-enclosing evidence. Hailman (1965) considers the comparative method appropriate only in cases where comparison of two animal populations allows conclusions to be drawn about a third population that has not yet been studied by the time these conclusions are formulated. In this case, the hypothesis formulated as a result of the comparative study can be tested independently without using the data obtained as a result of this study. It is easy to understand that if interrelated differences in behavior and ecology exist between two populations, then this is not enough to say that these traits reflect the selection pressure arising from differences in the living conditions of these two populations. Differences resulting from confusion of variables or from comparisons of irrelevant taxonomic levels can be avoided by careful statistical analysis(Clutton-Brock, Harvey, 1979; Krebs, Davies, 1981).

Ecology abstract

Any species is adapted to certain environmental conditions (factors). If the parameters of at least one of the many factors go beyond the tolerance of the organism, it causes its oppression. The requirements of an organism to the composition and parameters of environmental factors inherited from ancestors determine the boundaries of the distribution of the species to which this organism belongs, that is, the range, and within the range - specific habitats.

In other words, any kind of animal, plant, microorganism is able to normally inhabit, feed, reproduce only in the place where it was "prescribed" by evolution for many millennia, starting with its ancestors. To designate this phenomenon, biologists borrowed the architectural term "niche". Thus, each type of living organism occupies in nature its own, inherent only ecological niche.

Ecological niche - this is the place of an organism in nature and the whole way of its life activity, or, as they say, life status, including relations to environmental factors, types of food, time and methods of feeding, breeding places, shelters, etc. This concept is much more voluminous and meaningful than the concept of "habitat".

Habitat Is a spatially limited set of conditions of the abiotic and biotic environment, which provides the entire development cycle of the organism.

American ecologist Y. Odum figuratively called the habitat the “address” of the organism, and the ecological niche - its “profession”. As a rule, 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 organisms, but each of them has its own ecological niche. Ecological niche - the functional role of a species in the place of its "registration". On the one hand, the organism is a participant in the general flow of life in the environment, and on the other hand, it is the creator of such a flow. And this, indeed, is very similar to the profession of a person.

First of all, an ecological niche cannot be occupied by two or more species, just as there are no two absolutely identical professions. The species occupies an ecological niche in order to perform a unique function only in its own way, thus mastering the habitat and at the same time shaping it. Nature is very economical - even only two species occupying the same ecological niche cannot coexist sustainably, since as a result of competition one of them will be crowded out by the other. This pattern is not without exceptions, but it is so objective that it is formulated in the form of a provision, which is called the "principle of competitive exclusion" (the principle of GF Gause): if two species with similar requirements for the environment (nutrition, behavior, breeding sites, etc.) enter into a competitive relationship, then one of them must die or change its lifestyle and occupy a new ecological niche ... Sometimes, for example, in order to remove acute competitive relations, it is enough for one organism (animal) to change the feeding time without changing the type of food itself (if competition arises on the basis of food relations), or to find a new habitat (if competition takes place on the basis of this factor) and etc. If organisms occupy different ecological niches, they usually do not enter into a competitive relationship, their spheres of activity and influence are separate. In this case, the relationship is considered neutral.

An ecological niche as a functional place of a species in the system of life cannot be empty for a long time, - this is evidenced by the rule of obligatory filling of ecological niches: an empty ecological niche is always naturally filled .

Of the other properties of ecological niches, we note that an organism (species) can change them throughout its life cycle. The most striking example in this regard is insects. Thus, the ecological niche of the May beetle larvae is associated with the soil, feeding on the root systems of plants. At the same time, the ecological niche of beetles is associated with the terrestrial environment, feeding on green parts of plants.

Communities of living organisms are formed according to the principle of filling ecological niches. In a naturally formed community, usually all niches are occupied. It is in such communities, for example, in long-lived (indigenous) forests, that the probability of the introduction of new species is very low. At the same time, it should be borne in mind that the employment of ecological niches is to a certain extent a relative concept. All niches are usually occupied by those organisms that are typical for a given region. But if an organism comes from outside (for example, seeds are brought in) accidentally or intentionally, then it can find a free niche for itself due to the fact that there were no applicants from the set existing species... In this case, a rapid increase in the number (outbreak) of an alien species is usually inevitable, since it finds extremely favorable conditions (a free niche) and, in particular, has no enemies.

An ecological niche as a functional place of a species in its habitat allows a form capable of developing new adaptations to fill this niche, but sometimes this takes a significant amount of time. Often empty ecological niches that seem to a specialist are just a hoax. Therefore, a person should be extremely careful with conclusions about the possibility of filling these niches by acclimatization. Acclimatization is a set of measures aimed at introducing a species into new habitats, carried out in order to enrich natural or artificial communities with organisms useful to humans. The heyday of acclimatization fell on the 20-40s of the twentieth century. However, over time, it became obvious that either the experiments were unsuccessful, or, worse, brought very negative results - the species were made pests, spread dangerous diseases etc. It could not be otherwise: new species placed in a foreign environment with an actually occupied ecological niche crowded out those who had already performed similar work. New species did not meet the needs of the ecosystem, sometimes they did not have enemies and therefore could multiply rapidly. But then limiting factors came into play. The number of the species fell sharply or, on the contrary, it multiplied intensively, like a rabbit in Australia and became a pest.

Ecological niche- a set of all environmental factors within which the existence of a species in nature is possible. Concept ecological niche usually used in the study of the relationship of ecologically close species belonging to the same trophic level. The term "ecological niche" was proposed by J. Grinell (1917) to characterize the spatial distribution of species (that is, an ecological niche was defined as a concept close to habitat).

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

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

The divergence of ecological niches of different species by means of divergence occurs mostly due to confinement to different habitats, different food and different times of use of the same habitat. Methods for assessing the width of the ecological niche and the degree of overlapping of ecological niches of various types have been developed. 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 of (abstract) environmental factors, a hypervolume in which none of the environmental factors goes beyond the tolerance of a given species (population). The set of such combinations of the values ​​of environmental factors for which the existence of a species (population) is theoretically possible is called fundamental ecological niche.

Realized ecological niche they call a part of the fundamental niche, only those combinations of the values ​​of factors for which a stable or prosperous existence of a species (population) is possible. Concepts sustainable or prosperous existence requires the introduction of additional formal constraints in modeling (for example, mortality should not exceed fertility).

If, with a given combination of values ​​of environmental factors, a plant can survive, but is not able to reproduce, then one can hardly speak of well-being or sustainability. Consequently, this combination of environmental factors belongs 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 ecological literature, four main aspects can be distinguished in the concept of an ecological niche:

1) spatial niche, including a set of favorable environmental conditions. For example, insectivorous birds of the blueberry-spruce forest live, feed and nest in various 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 in organisms of the same trophic level, living together, allows not only to avoid 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 colonies" creates the impression of a complete absence of any order. In fact, each bird species occupies a trophic niche strictly defined by its biological characteristics: some feed near the coast, others at a considerable distance, some fish near the surface, others at depth, etc.

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

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

4) functional idea of ​​the ecological niche. This view complements the previous ones and is based on the functional similarity of the most diverse 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 the ecosystem and corresponds to the usual concept of "profession" or even "position in society." Exactly at functionally talk about environmental equivalents- species that occupy functionally similar niches in different geographic regions.

“The habitat of an organism is the place where it lives, or the place where it can usually be found. Ecological niche- a more capacious concept, which 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 external factors- temperature, humidity, pH, soil and other conditions of existence. These three aspects of an ecological niche are conveniently designated as a spatial niche, a trophic niche, and a multidimensional niche, or a niche as a hypervolume. Consequently, the ecological niche of an organism depends not only on where it lives, but also includes the total amount of its requirements for the environment.

Species that occupy the same niches in different geographic areas are called ecological equivalents"(Yu. 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 on the cross-section of their 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 considered private function well-being, one can distinguish between the niches "climatic", "trophic", "edaphic", "hydrochemical" and others, the so-called private niches.

A positive conclusion from the analysis of private niches can be a contradictory conclusion: 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 greater dimension. ...

Three variants of the mutual arrangement of niches of two types in the space of ecological factors are logically possible: 1) separation (complete non-coincidence); 2) partial intersection (overlapping); 3) full inclusion of one niche in another. ...

The division of niches is a rather trivial case, reflecting the fact of the existence of species adapted to various ecological conditions. Cases of partial intersection of niches are of much greater interest. As mentioned above, the overlapping of projections even in several coordinates at once, strictly speaking, does not guarantee the actual overlap of the multidimensional niches themselves. However, in practical work the presence of such intersections and data on the occurrence of species in similar conditions are often considered sufficient arguments in favor of overlapping species niches.

To quantitatively measure the degree of overlapping of niches of two types, it is natural to use the value of 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 projections of niches. "

LEARNING TESTS FOR TOPIC 5

Ecological niche - the place of the species in the biogeocenosis, determined by its biotic potential and a combination of factors external environment to which he is adapted. It is not only the physical space occupied by the body, but also its functional role in the community (position in the food chain), and its place in relation to external factors.

There are 3 components in the structure of the ecological niche:

1. Spatial niche (habitat) - the "address" of the organism;
2. Trophic niche - characteristic features of nutrition and the role of the species in the community - "profession";
3. Multidimensional (hyperspace) ecological niche - the range of all conditions under which an individual or population lives and reproduces itself.

Distinguish fundamental (potential) niche, which an organism or a species could occupy in the absence of competition, predators, in which the abiotic conditions are optimal; and niche realized- the actual range of conditions for the existence of an organism, which is less than or equal to the fundamental niche.

The rule of compulsory filling of the ecological niche.
An empty ecological niche is always and necessarily naturally filled. In saturated biogeocenoses, vital resources are used most fully - in them all ecological niches are occupied. In unsaturated biogeocenoses, vital resources are partially utilized; they are characterized by the presence of free ecological niches.

Environmental duplication- occupation of the vacated ecological niche by another species capable of performing the same functions in the community as the extinct species. It follows from this that knowing the distribution of species by ecological niche in a community and the parameters of each ecological niche, it is possible to describe in advance the species that will be able to occupy this or that niche if it is released.

Environmental diversification- the phenomenon of division of the ecological niche as a result of interspecific competition. It is carried out according to three parameters:
- by spatial arrangement
- according to the diet
- by the distribution of activity in time.
As a result of diversification, a shift in characters occurs - individuals of two closely related species are more similar to each other in those parts of the ranges where they are found separately than in areas of cohabitation.

Ecological niche characteristics:
1. Width
2. Overlapping of this niche with neighboring

Ecological niche width- a relative parameter that is estimated by comparison with the width of the ecological niche of other species. Eurybionts usually have broader ecological niches than stenobionts. However, the same ecological niche can have different widths in different directions: for example, in spatial distribution, food connections, etc.

Overlapping the ecological niche occurs when different species share the same resources when living together. Overlapping can be complete or partial, according to one or several parameters of the ecological niche.

If the ecological niches of organisms of two species are very different from each other, then these species, which have the same habitat, do not compete with each other (Fig. 3).

If ecological niches partially overlap (Fig. 2), then their joint coexistence will be possible due to the presence of specific adaptations for each type.

If the ecological niche of one species includes the ecological niche of another (Fig. 1), then intense competition arises, the dominant competitor will push its rival to the periphery of the fitness zone.

Competition has important environmental consequences. In nature, individuals of each species are simultaneously subjected to interspecific and intraspecific competition. Interspecific in its consequences is opposite to intraspecific, since it narrows the area of ​​habitats and the quantity and quality of the necessary environmental resources.

Intraspecific competition promotes the territorial distribution of species, that is, the expansion of the spatial ecological niche. The end result is the ratio of interspecific and intraspecific competition. If the interspecific competition is greater, then the range of this species decreases to an area with optimal conditions and at the same time the specialization of the species increases.