Functional understanding of ecological niche

Remark 1

Ecological niche theory serves as the basis for many areas of ecological and evolutionary-ecological research, especially those related to the biotic relationships of organisms.

The concept of a niche acquired a modern look relatively recently. Apparently, R. Johnson was the first to use this term at the very beginning of the 20th century. The works of ecologists in the first half of the last century began to identify the ecological niche with the position of organisms in the community. Since the middle of the last century, the concept of a niche has become central to evolutionary ecological research.

Remark 2

One of the first developed concepts of a niche was the concept of E. Grinnell, in relation to which it is usually believed that the concept of a niche was largely identified with the concept of a habitat.

However, Grinnell actually understood a niche as an interconnected set of adaptations of organisms to the conditions of existence in a particular habitat.

Among these adaptations, he gave priority to trophic ones, i.e. food composition and foraging method, and considered the foraging behavior as the leading adaptive trait, which affects the choice of food substrates or microhabitats by animals, which, as a result, determines the biotopic preferences and range of species, their morphology and food composition.

Thus, E. Grinnell understood a niche as a property of a species, and not its environment, as a historically determined position of a species in ecosystems, which is expressed in the acquisition of a certain food specialization, spatial relationships, i.e. in all forms of manifestation of life.

A similar concept was developed by C. Elton, who used the concept of a niche to determine the position and interspecific relationships of living organisms in a community. Thus, at the dawn of the formation of the concept of a niche, it included a predominantly functional aspect.

Study of individual niche parameters

Starting from the middle of the XX$ century, the interest of ecologists has shifted to the study of individual niche parameters. These studies were based on Hutchinson's concept of a multidimensional ecological niche. According to this concept, a niche can be defined as the sum of the entire variety of resources needed for a population of a species.

Hutchinson compared a niche to a multidimensional space, or hypervolume, within which the prevailing conditions allow the organism to live indefinitely. The gradient line of each of the factors represents a certain dimension of space. The total set of values ​​of all factors under which a given organism can exist, Hutchinson called fundamental niche. Such a niche is the largest abstract hypervolume, in the absence of restrictions from competition with other species and with an optimum abiotic environment. The actual range of conditions in which an organism actually exists, less than or equal to the fundamental niche, is called the realized niche.

Remark 3

A multidimensional niche could be described using quantitative indicators and mathematical calculations could be made with it. It included both the properties of the organisms themselves and the features of their relationships in the community, so the characteristics of the niche of the species turned out to be widely variable.

Along with the presence of free niches, which can, under certain conditions, be occupied by the species most preadapted to this, Hutchinson pointed out the possibility of changing the configuration of niches and dividing once single niches into several in the process of speciation.

Further development of this concept was determined by the works of R. MacArthur, his followers and colleagues. In these studies, formalized methods have been developed for studying the degree of mutual overlap and niche width of individual species. Subsequently, many researchers began to point out the need for a differentiated approach to the study of various aspects of the niche.

Gradually, as the most important parameters of a niche, they began to name:

• habitat,
• food composition,
• time.

At the beginning of the $XXI$ century, feeding behavior began to be added to the main indicators of the ecological niche. Based on a comparative analysis of the main indicators of a niche, we came to the conclusion that they are hierarchically interconnected.

Further research in this direction contributed to the creation of the concept of a one-dimensional hierarchical ecological niche.

The basis for its creation was the ideas of Grinnell, who assumed the leading role of foraging behavior in the ecological segregation of closely related species and the hierarchical structure of their niches.

Within the framework of this concept, a niche is understood as an integral functional unit. It is defined as a system whose emergent properties follow from the specific function of each species in the ecosystem and are clearly expressed in the species-specific method of feeding behavior of the species. To do this, organisms form special adaptive features related to its ecology, morphology, physiology, genetics, etc.

Feeding behavior is stable and the most stereotypical among the indicators of the species, and determines the choice of characteristic microhabitats by animals, which further determines their biotopic and geographical distribution, affects the composition of feed, features of social organization, etc. At the same time, it itself turns out to be a systemic trait that determines the development of all other traits of a given species, is their integral expression, and holistically reflects the specifics of the niche of the species.

Any living organism is adapted (adapted) to certain environmental conditions. Changing its parameters, their going beyond certain boundaries suppresses the vital activity of organisms and can cause their death. The requirements of this or that organism to the ecological factors of the environment determine the range (limits of distribution) of the species to which the organism belongs, and within the range - specific habitats.

An ecological niche is a set

All requirements of the body to the conditions of the environment (composition and regimes of environmental factors) and the place where these requirements are met;

The whole set of biological characteristics and physical parameters of the environment that determine the conditions for the existence of a particular species, its transformation of energy, the exchange of information with the environment and their own kind.

Thus, the ecological niche characterizes the degree of biological specialization of a species. It can be argued that the habitat of an organism is its “address”, while the ecological niche is its “occupation”, or “lifestyle”, or “profession”.

The ecological specificity of species is emphasized by the axiom of ecological adaptability:

each species is adapted to a strictly defined, specific set of conditions for its existence - an ecological niche.

Since the species of organisms are ecologically individual, they also have specific ecological niches.

Thus, how many species on Earth - the same number of ecological niches.

Organisms that lead a similar way of life, as a rule, do not live in the same places due to interspecific competition.

In nature, the rule of obligatory filling of ecological niches also applies:

The empty ecological niche will always and will definitely be filled.

Human ecological niche

Man is one of the representatives of the animal kingdom, a biological species of the class of mammals. Despite the fact that it has many specific properties, it has not lost its biological essence and all the laws of ecology are valid for it to the same extent as for other organisms.

A person has his own, unique to him, ecological niche, i.e. a set of requirements for a variety of environmental factors, developed in the process of evolution. The space in which the human niche is localized is very limited. As a biological species, a person can only live within the land of the equatorial belt (tropics, subtropics). Vertically, the niche extends approximately 3.0-3.5 km above sea level.

Due to its specific properties, man has expanded the boundaries of his initial range, settled in high, middle and low latitudes, mastering the depths of the ocean and outer space. However, its fundamental ecological niche remained virtually unchanged. Outside the original range, he can survive, overcoming the resistance of limiting factors, not through adaptations, but with the help of specially created protective devices and devices.

In the conditions of industrial enterprises, many factors (noise, vibration, temperature, electromagnetic fields, impurities of a number of substances in the air, etc.) are periodically or permanently beyond the tolerance of the human body. This negatively affects him: so-called occupational diseases, periodic stresses may occur.

Human production and economic activity, the use and processing of natural resources inevitably leads to the formation of by-products that are dispersed in the environment. Chemical compounds entering the water, soil, atmosphere, and food are environmental factors and, consequently, elements of the ecological niche. In relation to them, the resistance of the human body is low, and such substances turn out to be limiting factors that destroy its niche.

Nature (environment) protection consists in a system of measures to preserve the ecological niches of living organisms, including humans.

When studying the behavior of animals in natural settings, it is important to understand the impact of the consequences of behavior on the ability of an animal to survive. The consequences of a particular type of activity depend mainly on the immediate living conditions of animals. In 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 in other conditions can be harmful. To understand how animal behavior has evolved, we need to understand how animals adapt to their environment.

Ecology - This is a branch of natural science that studies the relationship of animals and plants with their natural environment. It is relevant to all aspects of these relationships, including the flow of energy through ecosystems, the physiology of animals and plants, the structure of animal populations and their behavior, and so on. In addition to obtaining precise knowledge about specific animals, the ecologist seeks to understand the general principles of ecological organization, and here we will consider some of them.

In the process of evolution, animals adapt to specific environmental conditions, or habitats. Habitats are usually characterized by describing their physical and chemical features. The type of plant communities depends on the physical properties of the environment, such as soil and climate. Plant communities provide a variety of possible habitats that are used by animals. The association of plants and animals, together with the specific conditions of the natural habitat, forms an ecosystem. On the globe, there are 10 main types of ecosystems called biomes. On fig. 5.8 shows the distribution of the main terrestrial biomes of the world. There are also marine and freshwater biomes. For example, the savannah biome covers large areas of Africa, South America, and Australia and is grassy plains with sparse trees growing on them in the tropical and subtropical regions of the globe. Savannahs typically have a rainy season. At the upper end of the rainfall distribution range, the savanna gradually gives way to tropical forests, and at the lower end to deserts. Acacias predominate in the African savannah, palm trees in the South American savannah, and eucalyptus trees in the Australian savannah. A characteristic feature of the African savannah is a wide variety of herbivorous ungulates, which provide the existence of a variety of predators. In 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 chemical energy. Consumers are animals that eat plants or herbivores and thus indirectly depend on plants for energy. Decomposers are usually fungi and bacteria that decompose the dead remains of animals and plants into substances that can again be used by plants.

Niche - it is the role of the animal in the community, determined by its relationships both with other organisms and with the physical environment. So, herbivores usually eat plants, and herbivores, in turn, are eaten by predators. The species occupying this niche are different in different parts of the globe. For example, the niche of small herbivores in temperate zones in the Northern Hemisphere is occupied by rabbits and hares, in South America by agoutis and viscaches, in Africa by hyraxes and white-footed hamsters, and in Australia by wallabies.

Rice. 5.8. Distribution of major terrestrial biomes of the world.

In 1917, the American ecologist Grinnell first put forward the theory of niches, based on the study of the California mockingbird. (Toxostoma redivivum) - a bird that nests in dense foliage one to two meters above the ground. The location of the nest is one of the characteristics by which an animal's niche can be described. In mountainous areas, the vegetation necessary for nesting is found only in an ecological community called chaparral. The habitat of the mockingbird, described by the physical characteristics of the environment, is determined in part by the reaction of the mockingbird population to the situation in the niche. Thus, if the height of the nest above the ground is a decisive factor in escaping from predators, then there will be strong competition in the population for nest sites at the optimal height. If this factor were not so decisive, then more individuals would be able to build nests in other places. The habitat conditions in a given niche are also affected by competition from other species for nesting sites, food, etc. The habitat of the California mockingbird is determined in part by the niche situation, 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 the best places, and this affects the habitat of the species. Thus, the overall relationship of the mockingbird to habitat conditions, which is often referred to 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 (Fig. 5.9). Niche overlap leads to competition, especially when resources are scarce. Principle of competitive exclusion states that two species with identical 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. Niche overlap. The fitness of an animal can often be represented as a bell-shaped curve along some environmental gradient, such as temperature. Niche overlap (shaded area) occurs in the portion 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 the oaks of the mountainous coast in central California (Root, 1967). This group, called guild, are 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 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 must 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 plains tit (Parus inornatus) refers to a guild of leaf picking birds based on its foraging behavior; in addition, she is also a member of the guild of birds nesting in hollows due to nesting requirements.

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

Although in this case, five species of birds feed on insects, each species takes insects that differ in size and taxonomic position. The taxonomic categories of insects eaten by these five species overlap, but each species specializes in a particular taxon. Prey sizes overlap completely, but their means and variances are different, at least in some cases. Root (1967) also found that birds of these species are characterized by three types of foraging behavior:

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

2) picking up insects from the surface of leaves by a soaring bird;

3) catching flying insects.

The proportion of time that each species spends on one or another way 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 that guild develop all possible types of foraging behavior and use all kinds of prey.

Competition often results in the dominance of one species; this is reflected in the fact that dominant species have an advantage in the use of resources such as food, space and shelter (Miller, 1967; Morse, 1971). Based on the theory, one would expect that a species that becomes subordinate to another species would have to change its resource use in such a way as to reduce overlap with the dominant species. Usually in this case, the subordinate species reduces the use of some resources, thus reducing the width of the niche. In some cases, a subordinate species may 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 a dominant species, then its main niche is wider than that of the dominant species. Such cases have been noted in bees and New World blackbirds (Orians and Willson, 1964). Since priority in resource use belongs to dominant species, subordinate species can be excluded from niche space when resources are limited, their number is unpredictable, and foraging requires significant effort; and all this significantly reduces the fitness of the subordinate species in the area of ​​overlap. In such cases, subordinate species can be expected to be subject to significant selection pressure and change their fundamental niches, either through specialization or by developing resistance to a wider range of physical habitat conditions.

Adaptability of animal behavior

Naturalists and ethologists have discovered 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 only seems convincing because the various details and observations fit together too well; in other words, a good story can seem compelling simply because it is 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 be fitted together. The problem is that biologists, as scientists, have to evaluate data, and a good description is not always good data. As in a court of law, the data must be more than thorough and must carry some elements of independent verification.

One way to get data indicative of behavioral adaptability is to compare related species that occupy different habitats. A classic example of this approach is the work of Ester Cullen (1957) comparing the nesting habits of a rock-nesting kittiwake (Rissa tridactyla) and ground-nesting gulls such as the common (Lams ridibundus) and silver (Lams argentatus). Kittiwakes nest on rocky ledges inaccessible to predators and apparently evolved from ground-nesting gulls as a result of predation pressure. Kittiwakes have inherited some traits of ground-nesting gulls, such as the partially camouflaged coloration of their eggs. Eggs of ground-nesting birds are usually well camouflaged to protect against predators, but in kittiwakes, the color of the eggs cannot serve this function, as each nest is marked with conspicuous white droppings. Ground-nesting adults and juveniles are tidy and avoid defecation near the nest so as not to reveal its location. Thus, it seems most likely that the camouflage coloration 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 nest on very narrow rock ledges. She established that neither land animals such as rats nor birds such as herring gulls, which often prey on the eggs of birds nesting on the ground, prey on their eggs. Kittiwakes feed mainly on fish and do not devour eggs and chicks from neighboring nests, as gulls nesting on the ground often do. Kittiwakes appear to have lost most of the adaptations that protect other gulls from predators. For example, not only do they not mask the nest, they also rarely emit alarm calls and do not attack predators en masse.

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

Kittiwakes have many special adaptations for rock nesting. They have a light body and strong fingers and claws that allow them to cling to ledges that are too small for other gulls. Compared to ground-nesting gulls, adult kittiwakes have a number of behavioral adaptations to rocky habitats. Their behavior during fights is limited by strict stereotypes in comparison with relatives nesting on the ground (Fig. 5.12). They build rather elaborate cup-shaped nests using twigs and mud, while ground-nesting gulls build rudimentary nests from grass or seaweed without using mud 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 towards the rock. They snatch regurgitated food directly from the throats of their parents, while most gulls pick it up from the ground, where it is thrown by adults. Nestling gulls nesting on the ground run away and hide when frightened, while young kittiwakes remain in the nest. Chicks of gulls are characterized by cryptic coloration and behavior, while kittiwake chicks 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 occurs in one species but not in another, it may be due to differences in the way natural selection acts on the two species. For example, herring gulls remove eggshells near the nest in order to maintain nest camouflage because the inner white surface of the eggshell is highly visible. Evidence supporting this hypothesis comes from observations of kittiwakes that do not remove their shells. As we have already seen, kittiwake nests are not attacked by predators and their nests and eggs are not camouflaged. If eggshell removal serves primarily to maintain nest camouflage, then we are unlikely to find this in kittiwakes. However, if it serves other purposes, such as disease prevention, then this behavior would be expected to occur in kittiwakes. Kittiwakes usually keep the nest very clean and discard any foreign objects from it. Herring Gulls do not usually do this.

The above data will be further strengthened if we can show that other related species under the same selection pressure develop similar adaptations. One such example is given by Hailman (1965), who studied the Fork-tailed Gull nesting on rocks. (Lams furcatus) in the Galapagos Islands. Heilman studied various behaviors that are determined by the ability to prevent the danger of falling from 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 respective adaptations of fork-tailed gulls would be intermediate between those of kittiwakes and typical ground-nesting gulls. Fork-tailed gulls are subject to more predation than kittiwakes, and Heilman found some behaviors that appear to be driven by this difference. For example, as mentioned above, kittiwake chicks defecate on the edge of the nest, thus making it very conspicuous. Forked-tailed gull chicks defecate behind the edge of this edge. He found that fork-tailed gulls occupy an intermediate position between kittiwakes and other gulls in a number of characters, also associated with the intensity of predation. In this way, Heilman assessed those behavioral traits of forked-tailed gulls that are adaptations to the availability of available nesting space and the availability of nest sites and nesting material. He then decided to evaluate the data on which Cullen (1957) had based his hypothesis that the characteristic traits of kittiwakes are the result of selective pressures that accompany rock nesting. He selected 30 features 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 particular traits of kittiwakes are the result of an act of selection that accompanies rock nesting.

The work of Crook (Crook, 1964) on almost 90 species of weavers (Ploceinae) is another example of this comparative approach. These small birds are distributed throughout Asia and Africa. Despite their superficial similarity, the different types of weavers differ markedly in social organization. Some of them defend a large territory in which they build camouflaged nests, while others nest in colonies in which the nests are clearly visible. Crook found that the species living in the forests lead a solitary lifestyle, feed on insects, nests are masked in a large protected area. They are monogamous, sexual dimorphism is weakly expressed. Species living in the savannah are usually seed-eating, live in groups, nest colonially. They are polygamous, with males brightly colored and females dull.

Crook believed that since food was hard to come by in the forest, it was necessary for both parents to feed the chicks, and for that, the parents had to stay together during the breeding season. The density of insects that forest birds feed on is low, so a pair of birds must defend a large area to ensure adequate food supply for the chicks. Nests are well camouflaged and adult birds are dull-colored to prevent predators from revealing the location when they visit the nest.

In the savannah, seeds can be abundant in some places and few in others, an example of patchy food distribution. Foraging under such conditions is more efficient if the birds form groups to search a wide area. Nesting sites protected from predators are rare in the savanna, so many birds nest in the same tree. The nests are voluminous to provide protection from the heat of the sun, so the colonies are highly visible. For protection from predators, nests are usually built high up on thorny acacias or other similar trees (Figure 5.13). The female herself is able to feed the offspring, since there is a relatively large amount of food. The male almost does not participate in this and cares for other females. Males compete for nesting sites within the colony, and those who succeed may each attract several females while the 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 arranges a complex "performance" by hanging from the nest. If the male is successful in courtship, the female enters the nest. This attraction to the nest is typical of colonial weavers. The courtship ritual is quite different for bird species living in the forest, in which the male chooses a female, courts her at a noticeable distance from the nest, and then leads her to the nest.

Rice. 5.13. Weaver colony Ploceus cucullatus. Note that a large number of nests are relatively inaccessible to predators. (Photo by Nicholas Collias.)

The comparative approach has proved to be a fruitful method in studying the relationship between behavior and ecology. Birds (Lack, 1968), ungulates (Jarman, 1974), and primates (Crook and Gartlan, 1966; Glutton-Brock and Harvey, 1977) have been studied using this method. Some authors (Clutton-Brock, Harvey, 1977; Krebs, Davies, 1981) criticize the comparative approach, however, it provides satisfactory data regarding the evolutionary aspects of behavior, provided that appropriate measures are taken to avoid the substitution of concepts and overlapping evidence. Heilman (Hailman, 1965) considers the comparative method to be appropriate only in those cases where the comparison of two populations of animals allows conclusions to be drawn regarding 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 a comparative study can be tested independently without using the data obtained as a result of this study. It is not difficult to see that if there are interrelated differences in behavior and ecology between two populations, then this is not enough to say that these traits reflect the selection pressure that arises as a result of differences in the living conditions of these two populations. Differences arising from confounding variables or from comparing inappropriate taxonomic levels can be avoided by careful statistical analysis (Clutton-Brock and Harvey, 1979; Krebs and Davies, 1981).



Ministry of Education and Science of the Russian Federation

Federal State Budgetary Educational Institution

higher professional education

"Siberian State Industrial University"

Department of Ecology

discipline: Social ecology

on the topic: "Ecological niche"

Completed:

Student gr. ERM-12

Belichenko Ya.V.

Checked:

Assoc. Dugin

Novokuznetsk

Introduction………………………………………………………..……………….…. 3

1. Ecological niche…………………………….…………………………........... 4

1.1. The concept of ecological niche……………….…………………………. four

1.2. Width and overlap of niches…………………….……………………. 5

1.3. Niche Evolution……………………………………….……………….…10

2. Aspects of ecological niche…………………………….……………….….….12

3. The modern concept of ecological niche……………..………...................... 13

Conclusion………………………………………….……………………………… 16

List of used literature………………………………….………...... 19

Introduction

In this paper, the topic "Ecological niches" is considered. An ecological niche is a place occupied by a species (more precisely, its population) in a community, a complex of its biocenotic relationships and requirements for abiotic environmental factors. This term was introduced in 1927 by Charles Elton. The ecological niche is the sum of factors for the existence of a given species, the main of which is its place in the food chain.

An ecological niche is a place occupied by a species in a community. The interaction of a given species (population) with partners in the community to which it belongs as a member determines its place in the cycle of substances due to food and competitive links in the biocenosis. The term "Ecological niche" was proposed by the American scientist J. Grinnell (1917). The interpretation of an ecological niche as the position of a species for the purpose of feeding one or more biocenoses was given by the English ecologist C. Elton (1927). Such an interpretation of the concept of ecological niche makes it possible 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 single out the optimum zone and the limits of the deviations tolerated by the species - 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 by the entire course of evolutionary development. The place occupied by a species (its population) in space (spatial ecological niche) is more often called a habitat.

Let's take a closer look at ecological niches.

1. ecological niche

Any kind of organisms is adapted for certain conditions of existence and cannot arbitrarily change the habitat, diet, feeding time, breeding place, shelter, etc. The whole complex of relations to such factors determines the place that nature has allocated to a given organism, and the role that it must play in the general life process. All this is combined in the concept of an ecological niche.

1.1. The concept of an ecological niche

An ecological niche is understood as the place of an organism in nature and the whole way of its life activity, its life status, fixed in its organization and adaptations.

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 an ecological niche is interpreted mainly as a habitat, or a 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: the type of food, the time and place of feeding, who is the predator for this organism, etc. This is now called a 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 (the hyperspace niche).

That is, in the modern understanding of the 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 living organisms adjacent to it (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 rather narrow limits assigned to it from birth. However, its descendants can claim other ecological niches if they have undergone appropriate genetic changes.

ecological niche- a set of all environmental factors within which the existence of a species in nature is possible. concept ecological niche is 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 (i.e., the ecological niche was defined as a concept close to habitat).

Later, Ch. Elton (1927) defined an ecological niche as the position of a species in a community, emphasizing the particular importance of trophic relationships. Back in the late 19th and early 20th centuries, many researchers noticed that two species that are ecologically close and occupy a similar position in the community cannot coexist stably in the same territory. This empirical generalization was confirmed in the mathematical model of the 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, an 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 a species.

The divergence of ecological niches of different species through divergence occurs mainly due to confinement to different habitats, different food and different times of using the same habitat. Methods for estimating the width of the ecological niche and the degree of overlapping of ecological niches of various species 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 (abstract) of 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 values ​​of environmental factors under which the existence of a species (population) is theoretically possible is called fundamental ecological niche.

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

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. 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 idea of ​​an ecological niche:

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

2) trophic niche. It stands out especially because of the great importance of food as an environmental factor. The division of food niches in organisms of the same trophic level living together allows not only avoiding competition, but also contributes to a more complete use of food resources and, consequently, 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 bird species occupies a trophic niche strictly defined by its biological characteristics: some feed near the coast, others at a considerable distance, some fish at the surface, others at depth, etc.

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

3) multidimensional niche, or a niche as a hypervolume. The concept of a multidimensional ecological niche is associated with mathematical modeling. The whole set of combinations of values ​​of environmental factors 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 view complements the previous ones and is based on the functional similarity 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 "occupation" or even "position in society". It is in functional terms that they talk about environmental equivalents– species occupying 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, including 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 the gradients of external factors - temperature, humidity, pH, soil, etc. 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 the hypervolume niche. Therefore, the ecological niche of an organism depends not only on where it lives, but also includes the total amount of its environmental requirements.

Species that occupy the same niche in different geographical areas are called environmental 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 a section of their straight lines and planes corresponding to some selected environmental factors is widely used in ecology (Fig. 5.1). At the same time, depending on the nature of the factors that correspond to the considered particular function of well-being, one can distinguish between “climatic”, “trophic”, “edaphic”, “hydrochemical” and other niches, the so-called private niches.

A positive conclusion from the analysis of particular niches can be the conclusion from the contrary: if the projections of particular niches on 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 options for the mutual arrangement of niches of two types in the space of environmental factors: 1) separation (complete mismatch); 2) partial intersection (overlapping); 3) complete inclusion of one niche into another. ...

Separation of niches is a rather trivial case, reflecting the existence of species adapted to different ecological conditions. Of much greater interest are cases of partial intersection of niches. As mentioned above, the overlapping of projections even in 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 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 the 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.”

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