Interspecific competition in biology

Biological interspecific competition is a natural process of struggle between different individuals for space and resources (food, water, light). It occurs when species have similar needs. Another reason for the beginning of competition is limited resources. If natural conditions produce an excess of food, the struggle will not even arise between individuals with very similar needs. Interspecific competition can lead to the extinction of the species or its displacement from the previous habitat.

Struggle for existence

In the XIX century interspecific competition was studied by researchers involved in the formation of the theory of evolution. Charles Darwin noted that the canonical example of such a struggle is the coexistence of herbivorous mammals and locusts, feeding on the same species of plants. Eating leaves of trees deer deprive feed of bison. Typical rivals are the mink and otter, driving each other out of the challenged reservoirs.

The animal kingdom is not the only environment where interspecific competition is observed. Examples of such a struggle are found among plants. Conflicted not even the above-ground parts, but the root systems. Some species oppress others in many ways. It takes away the soil moisture, minerals. A vivid example of such actions is the activity of weeds. Some root systems with the help of their secretions change the chemical composition of the soil, which inhibit the development of neighbors. Similarly, interspecies competition is observed between the creeping moose grass and the seedlings of the pine.

Ecological niches

Competitive interaction can be very different: from peaceful coexistence to physical struggle. In mixed plantings, fast-growing trees depress slow growing. Fungi suppress the growth of bacteria by the synthesis of antibiotics. Interspecific competition can lead to the delimitation of ecological poverty and the increase in the number of differences between species. So, the environmental conditions change, the set of relations with neighbors. An ecological niche is not equivalent to a habitat (the space where an individual lives). In this case we are talking about the whole way of life. A habitat can be called an "address", and an ecological niche is a "profession".

Competition of similar types

In general, interspecific competition is an example of any interaction between species, negatively affecting their survival and growth. As a result, rivals either adjust to each other, or one opponent dislodges the other. This pattern is typical for any struggle, whether it is the use of the same resources, predation or chemical interaction.

The rate of struggle increases, if it is a question of similar or belonging to the same genus species. A similar example of interspecific competition is the history of gray and black rats. Previously, these different kinds of the same kind were neighbors to each other in the cities. However, due to their better fitness, gray rats drove out the blacks, leaving them as a forest habitat.

How can this be explained? Gray rats swim better, they are larger and more aggressive. These characteristics and influenced the result, which led to the described interspecific competition. Examples of such collisions are numerous. Very similar was the struggle between thrushes-derbyas and songbirds in Scotland. And in Australia, the bees brought from the Old World drove out smaller bees of the size of native bees.

Operation and interference

To understand when an interspecific competition occurs, it is enough to know that in nature there are no two species that occupy the same ecological niche. If the organisms are closely related and lead a similar way of life, they can not live in the same place. When they still occupy a common territory, these species eat different foods or are active at different times of the day. Either way, these individuals necessarily have a different attribute, which enables them to occupy different niches.

Externally, peaceful coexistence can also be an example of interspecific competition. The relationship of some plant species is a similar example. Photophilous rocks of birch and pine protect shoots of spruce, dying in open places from freezing. This balance is sooner or later violated. Young firs close and kill new shoots of rocks that need sun.

The proximity of different species of rocky nuthathes is another vivid example of the morphological and ecological separation of species, to which the interspecific competition of biology leads. Where these birds live next to each other, their way of harvesting food and the length of the beak are different. In different areas of habitat this distinction is not observed. A separate issue of evolutionary doctrine is similarity, differences of intraspecific, interspecific competition. Both cases of struggle can be divided into two types - operation and interference. What are they?

In operation, the interaction of individuals is indirect. They react to a decrease in the amount of resources caused by the activity of their neighbors-competitors. Diatom algae consume food to such an extent that its availability is reduced to a level where the rate of reproduction and growth of a species-rival becomes extremely low. Other types of interspecific competition are interference. They are shown by sea acorns. These organisms do not allow neighbors to be fixed on stones.

Amensalism

Other similarities between intraspecific and interspecies competition are that both of them can be asymmetric. In other words, the consequences of the struggle for existence for the two species will not be the same. Especially often, such cases occur in insects. In their class, asymmetric competition arises twice as often as the symmetric one. This interaction, in which one individual adversely affects the other, and the other does not have any influence on the opponent, is also called amensalism.

An example of such a struggle is known from observations of bryozoans. They compete with each other by fouling. These colonial species live on corals alongside the coast of Jamaica. Most of their competing individuals "defeat" opponents in the vast majority of cases. These statistics clearly demonstrate how asymmetrical types of interspecies competition differ from symmetric (in which the chances of rivals are approximately equal).

Chain reaction

In addition, interspecific competition can cause the restriction of one resource to entail the restriction of another resource. If the colony of bryozoans comes into contact with the colony-rival, then there is a probability of disturbance of the flow and intake of food. This, in turn, leads to the cessation of sprawl and occupation of new areas.

A similar situation arises in the case of a "war of roots". When an aggressive plant obscures an opponent, the depressed organism feels a lack of incoming solar energy. This starvation causes a slowdown in root growth, as well as a deterioration in the use of minerals and other resources in soil and water. The competition of plants can influence both from the roots to the shoots, and vice versa from the shoots to the roots.

Example of algae

If the species does not have competitors, then its niche is not considered ecological, but fundamental. It is determined by the totality of resources and conditions under which the organism can support its population. When competitors appear, the view from the fundamental niche falls into the realized niche. Its properties are determined by biological opponents. This pattern proves that any interspecific competition is the reason for the decrease in viability and fertility. In the worst case, neighbors displace the body in that part of the ecological niche where it can not only live, but also acquire offspring. In this case, the species faces the threat of its complete disappearance.

Under experimental conditions, the fundamental niches of diatoms are provided by the cultivation regime. It is on their example that it is convenient for scientists to investigate the phenomenon of biological struggle for survival. If two competing species of Asterionella and Synedra are placed in a single tube, the latter will receive a niche that is fit for life, and Asterionella will die.

Other results are provided by the coexistence of Aurelia and Bursaria. Being neighbors, these species will get their own realized niches. In other words, they will share resources without fatal harm to each other. Aurelia will concentrate at the top and consume the weighed bacteria. Bursaria will settle on the bottom and feed on yeast cells.

Resource Sharing

The example of Bursaria and Aurelia shows that peaceful existence is possible when differentiating niches and dividing resources. Another example of this pattern is the struggle of algae species Galium. Their fundamental niches include alkaline and acidic soils. With the onset of the struggle between Galium hercynicum and Galium pumitum, the first species will confine itself to acidic soils, and the second will be limited to alkaline soils. This phenomenon in science is called a mutual competitive exception. Algae need both an alkaline and an acidic environment. Therefore, both species can not coexist in the same niche.

The principle of competitive exclusion is also called the Gause principle, named after the Soviet scientist Georgy Gause, who discovered this pattern. From this rule it follows that if two species can not share their niches because of some circumstances, then one will necessarily exterminate or displace the other.

For example, the marine acorns Chthamalus and Balanus coexist in the neighborhood only because one of them, due to the sensitivity to drying, lives exclusively in the lower part of the coast, and the other is able to dwell in the upper part where it does not face rivalry. Balanus pushed out Chthamalus, but could not continue their expansion on land due to their physical disabilities. Repression occurs under the condition that a strong competitor has an implemented niche completely overlapping the fundamental niche of a weak opponent, drawn into a dispute over the habitat.

The Gause principle

Environmentalists are engaged in explaining the causes and consequences of biological warfare. When it comes to a specific example, it is sometimes difficult for them to determine what the principle of competitive exclusion is. Such a difficult question for science is the rivalry of different types of salamanders. If it is impossible to prove that the niches are divided (or to prove the opposite), then the operation of the principle of competitive exclusion remains only an assumption.

In this case, the truth of the regularity of Gause has long been confirmed by a set of fixed facts. The problem is that even if the niche division occurs, its cause is not necessarily the interspecific struggle. One of the urgent tasks of modern biology and ecology is to determine the causes of the extinction of some individuals and the expansion of others. Many examples of such conflicts are still poorly understood, which gives a large space for future specialists.

Adaptation and displacement

The life of each organism depends heavily on a host-parasite relationship and predator prey. It is formed not only by abiotic conditions, but also by the influence of other plants, animals and microorganisms. It is impossible to get rid of or hide from these connections, since absolutely everything in nature is interconnected.

Improvement of one species will necessarily lead to a deterioration in the life of other species. They are linked by one ecosystem, and this means that to continue their existence (and the existence of offspring), organisms must evolve, adapting to new habitat conditions. Most of the living things disappeared not for some reason, but only because of the pressure of predators and competitors.

Evolutionary race

The struggle for existence continues on the Earth exactly since the first organisms appeared on it. The longer this process lasts, the more species diversity appears on the planet and the more diverse forms of competition become.

The rules of the fight are constantly changing. In this they differ from abiotic factors. For example, the climate on the planet is also changing without stopping, but it varies chaotically. Such innovations do not necessarily harm organisms. But competitors always evolve to the detriment of their neighbors.

Predators improve hunting methods, victims improve the mechanisms of this protection. If one of them ceases to evolve, this species will be doomed to repression and disappearance. This process is a vicious circle, because some changes generate others. The eternal engine of nature pushes life to a constant movement forward. Interspecific struggle in this process plays the role of the most effective tool.