Biological interspecific competition is a natural process of struggle between different individuals for space and resources (food, water, light). It arises if species have similar needs. Another reason for the start of competition is the limited resources. If natural conditions give an excess of food, a struggle will not even arise between individuals with very similar needs. Interspecific competition can lead to the extinction of a 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 plant species. Deer consuming leaves of trees deprive bison of food. Typical rivals are mink and otter, driving each other out of contested water bodies.
The animal kingdom is not the only environment where interspecific competition is observed . Examples of such a struggle are found among plants. Conflict is not even the aboveground parts, but the root system. Some species inhibit others in many ways. Soil moisture, mineral substances are taken away. A striking 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 inhibits the development of neighbors. Interspecific competition between creeping wheatgrass and pine seedlings is similarly manifested.
Ecological niches
Competitive interaction can be very different: from peaceful coexistence to physical struggle. In mixed plantings, fast-growing trees inhibit slow-growing trees. Mushrooms inhibit bacterial growth through the synthesis of antibiotics. Interspecific competition can lead to the delimitation of ecological beggars and increase the number of differences between species. So, environmental conditions, the totality of relations with neighbors are changing. An ecological niche is not equivalent to habitat (the space where an individual lives). In this case, we are talking about the whole lifestyle. The habitat can be called an “address”, and the ecological niche can be called a “profession”.
Competition of Similar Species
In general, interspecific competition is an example of any interaction between species that negatively affects their survival and growth. As a result, the rivals either adapt to each other, or one opponent crowds out the other. This pattern is characteristic of any struggle, whether using the same resources, predation, or chemical interaction.
The pace of struggle increases if we are talking about similar or related to the same genus species. A similar example of interspecific competition is the history of gray and black rats. Previously, these different species of the same kind coexisted with each other in cities. However, due to its better fitness, gray rats replaced black ones, leaving them with forests as their habitat.
How can this be explained? Gray rats swim better, they are larger and more aggressive. These characteristics influenced the outcome to which the described interspecific competition led. Examples of such collisions are numerous. The struggle between blackbirds and songbirds in Scotland was very similar. And in Australia, bees brought from the Old World were replaced by smaller native bees.
Operation and interference
To understand in what cases interspecific competition occurs, it is enough to know that in nature there are no two species that would occupy the same ecological niche. If organisms are closely related and lead a similar lifestyle, they will not be able to live in the same place. When they nevertheless occupy a common territory, these species eat different foods or are active at different times of the day. One way or another, these individuals necessarily have a different trait, which gives them the opportunity to occupy different niches.
Outwardly peaceful coexistence can also be an example of interspecific competition. The relationships of some plant species are a similar example. Light-loving species of birch and pine protect spruce seedlings, dying in open places from freezing. This balance is broken sooner or later. Young spruce trees close and kill new seedlings of rocks that need the sun.
The neighborhood of different types of rock Nuthatch is another striking example of morphological and ecological separation of species, which leads to interspecific competition of biology. Where these birds live next to each other, their way of feeding and the length of the beak are different. In different habitats, this distinction is not observed. A separate issue of evolutionary doctrine is the similarities, differences in intraspecific, interspecific competition. Both cases of struggle can be divided into two types - exploitation and interference. What are they?
During operation, the interaction of individuals is indirect. They respond to a decrease in the amount of resources caused by the activity of competing neighbors. Diatoms consume food to such an extent that its availability decreases to a point where the rate of propagation and growth of the rival species 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 interspecific 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 are found in insects. In their class, asymmetric competition occurs twice as often as symmetric. Such an interaction in which one individual adversely affects another, and that other does not exert any influence on the opponent, is also called amenismism.
An example of such a struggle is known from observations of bryozoans. They compete with each other through fouling. These colonial species live on corals off the coast of Jamaica. Most of their competing individuals “defeat” opponents in the vast majority of cases. These statistics clearly demonstrate how asymmetric types of interspecific competition differ from symmetric ones (in which the chances of rivals are approximately equal).
Chain reaction
Among other things, interspecific competition may cause the restriction of one resource to entail the restriction of another resource. If a colony of bryozoans comes into contact with a rival colony, then there is a possibility of disruption of the course and food intake. This, in turn, leads to the cessation of growth and occupation of new areas.
A similar situation arises in the case of the “root war”. When an aggressive plant obscures an opponent, the oppressed body feels a lack of incoming solar energy. Such starvation causes a slowdown in root growth, as well as a deterioration in the use of minerals and other resources in soil and water. Competition of plants can affect both shoots from roots and vice versa from shoots to roots.
Algae example
If a species has no competitors, then its niche is considered not ecological, but fundamental. It is determined by a combination of resources and conditions under which the body can maintain its population. When competitors appear, the view from the fundamental niche falls into the realized niche. Its properties are determined by biological rivals. This pattern proves that any interspecific competition is the cause of reduced viability and fertility. In the worst case, neighbors crowd out the body into that part of the ecological niche where it can not only inhabit, but also acquire offspring. In this case, the species faces the threat of its complete extinction.
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 the biological struggle for survival. If two competing species Asterionella and Synedra are placed in the same tube, the latter will receive a habitable niche, and Asterionella will die.
Other results are given by the coexistence of Aurelia and Bursaria. Being neighbors, these species will receive their own niches realized. In other words, they will share resources without fatal harm to each other. Aurelia will concentrate at the top and will consume suspended bacteria. Bursaria will settle on the bottom and feed on yeast cells.
Resource sharing
An example of Bursaria and Aurelia shows that peaceful existence is possible with differentiation of niches and sharing of resources. Another example of this pattern is the struggle of Galium algae species. Their fundamental niches include alkaline and acidic soils. With the emergence of the struggle between Galium hercynicum and Galium pumitum, the first species is limited to acidic soils, and the second to alkaline soils. Such a phenomenon in science is called mutual competitive exclusion. At the same time, algae need both alkaline and acidic environments. Therefore, both species cannot coexist in one niche.
The principle of competitive exclusion is also called the Gause principle by the name of the Soviet scientist Georgy Gause, who discovered this pattern. It follows from this rule that if two species cannot separate their niches due to some circumstances, then one will surely exterminate or supplant the other.
For example, the sea acorns Chthamalus and Balanus coexist in the neighborhood only for the reason that one of them, due to sensitivity to drying, lives exclusively in the lower part of the coast, and the other is able to live in the upper part, where it does not face rivalry. Balanus pushed Chthamalus, but could not continue its expansion on land due to their physical disabilities. The crowding out occurs under the condition that a strong competitor has a realized niche that completely covers the fundamental niche of a weak adversary involved in a dispute over habitat.
Gause principle
Explanations of the causes and consequences of biological control are engaged in ecologists. When it comes to a specific example, sometimes it’s quite difficult for them to determine what the principle of competitive exclusion is. So difficult for science is the rivalry of different types of salamanders. If it is impossible to prove that niches are divided (or to prove the opposite), then the principle of competitive exclusion remains an assumption.
At the same time, the truth of Gauze's regularities has long been confirmed by many recorded facts. The problem is that even if the separation of niches does occur, then its cause is not necessarily an interspecific struggle. One of the urgent tasks of modern biology and ecology is to determine the causes of the disappearance of some individuals and the expansion of others. Many examples of such conflicts are still poorly studied, which gives a lot of space for future specialists to work.
Fixture and Extrusion
The life of each organism is highly dependent on a host-parasite and a predator-prey relationship. 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 the remaining species. They are connected by one ecosystem, which means that in order to continue their existence (and the existence of offspring), organisms must evolve, adapting to new living conditions. Most of the living creatures disappeared, not for some reason, but only in connection with the pressure of predators and competitors.
Evolution race
The struggle for existence continues on 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 are the forms of competition themselves.
The rules of struggle are constantly changing. In this they differ from abiotic factors. For example, the climate on the planet also changes without stopping, but it changes randomly. Such innovations do not necessarily harm organisms. But competitors always evolve to the detriment of neighbors.
Predators improve hunting methods, prey improve the mechanisms of this protection. If any of them ceases to evolve, this species will be doomed to crowding out and extinction. This process is a vicious circle, as some changes give rise to others. The eternal engine of nature pushes life to constantly move forward. Interspecific struggle in this process plays the role of the most effective tool.