INTRASPECIFIC COMPETITION: CHARACTERISTICS, TYPES AND EXAMPLES - BIOLOGY - 2024

The intraspecific competition is a type of interaction where members of the same species pursue a common limited resource. It must be clarified that competition is a type of ecological interaction that not only applies to animals, it also applies to other living beings - such as plants. Competition occurs for a wide variety of resources, such as available space, food, places of refuge, territory, couples, among others.

Intraspecific competition is opposed to the concept of interspecific competition, where competition for resources occurs between members of different species. As the ecological needs of individuals of the same species are clearly more similar than between different species, intraspecific competition is usually stronger.

Males competing. Source: Brocken Inaglory

These two types of biotic interactions are not mutually exclusive. In other words, the same species experiences inter and intraspecific competition, generating the complex patterns of interaction that we observe in nature.

Overview of intraspecific competition

In ecosystems, individuals do not remain isolated. They are in constant interaction with other organisms. It is common for members of a species to have contact with their peers and compete.

Competition is density dependent

In ecology, there is a concept called carrying capacity, which quantifies the maximum size of the population that the environment where they live can support, taking into account the amount of resources that exist.

Thus, when the carrying capacity is saturated, the competition between individuals begins to be stronger. This phenomenon can cause drastic drops in population size.

Therefore, this type of competition is “density dependent”. At low densities, competition does not have a marked effect on the survival of members; contrary to what happens when the population increases its size.

As population density increases, resources become less available, thus increasing competition among members of the species.

Reduced reproductive success

One of the characteristics of competition is the reduction of the reproductive success of the members who participate in said interaction. Although one of the competitors will obtain more resources than his “weaker” or disadvantaged partner, the long-term interaction has negative consequences for both parties.

Types

Two basic types of intraspecific competition have been identified:

Intraspecific competition for interference

In this type of competition, a hierarchy is established within the individuals of the population, through aggressive and oppressive behaviors.

Through direct interactions, dominant members limit access to resources to other members. The same type of competition occurs with territorial animals.

Reproductive success is greater in individuals who took an aggressive attitude and managed to dominate the group. In the case of mating, competition for interference may apply when one or a few males restrict access to females.

Intraspecific competition by exploitation

In the first type of competition, the fight is direct restricting access to the variety of resources. In contrast, competition for exploitation involves the use of the resource or resources that are limited, exhausting their availability for other members of the population.

In this case, the interactions are of the indirect type - since the competition is established by the elimination of the resource (in this case, the food) and not by direct contact with the individual.

Factors that affect intraspecific competition

Influence of the age of the competitors

If we think of all possible scenarios of competition between members of the same species, we must ask ourselves whether the competition occurs between members of a particular cohort or whether it extends to members of different age groups - that is, between members of different ages.

In some species, observations from the natural world suggest that adult and juvenile members of the same species have little chance of competing, as they generally use different resources.

For example, in the case of anemones the use of resources is clearly delimited. The adult specimens have tentacles considerably larger than the juveniles.

The method of predation of these animals consists of waiting for the appearance of the prey and then capturing it, so that adult individuals have a separate prey range from the prey that the younger ones catch with their small tentacles.

This trend has been reported in other groups of organisms. In fish, adult individuals are located in specific habitats, with a spatial separation of resources between age classes.

Competitors' spatial arrangement

The pattern of disposition in the physical environment of members of the population affects competition. This fact is illustrated in predators, where organisms have exclusive territories in which each individual hunts and feeds.

Although certain individuals are unable to obtain a region for themselves, those who do manage to ensure the availability of prey until reproduction. In this case the competition is not directly for the food, but for the territory.

Evolutionary perspective

In the light of Darwinian evolutionary theory, intraspecific competition plays a leading role in the mechanism.

When we think of natural selection, it is almost impossible not to conjure up the famous - and misguided - phrase "survival of the fittest." We can instantly relate it to the melee confrontations of a carnivore chasing its prey.

However, the correct thinking is to relate natural selection to intraspecific competition, and not necessarily fighting, between members of the same species (this does not mean that interactions with different species have no evolutionary consequences).

The individuals that “outperform” their opponents - in terms of reproduction, are those that increase their frequency in the population.

Examples

Competition between moths of the genus

In the northeastern United States, the persistence of a moth considered a pest of the genus Lymantría is very common.

It is an example of extreme intraspecific competition, as the population increases in size rapidly and this disproportionate increase depletes resources.

The life cycle of the insect is not in accordance with the availability of resources, therefore when the caterpillars manage to complete the metamorphosis, there is no longer food available and the population declines with the same vigor with which their number increased.

References

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