Intraspecific vain occurs when two or much more individuals the the same species simultaneously demand use of a restricted resource (Wilson, 1975).

You are watching: How does competition affect population growth

From: good White Sharks, 1996

Related terms:

M.J. Vanni, ... M.J. Horgan, in Encyclopedia the Inland Waters, 2009

Intraspecific Competition

Intraspecific compete is a common and important communication for many aquatic species. A standard laboratory examine by L. B. Slobodkin showed decreased growth, survival, and reproduction of Daphnia when population size was high, as a an outcome of exploitative competition, and also served together the communication of subsequent researches on competition in zooplankton. One result of intraspecific competition is logistic population growth (called sigmoidal or S-shaped growth); population growth is virtually exponential when numbers room low, yet then expansion rate is diminished progressively as the population expands, and eventually the population approaches its moving capacity. Logistic development of aquatic populations has been demonstrated continuously in laboratory research studies of aquatic algae, bacteria, protozoans, and metazoans. It has been prove less often in the field, probably due to the fact that it is an overwhelming to observe colonization events that normally precede logistic growth.

Interference vain can also be critical mechanism that intraspecific competition. Many zooplankton taxa do autotoxins, which are chemicals that inhibit feeding or increase mortality in conspecifics. Because that example, people of the rotifer Synchaeta pectinata produce an autotoxin the reduces expansion rate and also increases mortality that other individuals of the exact same species. Autotoxin results have additionally been prove in a naval phytoplankton species. It is likely that autotoxic effects are common among freshwater organisms, but tiny research has actually been directed towards this phenomenon.

One consequence of intraspecific competition is stunted development of fish in dense populations. Fisheries managers observed long earlier that fish in a crowded populace (or through low food availability) often show low (stunted) expansion rates and thus are lot smaller 보다 individuals growing in a populace with couple of individuals (or with abundant resources). Stunted development has plenty of implications. Tiny and huge fish regularly rely on different food resources, therefore a stunted populace may have food net effects different from those of a population with bigger individuals. In addition, smaller people may be more vulnerable come predators, especially other fish that space gape-limited. Stunted populations additionally may it is in less preferable for recreational and commercial harvest.

Intraspecific compete can also lead to boosted variability in human body size. Compete is often highly asymmetric, definition that that affects some people much much more than others. This can be because some people are inherently better competitors, or since some people arrive at a site (or space born) previously than others and thus preempt resources. Premium or early-arriving people may with a relatively large size when inferior rivals or so late arrivers suffer reduced body size. Regularly there is a gradient in competitive capability or come times, and also a populace growing under intraspecific competition display screens a broad distribution that sizes among individuals of equal age. Together asymmetries have been prove in fish, amphibians, and insects. Distinctions in dimension initiated through intraspecific competition have the right to become intensified over time through size-dependent vain superiority. One individual the gains one initial advantage (e.g., by arriving early or by having a slightly bigger initial size) will certainly grow more rapidly than the mean individual. This individual may use a broader range of resources (e.g., bigger fish can consume a wider range of food items), bring about a additional gain in size family member to various other individuals. This distinction in size may become an ext pronounced over time.

Size distinctions can also set up hierarchies in which huge individuals room superior via interference competition because larger individuals may be far better at guarding territories, gaining accessibility to mates, or enduring aggressive interactions v conspecifics.

O. Gilad, in Encyclopedia that Ecology, 2008


Competition is defined as an interaction between two or more individuals that the same populace or two or an ext populations in which every negatively influence the various other in accessibility to a minimal resource(s) (food, water, nesting sites, shelter, mates, etc.). Mutualism is characterized as one interaction in between populations the is favorable to both. Two main varieties of competition are identified: intraspecific competition and interspecific competition.

Intraspecific Competition

Intraspecific vain is a competition in between individuals indigenous the same varieties (cospecifics). The result of vain on each individual in ~ the species depends ~ above the type of competition the takes place. ‘Contest-competition’ may be passive or energetic and may result in different outcomes. A types that competes because that a limited resource whereby all people consume equal quantities until the resource is depleted, may result in all people of that population dying of starvation. ~ above the other hand, and also the an ext common outcome is, when one separation, personal, instance competes and also wins end the resource, and also by exploiting that resource it continues to survive. Two an easy types have actually been figured out for intraspecific competition:


Interference (adapted) intraspecific competition. This occurs in varieties that create hierarchies through aggressive habits where one or an ext individuals in ~ the population hold a leading status end the others. Through direct interaction these people will border or prevent accessibility of much more subordinate people to a resource. This kind of compete may likewise occur when people within a varieties establish territories and limit the access of rather to a resource. In this kind of competition just those individuals who are dominant or host territories will rise their reproduction success. It is sometimes dubbed ‘contest competition’ denote displays and also contents between individuals for accessibility to a source (usually mates).


Exploitation (contest) intraspecific competition. This occurs between individuals the the same population exploiting the exact same resources and also reducing or depleting its ease of access to others. This compete is indirect interactions between individuals such together deleting of a food source.

Intraspecific compete is influenced not just by the kind of vain but likewise by the kind of resource. A territory, i m sorry is no depletable, will affect the survivorship the future generations. Competition over consumables, such as food, may an outcome in decreased availability for future generations and also such resources may need time to recover.

See more: Convert & Download Nelly Here Comes The Boom Download, Convert & Download Nelly

Intraspecific competition is density dependent and may reason density-dependent mortality. At short densities no intraspecific competition exists and also competition for resources does no play a duty in survivorship. As densities increase, a threshold is got to where density starts to influence mortality through source availability. Once plotted together a graph in state of populace growth rate, the result is one of two people a J-shaped growth or one S-shaped/sigmoidal curve, both described as logistic growth.

Logistic growth models

where N is the size of the populace with a limit implemented on that by restricted resources, t is time, and r is growth rate. Figure 1 mirrors that in this script (J-shaped growth) populace size enhanced rapidly or exponentially and also due come an outside environmental factor (limited sources for example) the population halts its expansion abruptly. Population size (density) might remain in ~ its maximum for a specific period of time, or may decrease quickly. In the S-shaped expansion model the population grows gradually at first, increases with time, and as environmental components (such as limited resources) start to take it affect, populace growth slow down till equilibrium is reached: