Scramble competition

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Grass can be a limited resource for grazing cows Cows at dawn.jpg
Grass can be a limited resource for grazing cows

In ecology, scramble competition (or complete symmetric competition or exploitation competition) refers to a situation in which a resource is accessible to all competitors (that is, it is not monopolizable by an individual or group). However, since the particular resource is usually finite, scramble competition may lead to decreased survival rates for all competitors if the resource is used to its carrying capacity. Scramble competition is also defined as "[a] finite resource [that] is shared equally amongst the competitors so that the quantity of food per individual declines with increasing population density". [1] A further description of scramble competition is "competition for a resource that is inadequate for the needs of all, but which is partitioned equally among contestants, so that no competitor obtains the amount it needs and all would die in extreme cases."

Contents

Types of intraspecific competition

Researchers recognize two main forms of intraspecific competition, where members of a species are all using a shared resource in short supply. [2] These are contest competition and scramble competition. [1]

Contest competition

Contest competition is a form of competition where there is a winner and a loser and where resources can be attained completely or not at all. Contest competition sets up a situation where "each successful competitor obtains all resources it requires for survival or reproduction". [1] Here "contest" refers to the fact that physical action plays an active role in securing the resource. Contest competition involves resources that are stable, i.e. food or mates. Contests can be for a ritual objective such as territory or status, and losers may return to the competition another day to try again. [3]

Scramble competition

In scramble competition resources are limited, which may lead to group member starvation. [3] Contest competition is often the result of aggressive social domains, including hierarchies or social chains. [4] Conversely, scramble competition is what occurs by accident when competitors naturally want the same resources. [4] These two forms of competition can be interwoven into one another. Some researchers have noted parallels between intraspecific behaviors of competition and cooperation. [4] These two processes can be evolutionarily adopted and they can also be accidental, which makes sense given the aggressive competition and collaborative cooperation aspects of social behavior in humans and animals. [4] To date, few studies have looked at the interplay between contest and scramble competition, despite the fact that they do not occur in isolation. There appears to be little understanding of the interface between contest competition and scramble competition in insects. [5] Much research still needs to be conducted concerning the overlap of contest and scramble competition systems. [5] Contests can arise within a scramble competition system and conversely, scramble competition "may play a role in a system characterized by interference". [5]

Population effects

Population can be greatly affected by scramble competition (and contest competition). Intraspecific competition normally leads to a decline of organisms. [4] For example, the more time that an individual spends seeking food and reproduction opportunities, the less energy that organism naturally has to defend oneself against predators, resulting in a "zero-sum game". [2] Competition is a density dependent effect, and scramble competition is no exception. Scramble competition usually involves interactions among individuals of the same species, which makes competition balanced and often leads to a decline of population growth rate as the amount of resources depletes. [6]

The Ricker Model, [1] is used to model scramble competition. It was originally formulated to study the growth of salmon populations and is given by the equation Pn+1 = R(Pn) = Pner(1-Pn/k), where Pn is the population at the nth time period, r is the Malthusian growth rate, and k is the carrying capacity of the population. The Ricker model, and a few other well-known population models, can be explicitly derived from individual-level processes assuming scramble competition and a random distribution of individuals among resources. [7]

Some researchers have noted that in certain species, such as the horseshoe crab, males are most successful at mating when they are able to practice scramble competition polygyny where they do not defend their territory but rather mate and move on, thus providing the highest likelihood of species survival and reproductive prowess. [8]

Examples

There are many examples of scramble competition within the environment. For example, cows grazing in a grassland could be operating under a scramble competition. This illustration of cows eating grass is scramble competition because there are limited resources, there is only so much grass to be eaten before all the food resource is depleted. Additionally, there is no way that others can limit the amount of resources or the access to resources that the other cows receive. [9]

Another example of scramble competition is forest defoliators. If their larvae can find shelter and food then survival is possible, but when all the foliage is destroyed then the population decreases. Their synchronized life cycle increases competition for specific resources; this greatly affects their ability to receive resources including food and shelter due to the overwhelming population increase at certain times of the year. [6]

The red spotted newt exhibits sexual dimorphism Red-spotted newt (N. v. viridescens).jpg
The red spotted newt exhibits sexual dimorphism

Scramble competition can also be seen with the example of red spotted newts. Charles Darwin (1871) first explored the concept of "sexual dimorphism" which states that, "most sexually dimorphic species are also the most polygynous" which would enable males to "outcompete other males through female choice, combat, or scrambles to encounter females would be favored by selection, and sexual dimorphism would result". [10] The key to red-spotted newts increased success in scramble competition is the newts enhanced or strengthened tailfins. [10]

Another example of scramble competition is the success of small beetles over large beetles. [11] While larger beetles, similar to larger animals in general, tend to win more often in contest competition, the opposite can be true in a scramble competition. [11] Specifically with beetles, scramble competition is dependent on male movement and locomotion so that the beetle that can move faster is more likely to be successful in attaining resources, mates and food. Smaller beetles fare better in scramble competition for shelter, which could one day lead to the evolutionary adaptation of smaller beetle structures for survival purposes. The flux of contest and scramble competition in this example is important to note because it truly depends on the context of each individual to determine which type of competition is most suitable.

Scramble competition also exists in lepidopterans. For example, male mourning cloak butterflies will fly around in search for widely dispersed females. [12]

Another example of scramble competition exists in Lactrodectus hesperus, the western black widow spider. There is a male-bias or skew within the sexually active population of this species, which means that females are a finite "resource". So, while no male has a monopoly over the females, the males who reach the female first will come out on top in the world of sexual reproduction. [13]

See also

Related Research Articles

Ecological selection refers to natural selection without sexual selection, i.e. strictly ecological processes that operate on a species' inherited traits without reference to mating or secondary sex characteristics. The variant names describe varying circumstances where sexual selection is wholly suppressed as a mating factor.

<span class="mw-page-title-main">Amplexus</span> Type of mating behavior exhibited by some externally fertilizing species

Amplexus is a type of mating behavior exhibited by some externally fertilizing species in which a male grasps a female with his front legs as part of the mating process, and at the same time or with some time delay, he fertilizes the eggs, as they are released from the female's body. In amphibians, females may be grasped by the head, waist, or armpits, and the type of amplexus is characteristic of some taxonomic groups.

<span class="mw-page-title-main">Behavioral ecology</span> Study of the evolutionary basis for animal behavior due to ecological pressures

Behavioral ecology, also spelled behavioural ecology, is the study of the evolutionary basis for animal behavior due to ecological pressures. Behavioral ecology emerged from ethology after Niko Tinbergen outlined four questions to address when studying animal behaviors: What are the proximate causes, ontogeny, survival value, and phylogeny of a behavior?

<i>Ursus</i> (mammal) Genus of bears

Ursus is a genus in the family Ursidae (bears) that includes the widely distributed brown bear, the polar bear, the American black bear, and the Asian black bear. The name is derived from the Latin ursus, meaning bear.

Evolutionary game theory (EGT) is the application of game theory to evolving populations in biology. It defines a framework of contests, strategies, and analytics into which Darwinian competition can be modelled. It originated in 1973 with John Maynard Smith and George R. Price's formalisation of contests, analysed as strategies, and the mathematical criteria that can be used to predict the results of competing strategies.

The marginal value theorem (MVT) is an optimality model that usually describes the behavior of an optimally foraging individual in a system where resources are located in discrete patches separated by areas with no resources. Due to the resource-free space, animals must spend time traveling between patches. The MVT can also be applied to other situations in which organisms face diminishing returns.

<span class="mw-page-title-main">Anisogamy</span> Sexual reproduction involving a large, female gamete and a small, male gamete

Anisogamy is a form of sexual reproduction that involves the union or fusion of two gametes that differ in size and/or form. The smaller gamete is male, a sperm cell, whereas the larger gamete is female, typically an egg cell. Anisogamy is predominant among multicellular organisms. In both plants and animals gamete size difference is the fundamental difference between females and males.

<span class="mw-page-title-main">Intraspecific competition</span>

Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to reproduce. By contrast, interspecific competition occurs when members of different species compete for a shared resource. Members of the same species have rather similar requirements for resources, whereas different species have a smaller contested resource overlap, resulting in intraspecific competition generally being a stronger force than interspecific competition.

<span class="mw-page-title-main">Competition (biology)</span> Interaction where the fitness of one organism is lowered by the presence of another organism

Competition is an interaction between organisms or species in which both require a resource that is in limited supply. Competition lowers the fitness of both organisms involved since the presence of one of the organisms always reduces the amount of the resource available to the other.

Monogamous pairing in animals refers to the natural history of mating systems in which species pair bond to raise offspring. This is associated, usually implicitly, with sexual monogamy.

In ecology, an ideal free distribution (IFD) is a theoretical way in which a population's individuals distribute themselves among several patches of resources within their environment, in order to minimize resource competition and maximize fitness. The theory states that the number of individual animals that will aggregate in various patches is proportional to the amount of resources available in each. For example, if patch A contains twice as many resources as patch B, there will be twice as many individuals foraging in patch A as in patch B.

<span class="mw-page-title-main">Cannibalism</span> Consuming another individual of the same species as food

Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, both in ancient and in recent times.

<span class="mw-page-title-main">Interspecific competition</span> Form of competition

Interspecific competition, in ecology, is a form of competition in which individuals of different species compete for the same resources in an ecosystem. This can be contrasted with mutualism, a type of symbiosis. Competition between members of the same species is called intraspecific competition.

<span class="mw-page-title-main">Red flour beetle</span> Species of beetle

The red flour beetle is a species of beetle in the family Tenebrionidae, the darkling beetles. It is a worldwide pest of stored products, particularly food grains, and a model organism for ethological and food safety research.

A biological ornament is a characteristic of an animal that appears to serve a decorative function rather than a utilitarian function. Many are secondary sexual characteristics, and others appear on young birds during the period when they are dependent on being fed by their parents. Ornaments are used in displays to attract mates, which may lead to the evolutionary process known as sexual selection. An animal may shake, lengthen, or spread out its ornament in order to get the attention of the opposite sex, which will in turn choose the most attractive one with which to mate. Ornaments are most often observed in males, and choosing an extravagantly ornamented male benefits females as the genes that produce the ornament will be passed on to her offspring, increasing their own reproductive fitness. As Ronald Fisher noted, the male offspring will inherit the ornament while the female offspring will inherit the preference for said ornament, which can lead to a positive feedback loop known as a Fisherian runaway. These structures serve as cues to animal sexual behaviour, that is, they are sensory signals that affect mating responses. Therefore, ornamental traits are often selected by mate choice.

Polygyny is a mating system in which one male lives and mates with multiple females but each female only mates with a single male. Systems where several females mate with several males are defined either as promiscuity or polygynandry. Lek mating is frequently regarded as a form of polygyny, because one male mates with many females, but lek-based mating systems differ in that the male has no attachment to the females with whom he mates, and that mating females lack attachment to one another.

<span class="mw-page-title-main">Sexual selection in insects</span>

Sexual selection in insects is about how sexual selection functions in insects. The males of some species have evolved exaggerated adornments and mechanisms for self-defense. These traits play a role in increasing male reproductive expectations by triggering male-male competition or influencing the female mate choice, and can be thought of as functioning on three different levels: individuals, colonies, and populations within an area.

An alternative mating strategy is a strategy used by male or female animals, often with distinct phenotypes, that differs from the prevailing mating strategy of their sex. Such strategies are diverse and variable both across and within species. Animal sexual behaviour and mate choice directly affect social structure and relationships in many different mating systems, whether monogamous, polygamous, polyandrous, or polygynous. Though males and females in a given population typically employ a predominant reproductive strategy based on the overarching mating system, individuals of the same sex often use different mating strategies. Among some reptiles, frogs and fish, large males defend females, while small males may use sneaking tactics to mate without being noticed.

In ecology, contest competition refers to a situation where available resources, such as food and mates, are utilized only by one or a few individuals, thus preventing development or reproduction of other individuals. It refers to a hypothetical situation in which several individuals stage a contest for which one eventually emerges victorious. Contest competition is the opposite of scramble competition, a situation in which available resources are shared equally among individuals.

<span class="mw-page-title-main">Primate sociality</span>

Primate sociality is an area of primatology that aims to study the interactions between three main elements of a primate social network: the social organisation, the social structure and the mating system. The intersection of these three structures describe the socially complex behaviours and relationships occurring among adult males and females of a particular species. Cohesion and stability of groups are maintained through a confluence of factors, including: kinship, willingness to cooperate, frequency of agonistic behaviour, or varying intensities of dominance structures.

References

  1. 1 2 3 4 Den Berg, V., Rossing, W., and Grasman, J. (2006). "Contest and Scramble Competition and the Carry-Over Effect in Globodera spp. In Potato-Based Crop Rotations Using an Extended Ricker Model". Journal of Nematology, 38(2):210-220.
  2. 1 2 "Competition" (PDF). Heying. 2004. Retrieved February 22, 2011.
  3. 1 2 "Intraspecific Competition and Social Systems". loki.stockton.edu. Retrieved February 22, 2011.
  4. 1 2 3 4 5 Berryman, Alan (1997). "Intraspecific Competition". classes.entom.wsu.edu. Retrieved February 22, 2011.
  5. 1 2 3 Rank, N. E.; Yturralde, K.; Dahlhoff, E. P. (2006). "Role of Contests in the Scramble Competition Mating System of a Leaf Beetle". Journal of Insect Behavior. 19 (6): 699. CiteSeerX   10.1.1.419.6609 . doi:10.1007/s10905-006-9051-2. S2CID   5267930.
  6. 1 2 Sharov, Alexei (1997). "11.1 Intra-specific Competition". ma.utexas.edu. Retrieved February 22, 2011.
  7. ↑ Brännström, A.; Sumpter, DJT (2005). "The role of competition and clustering in population dynamics" (PDF). Proceedings of the Royal Society of London B: Biological Sciences. 272 (1576): 2065–2072. doi:10.1098/rspb.2005.3185. PMC   1559893 . PMID   16191618.
  8. ↑ "Polygyny". faculty.vassar.edu. Retrieved February 22, 2011.
  9. ↑ "Social Relationships". life.bio.sunysb.edu. Retrieved February 22, 2011.
  10. 1 2 Able, D. (1999). "Scramble competition selects for greater tailfin size in male red-spotted news (Amphibia:Salmandriade)" Behavior Ecological Sociobiological 46: 423-428.
  11. 1 2 MoyaLarano, J., Tigani El-Sayyid, M., and Fox, C. (2007). "Smaller beetles are better scramble competitors at cooler temperatures". Biol Lett. 22; 3(5): 475-478.
  12. ↑ Davies, N., Krebs, J., & West, S. (2012). An introduction to behavioral ecology. (4th ed.). West Sussex, UK: Wiley-Blackwell.
  13. ↑ Łomnicki, A. (2008-01-01), "Competition and Behavior", in Jørgensen, Sven Erik; Fath, Brian D. (eds.), Encyclopedia of Ecology, Oxford: Academic Press, pp. 695–700, ISBN   978-0-08-045405-4 , retrieved 2020-12-14
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