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In ecology, a niche is the match of a species to a specific environmental condition. It describes how an organism or population responds to the distribution of resources and competitors and how it in turn alters those same factors. "The type and number of variables comprising the dimensions of an environmental niche vary from one species to another [and] the relative importance of particular environmental variables for a species may vary according to the geographic and biotic contexts".
The tits, chickadees, and titmice constitute the Paridae, a large family of small passerine birds which occur mainly in the Northern Hemisphere and Africa. Most were formerly classified in the genus Parus.
In ecology, the competitive exclusion principle, sometimes referred to as Gause's law, is a proposition that two species which compete for the same limited resource cannot coexist at constant population values. When one species has even the slightest advantage over another, the one with the advantage will dominate in the long term. This leads either to the extinction of the weaker competitor or to an evolutionary or behavioral shift toward a different ecological niche. The principle has been paraphrased in the maxim "complete competitors can not coexist".
Character displacement is the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species' distributions do not overlap. This pattern results from evolutionary change driven by biological competition among species for a limited resource. The rationale for character displacement stems from the competitive exclusion principle, also called Gause's Law, which contends that to coexist in a stable environment two competing species must differ in their respective ecological niche; without differentiation, one species will eliminate or exclude the other through competition.
In ecological theory, the Hutchinson's ratio is the ratio of the size differences between similar species when they are living together as compared to when they are isolated. It is named after G. Evelyn Hutchinson who concluded that various key attributes in species varied according to the ratio of 1:1.1 to 1:1.4.
In ecology, niche differentiation refers to the process by which competing species use the environment differently in a way that helps them to coexist. The competitive exclusion principle states that if two species with identical niches compete, then one will inevitably drive the other to extinction. This rule also states that two species cannot occupy the same exact niche in a habitat and coexist together, at least in a stable manner. When two species differentiate their niches, they tend to compete less strongly, and are thus more likely to coexist. Species can differentiate their niches in many ways, such as by consuming different foods, or using different areas of the environment.
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.
The issue of what exactly defines a vacant niche, also known as empty niche, and whether they exist in ecosystems is controversial. The subject is intimately tied into a much broader debate on whether ecosystems can reach equilibrium, where they could theoretically become maximally saturated with species. Given that saturation is a measure of the number of species per resource axis per ecosystem, the question becomes: is it useful to define unused resource clusters as niche 'vacancies'?
Species use restricted ecological niches, and the niches of all species are segregated, often with much overlap, by the use of different habitats, different geographic areas and seasons, and different food resources, to mention only a few of the many niche dimensions. The causes of niche restriction and segregation are important problems in evolutionary ecology.
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.
In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community, or life assemblage. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization".
Source–sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect the population growth or decline of organisms.
In aquatic biology, the paradox of the plankton describes the situation in which a limited range of resources supports an unexpectedly wide range of plankton species, apparently flouting the competitive exclusion principle which holds that when two species compete for the same resource, one will be driven to extinction.
In ecology, the occupancy–abundance (O–A) relationship is the relationship between the abundance of species and the size of their ranges within a region. This relationship is perhaps one of the most well-documented relationships in macroecology, and applies both intra- and interspecifically. In most cases, the O–A relationship is a positive relationship. Although an O–A relationship would be expected, given that a species colonizing a region must pass through the origin and could reach some theoretical maximum abundance and distribution, the relationship described here is somewhat more substantial, in that observed changes in range are associated with greater-than-proportional changes in abundance. Although this relationship appears to be pervasive, and has important implications for the conservation of endangered species, the mechanism(s) underlying it remain poorly understood
Community assembly rules are a set of controversial rules in ecology, first proposed by Jared Diamond.
The body size-species richness distribution is a pattern observed in the way taxa are distributed over large spatial scales. The number of species that exhibit small body size generally far exceed the number of species that are large-bodied. Macroecology has long sought to understand the mechanisms that underlie the patterns of biodiversity, such as the body size-species richness pattern.
Limiting similarity is a concept in theoretical ecology and community ecology that proposes the existence of a maximum level of niche overlap between two given species that will allow continued coexistence.
The geographical limits to the distribution of a species are determined by biotic or abiotic factors. Core populations are those occurring within the centre of the range, and marginal populations are found at the boundary of the range.
Coexistence theory is a framework to understand how competitor traits can maintain species diversity and stave-off competitive exclusion even among similar species living in ecologically similar environments. Coexistence theory explains the stable coexistence of species as an interaction between two opposing forces: fitness differences between species, which should drive the best-adapted species to exclude others within a particular ecological niche, and stabilizing mechanisms, which maintains diversity via niche differentiation. For many species to be stabilized in a community, population growth must be negative density-dependent, i.e. all participating species have a tendency to increase in density as their populations decline. In such communities, any species that becomes rare will experience positive growth, pushing its population to recover and making local extinction unlikely. As the population of one species declines, individuals of that species tend to compete predominantly with individuals of other species. Thus, the tendency of a population to recover as it declines in density reflects reduced intraspecific competition (within-species) relative to interspecific competition (between-species), the signature of niche differentiation.
Ontogenetic niche shift is an ecological phenomenon where an organism changes its diet or habitat during its ontogeny (development). During the ontogenetic niche shifting an ecological niche of an individual changes its breadth and position. The best known representatives of taxa that exhibit some kind of the ontogenetic niche shift are fish, insects and amphibians. A niche shift is thought to be determined genetically, while also being irreversible. Important aspect of the ONS is the fact, that individuals of different stages of a population utilize different kind of resources and habitats. The term was introduced in a 1984 paper by biologists Earl E. Werner and James F. Gilliam.
References
- ↑ Hutchinson, G. E.; MacArthur, Robert H. (March 1959). "A Theoretical Ecological Model of Size Distributions Among Species of Animals". The American Naturalist. 93 (869): 117–125. doi:10.1086/282063. S2CID 84614449.
- ↑ Broekhoven, Louis; Colgan, Patrick (January 1987). "Size Ratios and Artifacts: Hutchinson's Rule Revisited". The American Naturalist. 129 (1): 1–17. doi:10.1086/284619. S2CID 84663662.
- ↑ Gotelli, Nicholas; Graves, Gary. "Null models in ecology 1996".
{{cite journal}}: Cite journal requires|journal=(help) - ↑ Alatalo, Rauno V.; Gustafsson, Lars; Lundberg, Arne (June 1986). "Interspecific Competition and Niche Changes in Tits (Parus spp.): Evaluation of Nonexperimental Data". The American Naturalist. 127 (6): 819–834. doi:10.1086/284527. S2CID 83789361.
- ↑ Eadie, John McA.; Broekhoven, Louis; Colgan, Patrick (1987). "Size Ratios and Artifacts: Hutchinson's Rule Revisited". The American Naturalist. 129 (1): 1–17. doi:10.1086/284619. JSTOR 2461961. S2CID 84663662.
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