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[[File:Bear predation on salmon can be high in many Alaskan rivers.jpg|right|thumb|
In ecology, a '''community'''
'''Community ecology''' or '''synecology''' is the study of the interactions between species in communities on many spatial and temporal scales, including the distribution, structure, abundance, [[demography]], and [[biological interaction|interaction]]s
Community ecology also takes into account [[Abiotic components|
On a deeper level the meaning and value of the community concept in ecology is up for debate. Communities have traditionally been understood on a fine scale in terms of local processes constructing (or destructing) an assemblage of species, such as the way climate change is likely to affect the make-up of grass communities.<ref>{{cite journal | author = Grime J. P. | year = 2008 | title = Long-term resistance to simulated climate change in an infertile grassland | journal = PNAS | volume = 105 | issue = 29| pages = 10028–10032 | doi=10.1073/pnas.0711567105|display-authors=etal | pmid=18606995 | pmc=2481365| bibcode = 2008PNAS..10510028G | doi-access = free }}</ref> Recently this local community focus has been
==Organization==
▲On a deeper level the meaning and value of the community concept in ecology is up for debate. Communities have traditionally been understood on a fine scale in terms of local processes constructing (or destructing) an assemblage of species, such as the way climate change is likely to affect the make-up of grass communities.<ref>{{cite journal | author = Grime J. P. | year = 2008 | title = Long-term resistance to simulated climate change in an infertile grassland | journal = PNAS | volume = 105 | issue = 29| pages = 10028–10032 | doi=10.1073/pnas.0711567105|display-authors=etal | pmid=18606995 | pmc=2481365| bibcode = 2008PNAS..10510028G }}</ref> Recently this local community focus has been criticised. [[Robert Ricklefs]] has argued that it is more useful to think of communities on a regional scale, drawing on evolutionary [[Taxonomy (biology)|taxonomy]] and [[biogeography]],<ref name="Sahney Benton 2008"/> where some species or [[clade]]s evolve and others go extinct.<ref>{{cite journal | author = Ricklefs R.E. | year = 2008 | title = Disintegration of the Ecological Community | url = | journal = American Naturalist | volume = 172 | issue = 6| pages = 741–750 | pmid = 18954264 | doi=10.1086/593002}}</ref>
===Niche===
Within the community, each species occupies a [[Ecological niche|niche]]. A species' niche determines how it interacts with the environment around it and its role within the community. By having different niches species are able to coexist.<ref>{{cite journal |last1=Albrecht |first1=M. |last2=Gotelli |first2=N.J. |title=Spatial and temporal niche partitioning in grassland ants |journal=Oecologia |date=2001 |volume=126 |issue=1 |pages=134–141 |doi=10.1007/s004420000494|pmid=28547432 |bibcode=2001Oecol.126..134A |s2cid=5236696 }}</ref> This is known as niche partitioning. For example, the time of day a species hunts or the prey it hunts.
Niche partitioning
The number of niches present in a community determines the number of species present. If two species have the
===Trophic
[[File:TrophicWeb.jpg|thumb
A
A basic example of a food chain is;
The trophic level of an organism can change based on the other species present. For example, tuna can be an apex predator eating the smaller fish, such as mackerel. However, in a community where a shark species is present the shark becomes the apex predator, feeding on the tuna.
[[Decomposers]] play a role in the trophic pyramid. They provide energy source and nutrients to the plant species in the community. Decomposers such as fungi and bacteria recycle energy back to the base of the food web by feeding on dead organisms from all trophic levels.
===Guild===
A [[
Carnivores,
==Influential species==
Certain species have a greater influence on the community through their direct and indirect interactions with other species. The population of influential species are affected by abiotic and biotic disturbances. These species are important in identifying communities of ecology. The loss of these species results in large changes to the community, often reducing the stability of the community. Climate change and the introduction of invasive species can affect the functioning of key species and thus have knock
===Foundation species===
[[Foundation species]] largely influence the population, dynamics and processes of a community, by creating physical changes to the environment itself.<ref>{{Cite web |title=Species with a Large Impact on Community Structure {{!}} Learn Science at Scitable |url=https://www.nature.com/scitable/knowledge/library/species-with-a-large-impact-on-community-13240710/ |access-date=2023-02-16 |website=www.nature.com |language=en}}</ref> These species can occupy any trophic level, but tend to be producers.
Whitebark pine (''[[Pinus albicaulis]]'') is a foundation species. Post fire disturbance the tree provides shade (due to its dense growth) enabling the regrowth of other plant species in the community, This growth prompts the return of invertebrates and microbes
[[File:Trophic Cascade.svg|thumb|
▲[[File:Trophic Cascade.svg|thumb|400px | A simple trophic cascade diagram. On the left shows when wolves are absent, showing an increase in elks and reduction in vegetation growth. The right shows when wolves are present and controlling the elk population. ]]
===Keystone species===
[[Keystone species]] have a disproportionate influence on the community than most species. Keystone species tend to be at the higher trophic levels, often being the apex predator. Removal of the keystone species causes top-down [[
In [[Yellowstone National Park]] the loss of the wolf population through overhunting resulted in the [[loss of biodiversity]] in the community. The wolves had controlled the number of [[
A marine example of a keystone species is ''[[Pisaster ochraceus]]''. This starfish controls the abundance of ''[[Mytilus californianus]]'', allowing enough resources for the other species in the community.
===Ecological engineers===
An [[
Dam building beavers are ecological engineers. Through the cutting of trees to form dams they alter the flow of water in a community. These changes influence the vegetation on the [[
==Theories of community structure==
Community structure is the composition of the community. It
===Holistic theory===
Holistic theory refers to the idea that a community is defined by the interactions between the organisms in it. All species are interdependent, each playing a vital role in the working of the community. Due to this communities are repeatable and easy to identify, with similar abiotic factors controlling throughout.
[[Frederic
The Holistic theory stems from the greater thinking of [[Holism]]
===Individualistic theory===
[[Henry A. Gleason (botanist)|Henry Gleason]] developed the individualistic (also known as open or continuum) concept of community, with the abundance of a population of a species changing gradually along complex environmental gradients.<ref>{{cite encyclopedia|doi=10.1093/obo/9780199830060-0042|title=Community Ecology|date=23 May 2012|last1=Verhoef|first1=Herman A.|encyclopedia=Oxford Bibliographies|isbn=978-0-19-983006-0}}</ref> Each species changes independently in relation to other species present along the gradient.<ref>{{cite web|title=What is vegetation classification?|url=https://sites.google.com/site/vegclassmethods/concepts|publisher=International Association for Vegetation Science (IAVS)|
Individualistic theory proposes that communities can exist as continuous entities, in addition to the discrete groups referred to in the holistic theory.
===Neutral theory===
[[Stephen P.
Equivalence of the species in the community leads to ecological drift. Ecological drift leads to species' populations randomly fluctuating, whilst the overall number of individuals in the community remains constant.
When an individual dies, there is an equal chance of each species colonising that plot. Stochastic changes can cause species within the community to go extinct, however, this can take a long time if there are many individuals of that species.
Species can coexist because they are similar, resources and conditions apply a filter to the type of species that are present in the community. Each population has the same [[adaptive value]] (competitive and dispersal abilities) and resources demand. Local and regional composition represent a balance between [[
==Interspecific interactions==
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===Competition===
{{Main|Competition (biology)}}
Species can [[Competition (biology)|compete]] with each other for finite [[Resource (biology)|resources]]. It is considered
# '''Interference competition''': occurs when an individual of one species directly interferes with an individual of another species. This can be for food or for territory. Examples include a lion chasing a hyena from a kill, or a plant releasing [[allelopathic]] chemicals to impede the growth of a competing species.
# '''Apparent competition''': occurs when two species share a predator. For example, a cougar preys on woodland caribou and deer. The populations of both species can be depressed by predation without direct exploitative competition.<ref>{{cite journal | author = Holt R.D. | year = 1977 | title = Predation, apparent competition, and the structure of prey communities
[[File:Prey symmetric.png # '''Exploitative competition''': This occurs via the consumption of resources. When an individual of one species consumes a resource (e.g., food, shelter, sunlight, etc.), that resource is no longer available
::*[[size-asymmetric competition|complete symmetric]] - all individuals receive the same amount of resources, irrespective of their size
::*perfect size symmetric - all individuals exploit the same amount of resource per unit biomass
::*absolute size-asymmetric - the largest individuals exploit all the available resource.
::The degree of size asymmetry has major effects on the structure and diversity of ecological communities
===Predation===
{{Main|Predation}}
[[Predation]] is hunting another species for food. This is a
Other predators are parasites that feed on prey while alive, for example, a vampire bat feeding on a cow. Parasitism can however lead to death of the host organism over time.
Another example is the feeding on plants of [[herbivore]]s, for example, a cow grazing. Herbivory is a type of predation in which a plant (the prey in this example) will attempt to dissuade the predator from eating the plant by pumping a toxin to the plant leaves. This may cause the predator to consume other areas of the plant or not consume the plant at all.<ref>{{Cite journal |last1=Lehman |first1=Clarence |last2=Loberg |first2=Shelby |last3=Clark |first3=Adam T |last4=Schmitter |first4=Daniel |date=2020-04-22 |title=Unifying the Basic Models of Ecology to Be More Complete and Easier to Teach |journal=BioScience |volume=70 |issue=5 |pages=415–426 |doi=10.1093/biosci/biaa013 |issn=0006-3568|doi-access=free }}</ref>
Predation may affect the population size of predators and prey and the number of species coexisting in a community.
Predation can be specialist, for example the least weasel predates solely on the field vole. Or generalist, e.g. polar bear primarily eats seals but can switch diet to birds when seal population is low.
Species can be solitary or group predators.
[[File:Predator prey curve.png|thumb|right|A generalised graph of a predator-prey population density cycle
Predation is '''density dependant''', often leading to population cycles. When prey is abundant predator species increases, thus eating more prey species and causing the prey population to decline. Due to lack of food the predator population declines. Due to lack of predation the prey population increases. See [[Lotka–Volterra equations]] for more details on this. A well-known example of this is [[Canada lynx|
Predation can result in '''coevolution''' – [[
===Mutualism===
{{Main|Mutualism (biology)}}
[[Mutualism (biology)|Mutualism]] is an interaction between species in which both species benefit. An example is ''[[Rhizobium]]'' bacteria growing in nodules on the roots of legumes. This relationship between plant and bacteria is [[Endosymbiont|
Insects pollinating the flowers of [[angiosperm]]s, is another example. Many plants are dependent on [[
===Commensalism===
{{Main|Commensalism}}
[[Commensalism]] is a type of relationship among organisms in which one organism benefits while the other organism is neither benefited nor harmed. The organism that benefited is called the ''commensal'' while the other organism that is neither benefited nor harmed is called the ''host''.
For example, an [[epiphyte|epiphytic]] orchid attached to the tree for support benefits the orchid but neither harms nor benefits the tree. This type of commensalism is called '''[[
'''[[Phoresy]]''' is another type of commensalism, the commensal uses the host solely for transport. Many [[
'''Metabiosis''' is the final form of commensalism. The commensal relies on the host to prepare an environment suitable for life. For example, Kelp has a root like system, called a [[
===Amensalism===
{{Main|Amensalism}}
The opposite of commensalism is [[amensalism]], an interspecific relationship in which a product of one organism has a negative effect on another organism but the original organism is unaffected.<ref>{{cite book|author1=Willey, Joanne M. |author2=Sherwood, Linda M. |author3=Woolverton Cristopher J. |title=Microbiology|year=2011|publisher=Prescott's|pages=713–738}}</ref>
An example is
An older, taller tree can inhibit the growth of smaller trees. A new sapling growing in the shade of a mature tree
=== Parasitism ===
{{Main|Parasitism}}
[[Parasitism]] is an interaction in which one organism, the host, is harmed while the other, the parasite, benefits.
Parasitism is a
[[File:Piet-my-vrou & cape robin.jpg|thumb|
[[Malaria]] is a result of a parasitic relationship between a female [[Anopheles mosquito]] and
Mosquitos get the parasite by feeding on an infected vertebrate. Inside the mosquito the plasmodium develops in the midgut's wall. Once developed to a [[
A second example of parasitism is [[Brood parasite|
[[Cuckoos]] regularly do this type of parasitism. Cuckoos lay their eggs in the nest of another species of birds. The host, therefore, provides for the cuckoo chick as if it
In a similar way to predation, parasitism can lead to an
=== Neutralism ===
{{Main|Neutralism (biological interaction)}}
Neutralism is where species interact, but the interaction has no noticeable effects on either species involved. Due to the interconnectedness of communities, true neutralism is rare. Examples of neutralism in ecological systems are hard to prove, due to the indirect effects that species can have on each other.
==See also==
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* {{Annotated link|Guild (ecology)}}
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==References==
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* Ricklefs, R.E. (2005) ''The Economy of Nature'', 6th ed. WH Freeman, USA.
* Ricketts, Taylor H., Eric Dinerstein, David M. Olson, Colby J. Loucks et al. ([[World Wide Fund for Nature|WWF]]) (1999). ''Terrestrial Ecoregions of North America: a conservation assessment''. Island Press. {{ISBN|1-55963-722-6}}.
* Stefano Allesina's Community Ecology course lecture notes: https://stefanoallesina.github.io/Theoretical_Community_Ecology/
==External links==
* [http://wiki.biomine.skelleftea.se/wiki/index.php/Community Community, BioMineWiki] {{Webarchive|url=https://web.archive.org/web/20210627210416/http://wiki.biomine.skelleftea.se/wiki/index.php/Community |date=27 June 2021 }}
* [http://wiki.biomine.skelleftea.se/wiki/index.php/Identification/Characterization Identify microbial species in a community, BioMineWiki] {{Webarchive|url=https://web.archive.org/web/20210630055503/http://wiki.biomine.skelleftea.se/wiki/index.php/Identification/Characterization |date=30 June 2021 }}
* [https://web.archive.org/web/20070715060359/http://biology.usgs.gov/s+t/SNT/noframe/zy198.htm Glossary], Status and Trends of the Nation's Biological Resources, USGS.
* [http://www.entrix.com/resources/glossary.aspx Glossary], ENTRIX Environmental Consultants.
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