Foundation species

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Californian forest of giant kelp, a foundation species Sanc0063 - Flickr - NOAA Photo Library.jpg
Californian forest of giant kelp, a foundation species

In ecology, the foundation species are species that have a strong role in structuring a community. A foundation species can occupy any trophic level in a food web (i.e., they can be primary producers, herbivores or predators). The term was coined by Paul K. Dayton in 1972, [2] who applied it to certain members of marine invertebrate and algae communities. It was clear from studies in several locations that there were a small handful of species whose activities had a disproportionate effect on the rest of the marine community and they were therefore key to the resilience of the community. Dayton’s view was that focusing on foundation species would allow for a simplified approach to more rapidly understand how a community as a whole would react to disturbances, such as pollution, instead of attempting the extremely difficult task of tracking the responses of all community members simultaneously. The term has since been applied to a range of organisms in ecosystems around the world, in both aquatic and terrestrial environments. Aaron Ellison et al. introduced the term to terrestrial ecology by applying the term foundation species to tree species that define and structure certain forest ecosystems through their influences on associated organisms and modulation of ecosystem processes. [3]

Contents

Examples and outcomes of foundation species loss

Tsuga canadensis Tsuga canadensis morton.jpg
Tsuga canadensis

A study conducted at the McKenzie Flats of the Sevilleta National Wildlife Refuge in New Mexico, a semiarid biome transition zone, observed the result of loss of a variety of different dominant and codominant foundation species of plants on the growth of other species. This transition zone consists of two Chihuahuan Desert species, black grama ( Bouteloua eriopoda) and creosote bush ( Larrea tridentata), and a shortgrass steppe species, blue grama ( Bouteloua gracillis). Each species dominates an area with a specific soil environment. Black grama dominates sandy soils, while blue grama dominates in soils with high clay content, and creosote bush dominates fine-textured soil with surface gravel. This study noted that responses to the loss of foundation species is dependent on a variety of different factors from the ability of a species to recover to the climate conditions of the ecosystem to the patterns in dominance and explored the possible reasons for the outcomes of the study. The results indicated that in areas with just one dominant foundation species, its loss caused a shift in dominance to a mixed dominant community. For example, the creosote bush dominated shrubland saw a shift in dominance to 32% by other shrubs, 26% by perennial grasses, and 22% by perennial forbs following the removal of creosote bush. Another finding was that regardless of the community type and the species removed, the loss of foundation species resulted in an overall increase in black grama supporting the notion that the outcome is greatly affected by recovery ability of species removed or loss. [4]

Another study observed the effects of loss of foundation eastern hemlocks ( Tsuga canadensis ) in a forest ecosystem. [5] Eastern hemlocks are a foundation species in eastern North American forests, but have been threatened by the accidental introduction of woolly adelgid. This study observed the effects that a loss in eastern hemlocks would have on the populations of arthropods, such as ants, beetles, and spiders, since these species are known indicators of environmental change. The results found that in areas of hemlock removal, there was an overall increase and influx of arthropod species. Researchers suggested that this was due to an increase in open habitats from the loss of the hemlocks. The results of this hemlock study corroborated with those from the previous McKenzie Flats study discussed in that the loss of foundation species led to a proliferation of species diversity in the affected area. These results seem to contradict a long-standing belief that foundation species play a vital role in communities and ecosystems by creating habitats for organisms, suggesting that in some circumstances they bottleneck species diversity. [6]

Foundation species play a vital role in structuring a community; however, this can be in a variety of different ways. The presence of a foundation species has the ability to either reduce or increase species diversity depending on its particular role in a specific ecosystem. The studies discussed highlighted examples in which foundation species limited species diversity in similar and differing taxa (the McKenzie Flats and eastern hemlock studies, respectively). [4] [5]

Effects

Foundation species enhance food web complexity
In a 2018 study by Borst et al...
(A) Seven ecosystems with foundation species were sampled: coastal (seagrass, blue mussel, cordgrass), freshwater (watermilfoil, water-starwort) and terrestrial (Spanish moss, marram grass).
(B) Food webs were constructed for both bare and foundation species-dominated replicate areas.
(C) From each foundation species structured-food web, nodes (species) were randomly removed until the species number matched the species number of the bare food webs.

The presence of foundation species strongly enhances food web complexity, facilitating particularly species higher in the food chains. Foundation species enhance food web complexity.png
Foundation species enhance food web complexity
In a 2018 study by Borst et al...
(A) Seven ecosystems with foundation species were sampled: coastal (seagrass, blue mussel, cordgrass), freshwater (watermilfoil, water-starwort) and terrestrial (Spanish moss, marram grass).
(B) Food webs were constructed for both bare and foundation species-dominated replicate areas.
(C) From each foundation species structured-food web, nodes (species) were randomly removed until the species number matched the species number of the bare food webs.

The presence of foundation species strongly enhances food web complexity, facilitating particularly species higher in the food chains.


A 2018 study by Borst et al.. tested the general hypothesis that foundation species – spatially dominant habitat-structuring organisms [8] [9] [10] – modify food webs by enhancing their size as indicated by species number, and their complexity as indicated by link density, via facilitation of species, regardless of ecosystem type (see diagram). [7] Additionally, they tested that any change in food web properties caused by foundation species occurs via random facilitation of species throughout the entire food web or via targeted facilitation of specific species that belong to certain trophic levels or functional groups. It was found that species at the base of the food web are less strongly, and carnivores are more strongly facilitated in foundation species' food webs than predicted based on random facilitation, resulting in a higher mean trophic level and a longer average chain length. This indicates foundation species strongly enhance food web complexity through non-trophic facilitation of species across the entire trophic network. [7]

Foundation species strongly facilitate the associated community by creating new habitat and alleviating physical stress. [11] [12] [13] [14] [15] [16] This form of non-trophic facilitation by foundation species has been found to occur across a wide range of ecosystems and environmental conditions. [17] [18] In harsh coastal zones, corals, kelps, mussels, oysters, seagrasses, mangroves, and salt marsh plants facilitate organisms by attenuating currents and waves, providing aboveground structure for shelter and attachment, concentrating nutrients, and/or reducing desiccation stress during low tide exposure. [8] [18] In more benign systems, foundation species such as the trees in a forest, shrubs and grasses in savannahs, and macrophytes in freshwater systems, have also been found to play a major habitat-structuring role. [17] [18] [19] [20] Ultimately, all foundation species increase habitat complexity and availability, thereby partitioning and enhancing the niche space available to other species. [17] [21] [7]

See also

Related Research Articles

<span class="mw-page-title-main">Ecology</span> Study of organisms and their environment

Ecology is the natural science of the relationships among living organisms and their environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere levels. Ecology overlaps with the closely related sciences of biogeography, evolutionary biology, genetics, ethology, and natural history.

<span class="mw-page-title-main">Food web</span> Natural interconnection of food chains

A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Position in the food web, or trophic level, is used in ecology to broadly classify organisms as autotrophs or heterotrophs. This is a non-binary classification; some organisms occupy the role of mixotrophs, or autotrophs that additionally obtain organic matter from non-atmospheric sources.

<span class="mw-page-title-main">Keystone species</span> Species with a large effect on its environment

A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf and lion, are also apex predators.

<span class="mw-page-title-main">Biological interaction</span> Effect that organisms have on other organisms

In ecology, a biological interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species, or of different species. These effects may be short-term, or long-term, both often strongly influence the adaptation and evolution of the species involved. Biological interactions range from mutualism, beneficial to both partners, to competition, harmful to both partners. Interactions can be direct when physical contact is established or indirect, through intermediaries such as shared resources, territories, ecological services, metabolic waste, toxins or growth inhibitors. This type of relationship can be shown by net effect based on individual effects on both organisms arising out of relationship.

<span class="mw-page-title-main">Energy flow (ecology)</span> Flow of energy through food chains in ecological energetics

Energy flow is the flow of energy through living things within an ecosystem. All living organisms can be organized into producers and consumers, and those producers and consumers can further be organized into a food chain. Each of the levels within the food chain is a trophic level. In order to more efficiently show the quantity of organisms at each trophic level, these food chains are then organized into trophic pyramids. The arrows in the food chain show that the energy flow is unidirectional, with the head of an arrow indicating the direction of energy flow; energy is lost as heat at each step along the way.

<span class="mw-page-title-main">Kelp forest</span> Underwater areas highly dense with kelp

Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on Earth. Although algal kelp forest combined with coral reefs only cover 0.1% of Earth's total surface, they account for 0.9% of global primary productivity. Kelp forests occur worldwide throughout temperate and polar coastal oceans. In 2007, kelp forests were also discovered in tropical waters near Ecuador.

The diversity of species and genes in ecological communities affects the functioning of these communities. These ecological effects of biodiversity in turn are affected by both climate change through enhanced greenhouse gases, aerosols and loss of land cover, and biological diversity, causing a rapid loss of biodiversity and extinctions of species and local populations. The current rate of extinction is sometimes considered a mass extinction, with current species extinction rates on the order of 100 to 1000 times as high as in the past.

<span class="mw-page-title-main">River ecosystem</span> Type of aquatic ecosystem with flowing freshwater

River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts. River ecosystems are part of larger watershed networks or catchments, where smaller headwater streams drain into mid-size streams, which progressively drain into larger river networks. The major zones in river ecosystems are determined by the river bed's gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow-moving water of pools. These distinctions form the basis for the division of rivers into upland and lowland rivers.

<span class="mw-page-title-main">Intertidal ecology</span> Study of ecosystems, where organisms live between the low and high tide lines

Intertidal ecology is the study of intertidal ecosystems, where organisms live between the low and high tide lines. At low tide, the intertidal is exposed whereas at high tide, the intertidal is underwater. Intertidal ecologists therefore study the interactions between intertidal organisms and their environment, as well as between different species of intertidal organisms within a particular intertidal community. The most important environmental and species interactions may vary based on the type of intertidal community being studied, the broadest of classifications being based on substrates—rocky shore and soft bottom communities.

Soil ecology studies interactions among soil organisms, and their environment. It is particularly concerned with the cycling of nutrients, soil aggregate formation and soil biodiversity.

Trophic cascades are powerful indirect interactions that can control entire ecosystems, occurring when a trophic level in a food web is suppressed. For example, a top-down cascade will occur if predators are effective enough in predation to reduce the abundance, or alter the behavior of their prey, thereby releasing the next lower trophic level from predation.

<span class="mw-page-title-main">Community (ecology)</span> Associated populations of species in a given area

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".

<span class="mw-page-title-main">Cross-boundary subsidy</span>

Cross-boundary subsidies are caused by organisms or materials that cross or traverse habitat patch boundaries, subsidizing the resident populations. The transferred organisms and materials may provide additional predators, prey, or nutrients to resident species, which can affect community and food web structure. Cross-boundary subsidies of materials and organisms occur in landscapes composed of different habitat patch types, and so depend on characteristics of those patches and on the boundaries in between them. Human alteration of the landscape, primarily through fragmentation, has the potential to alter important cross-boundary subsidies to increasingly isolated habitat patches. Understanding how processes that occur outside of habitat patches can affect populations within them may be important to habitat management.

An ecological network is a representation of the biotic interactions in an ecosystem, in which species (nodes) are connected by pairwise interactions (links). These interactions can be trophic or symbiotic. Ecological networks are used to describe and compare the structures of real ecosystems, while network models are used to investigate the effects of network structure on properties such as ecosystem stability.

A food chain is a linear network of links in a food web, often starting with an autotroph, also called a producer, and typically ending at an apex predator, detritivore, or decomposer. It is not the same as a food web. A food chain depicts relations between species based on what they consume for energy in trophic levels, and they are most commonly quantified in length: the number of links between a trophic consumer and the base of the chain.

<span class="mw-page-title-main">Planktivore</span> Aquatic organism that feeds on planktonic food

A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Planktivorous organisms encompass a range of some of the planet's smallest to largest multicellular animals in both the present day and in the past billion years; basking sharks and copepods are just two examples of giant and microscopic organisms that feed upon plankton.

<span class="mw-page-title-main">Salt marsh die-off</span> Ecological disaster in low-elevation salt marshes

Salt marsh die-off is a term that has been used in the US and UK to describe the death of salt marsh cordgrass leading to subsequent degradation of habitat, specifically in the low marsh zones of salt marshes on the coasts of the Western Atlantic. Cordgrass normally anchors sediment in salt marshes; its loss leads to decreased substrate hardness, increased erosion, and collapse of creek banks into the water, ultimately resulting in decreased marsh health and productivity.

A habitat cascade is a common type of a facilitation cascade. where “indirect positive effects on focal organisms are mediated by successive formation or modification of biogenic habitat”.

<span class="mw-page-title-main">Marine food web</span> Marine consumer-resource system

A marine food web is a food web of marine life. At the base of the ocean food web are single-celled algae and other plant-like organisms known as phytoplankton. The second trophic level is occupied by zooplankton which feed off the phytoplankton. Higher order consumers complete the web. There has been increasing recognition in recent years that marine microorganisms.

<span class="mw-page-title-main">Facilitation cascade</span> Beneficial ecological chain reaction

A facilitation cascade is a sequence of ecological interactions that occur when a species benefits a second species that in turn has a positive effect on a third species. These facilitative interactions can take the form of amelioration of environmental stress and/or provision of refuge from predation. Autogenic ecosystem engineering species, structural species, habitat-forming species, and foundation species are associated with the most commonly recognized examples of facilitation cascades, sometimes referred to as a habitat cascades. Facilitation generally is a much broader concept that includes all forms of positive interactions including pollination, seed dispersal, and co-evolved commensalism and mutualistic relationships, such as between cnidarian hosts and Symbiodinium in corals, and between algae and fungi in lichens. As such, facilitation cascades are widespread through all of the earth's major biomes with consistently positive effects on the abundance and biodiversity of associated organisms.

References

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