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111-397: For humans, because pioneer species quickly occupy disrupted spaces they are sometimes treated as weeds or nuisance wildlife , such as the common dandelion or stinging nettle . Even though humans have mixed relationships with these plants, these species tend to help improve the ecosystem because they can break up compacted soils and accumulate nutrients that help with a transition back to

222-409: A Gaussian might describe the frequency with which a species ate prey of a certain size, giving a more detailed niche description than simply specifying some median or average prey size. For such a bell-shaped distribution, the position , width and form of the niche correspond to the mean , standard deviation and the actual distribution itself. One advantage in using statistics is illustrated in

333-413: 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 (for example, by growing when resources are abundant, and when predators , parasites and pathogens are scarce) and how it in turn alters those same factors (for example, limiting access to resources by other organisms, acting as

444-447: A storage effect . Species can differentiate their niche via a competition-predation trade-off if one species is a better competitor when predators are absent, and the other is better when predators are present. Defenses against predators, such as toxic compounds or hard shells, are often metabolically costly. As a result, species that produce such defenses are often poor competitors when predators are absent. Species can coexist through

555-727: A certain environment (have overlapping requirement niches) but fundamentally differ the ways that they use (or "impact") that environment. These requirements have repeatedly been violated by nonnative (i.e. introduced and invasive ) species, which often coexist with new species in their nonnative ranges, but do not appear to be constricted these requirements. In other words, contemporary niche theory predicts that species will be unable to invade new environments outside of their requirement (i.e. realized) niche, yet many examples of this are well-documented. Additionally, contemporary niche theory predicts that species will be unable to establish in environments where other species already consume resources in

666-427: A climatic perspective, to explain distribution and abundance. Current predictions on species responses to climate change strongly rely on projecting altered environmental conditions on species distributions. However, it is increasingly acknowledged that climate change also influences species interactions and an Eltonian perspective may be advantageous in explaining these processes. This perspective of niche allows for

777-541: A close association with human activities. Some plants become dominant when introduced into new environments because the animals and plants in their original environment that compete with them or feed on them are absent; in what is sometimes called the "natural enemies hypothesis", plants freed from these specialist consumers may become dominant. An example is Klamath weed , which threatened millions of hectares of prime grain and grazing land in North America after it

888-791: A common weed in European wheat fields, but is now sometimes grown as a garden plant. As pioneer species , weeds begin the process of ecological succession after a disturbance event. The rapid, aggressive growth of weeds rapidly prevents erosion in newly exposed bare soil, and has substantially slowed topsoil loss due to anthropogenic disturbances. It has been suggested that weeds, with their aggressive ability to adapt, could provide humans with vital tools and knowledge for climate change adaptation . Some researchers argue that researching weed species could offer valuable insights for crop breeding, or that weeds themselves hold potential as hardy, climate-change-resistant crops. Adaptable weeds could also be

999-482: A competition-predation trade-off if predators are more abundant when the less defended species is common, and less abundant if the well-defended species is common. This effect has been criticized as being weak, because theoretical models suggest that only two species within a community can coexist because of this mechanism. Two ecological paradigms deal with the problem. The first paradigm predominates in what may be called "classical" ecology. It assumes that niche space

1110-440: A crop, because their presence disrupts the incidence of positive cues which pests use to locate their food. Weeds may also act as a "living mulch", providing ground cover that reduces moisture loss and prevents erosion. Weeds may also improve soil fertility; dandelions, for example, bring up nutrients like calcium and nitrogen from deep in the soil with their tap root, and clover hosts nitrogen-fixing bacteria in its roots, fertilizing

1221-472: A food source for predators and a consumer of prey). "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". A Grinnellian niche is determined by the habitat in which a species lives and its accompanying behavioral adaptations . An Eltonian niche emphasizes that

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1332-412: A fundamental niche of the entire slope of a hillside, but its realized niche is only the top portion of the slope because species Y, which is a better competitor but cannot survive on the top portion of the slope, has excluded it from the lower portion of the slope. With this scenario, competition will continue indefinitely in the middle of the slope between these two species. Because of this, detection of

1443-480: A given species), 'niche partitioning' (resource differentiation by coexisting species), and 'niche overlap' (overlap of resource use by different species). Statistics were introduced into the Hutchinson niche by Robert MacArthur and Richard Levins using the 'resource-utilization' niche employing histograms to describe the 'frequency of occurrence' as a function of a Hutchinson coordinate. So, for instance,

1554-463: A more mature ecosystem. In human managed ecological restoration or agroforestry , trees and herbaceous pioneers can be used to restore soil qualities and provide shelter for slower growing or more demanding plants. Some systems use introduced species to restore the ecosystem, or for environmental remediation . The durability of pioneer species can also make them potential invasive species . Some lichens grow on rocks without soil, so may be among

1665-562: A mosaic of different habitats. Vertebrates can affect early seral stages. Herbivores may alter plant growth. Fossorial mammals could alter soil and plant community development. In a profound example, a seabird colony transfers considerable nitrogen into infertile soils, thereby altering plant growth. A keystone species may facilitate the introduction of pioneer species by creating new niches . For example, beavers may flood an area, allowing new species to immigrate. The concept of ecologic succession also applies to underwater habitats. If

1776-551: A negative connotation, many plants known as weeds can have beneficial properties. A number of weeds, such as the dandelion ( Taraxacum ) and lamb's quarter , are edible, and their leaves or roots may be used for food or herbal medicine . Burdock is common over much of the world, and is sometimes used to make soup and medicine in East Asia . Some weeds attract beneficial insects , which in turn can protect crops from harmful pests. Weeds can also prevent pest insects from finding

1887-465: A niche specific to each species. Species can however share a 'mode of life' or 'autecological strategy' which are broader definitions of ecospace. For example, Australian grasslands species, though different from those of the Great Plains grasslands, exhibit similar modes of life. Once a niche is left vacant, other organisms can fill that position. For example, the niche that was left vacant by

1998-425: A plant that is a weed in one context, is not a weed when growing in a situation where it is wanted. Some plants that are widely regarded as weeds are intentionally grown in gardens and other cultivated settings. For this reason, some plants are sometimes called beneficial weeds . Similarly, volunteer plants from a previous crop are regarded as weeds when growing in a subsequent crop. Thus, alternative nomenclature for

2109-586: A powerful influence on the growth of pioneer species. Some examples of the plants in such areas include: Weed A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals. Plants with characteristics that make them hazardous, aesthetically unappealing, difficult to control in managed environments, or otherwise unwanted in farm land , orchards , gardens , lawns , parks , recreational spaces, residential and industrial areas, may all be considered weeds. The concept of weeds

2220-411: A region where there are few natural controls to limit their population and spread. In a range of contexts, weeds can have negative impacts by: "What would the world be, once bereft, of wet and wildness? Let them be left. O let them be left; wildness and wet; Long live the weeds and the wilderness yet." — Gerard Manley Hopkins' poem Inversnaid While the term "weed" generally has

2331-532: A scenario sometimes called the "novel weapons hypothesis". These chemicals may limit the growth of established plants or the germination and growth of seeds and seedlings. Weed growth can also inhibit the growth of later-successional species in ecological succession . Introduced species have been observed to undergo rapid evolutionary change to adapt to their new environments, with changes in plant height, size, leaf shape, dispersal ability, reproductive output, vegetative reproduction ability, level of dependence on

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2442-455: A source of transgenic genes which could confer useful traits upon crops. Weed species have been used in the restoration of land in Australia using a method called natural sequence farming. This method allows non-native weeds to stabilize and restore degraded areas where native species are not yet capable of regenerating themselves. "We've got to be one of the most bomb-proof species on

2553-447: A space becomes newly available in a reef surrounding, haplosclerid and calcareous sponges are the first animals to initially occur in this environment in greater numbers than other species. These types of sponges grow faster and have a shorter life-span than the species which follow them in this habitat. The term pioneer species is also used to refer to the first species, usually plants, to return to an area after disturbance as part of

2664-460: A species not only grows in and responds to an environment, it may also change the environment and its behavior as it grows. The Hutchinsonian niche uses mathematics and statistics to try to explain how species coexist within a given community. The concept of ecological niche is central to ecological biogeography , which focuses on spatial patterns of ecological communities. "Species distributions and their dynamics over time result from properties of

2775-487: A species' density declines, then the food it most depends on will become more abundant (since there are so few individuals to consume it). As a result, the remaining individuals will experience less competition for food. Although "resource" generally refers to food, species can partition other non-consumable objects, such as parts of the habitat. For example, warblers are thought to coexist because they nest in different parts of trees. Species can also partition habitat in

2886-451: A way that gives them access to different types of resources. As stated in the introduction, anole lizards appear to coexist because each uses different parts of the forests as perch locations. This likely gives them access to different species of insects. Research has determined that plants can recognize each other's root systems and differentiate between a clone, a plant grown from the same mother plants seeds, and other species. Based on

2997-478: A weed species. Like other weedy species, humans are widely dispersed in a wide variety of environments, and are highly unlikely to go extinct no matter how much damage the environment faces. White clover is considered by some to be a weed in lawns, but in many other situations is a desirable source of fodder, honey and soil nitrogen. A short list of some plants that often are considered to be weeds follows: Many invasive weeds were introduced deliberately in

3108-400: A weed. Many weed species have moved out of their natural geographic ranges and spread around the world in tandem with human migrations and commerce. Weed seeds are often collected and transported with crops after the harvesting of grains , so humans are a vector of transport as well as a producer of the disturbed environments to which weed species are well adapted, resulting in many weeds having

3219-511: Is absent or low, and therefore detection of niche differentiation is difficult or impossible. Below is a list of ways that species can partition their niche. This list is not exhaustive, but illustrates several classic examples. Resource partitioning is the phenomenon where two or more species divides out resources like food, space, resting sites etc. to coexist. For example, some lizard species appear to coexist because they consume insects of differing sizes. Alternatively, species can coexist on

3330-667: Is also observed to be strongly selected for among some invasive populations, such as Solidago canadensis in China . Many weed species are now found almost worldwide, with novel adaptations that suit regional populations to their environments. Some negative impacts of weeds are functional: they interfere with food and fiber production in agriculture , wherein they must be controlled to prevent lost or diminished crop yields. In other settings, they interfere with other cosmetic, decorative, or recreational goals, such as in lawns , landscape architecture , playing fields , and golf courses . In

3441-548: Is constrained by different natural enemies, they will be able to coexist. Early work focused on specialist predators; however, more recent studies have shown that predators do not need to be pure specialists, they simply need to affect each prey species differently. The Janzen–Connell hypothesis represents a form of predator partitioning. Conditional differentiation (sometimes called temporal niche partitioning ) occurs when species differ in their competitive abilities based on varying environmental conditions. For example, in

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3552-481: Is greater than inter-specific (between species) competition. Since niche differentiation concentrates competition within-species, due to a decrease in between-species competition, the Lotka-Volterra model predicts that niche differentiation of any degree will result in coexistence. In reality, this still leaves the question of how much differentiation is needed for coexistence. A vague answer to this question

3663-507: Is important in agriculture and horticulture . Methods include hand cultivation with hoes , powered cultivation with cultivators , smothering with mulch or soil solarization , lethal wilting with high heat, burning, or chemical attack with herbicides and cultural methods such as crop rotation and fallowing land to reduce the weed population. It has long been assumed that weeds, in the sense of rapidly-evolving plants taking advantage of human-disturbed environments, evolved in response to

3774-489: Is largely saturated with individuals and species, leading to strong competition. Niches are restricted because "neighbouring" species, i.e., species with similar ecological characteristics such as similar habitats or food preferences, prevent expansion into other niches or even narrow niches down. This continual struggle for existence is an important assumption of natural selection introduced by Darwin as an explanation for evolution. The other paradigm assumes that niche space

3885-455: Is merely the product of the competitive exclusion principle. Also, because no species is out-competing any other species in the final community, the presence of niche differentiation will be difficult or impossible to detect. Finally, niche differentiation can arise as an evolutionary effect of competition. In this case, two competing species will evolve different patterns of resource use so as to avoid competition. Here too, current competition

3996-405: Is necessary for ecologists to be able to detect, measure, and quantify the niches of different coexisting and competing species. This is often done through a combination of detailed ecological studies, controlled experiments (to determine the strength of competition), and mathematical models . To understand the mechanisms of niche differentiation and competition, much data must be gathered on how

4107-413: Is often available in the early stages of succession , thus making it less likely for a pioneer species to be non-photosynthetic. The plants that are often pioneer species also tend to be wind-pollinated rather than insect-pollinated , as insects are unlikely to be present in the usually barren conditions in which pioneer species grow; however, pioneer species tend to reproduce asexually altogether, as

4218-442: Is often made out to be. Some people find in it a kind of soothing monotony. It leaves their minds free to develop the plot for their next novel or to perfect the brilliant repartee with which they should have encountered a relative's latest example of unreasonableness. As anthropogenic climate change increases temperatures and atmospheric carbon dioxide, many weeds are expected to become harder to control and to expand their ranges, at

4329-412: Is particularly difficult to counteract, since it may confer resistance to multiple herbicides at once, including herbicides the plants' ancestors were never exposed to. Various methods of adjusting herbicide application to avoid resistance, such as rotating herbicides used and tank mixing herbicides, have all been questioned in terms of their efficacy for preventing resistance from arising. Understanding

4440-410: Is particularly significant in agriculture , where the presence of weeds in fields used to grow crops may cause major losses in yields. Invasive species , plants introduced to an environment where their presence negatively impacts the overall functioning and biodiversity of the ecosystem, may also sometimes be considered weeds. Taxonomically , the term "weed" has no botanical significance, because

4551-416: Is that for much of human history, women and children were an abundant source of cheap labor to control weeds, and not directly acknowledged. Weeds are assumed to have existed since the beginning of agriculture, and accepted as an "inevitable nuisance." Though the plants are not named using a specific term denoting a "weed" in the contemporary sense, plants that may be interpreted as "weeds" are referenced in

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4662-419: Is that the more similar two species are, the more finely balanced the suitability of their environment must be in order to allow coexistence. There are limits to the amount of niche differentiation required for coexistence, and this can vary with the type of resource, the nature of the environment, and the amount of variation both within and between the species. To answer questions about niche differentiation, it

4773-425: Is the niche that is filled by birds of prey which eat small animals such as shrews and mice. In an oak wood this niche is filled by tawny owls , while in the open grassland it is occupied by kestrels . The existence of this carnivore niche is dependent on the further fact that mice form a definite herbivore niche in many different associations, although the actual species of mice may be quite different. Conceptually,

4884-432: Is to a large degree vacant, i.e., that there are many vacant niches . It is based on many empirical studies and theoretical investigations especially of Kauffman 1993. Causes of vacant niches may be evolutionary contingencies or brief or long-lasting environmental disturbances. Both paradigms agree that species are never "universal" in the sense that they occupy all possible niches; they are always specialized, although

4995-458: The Bible : Cursed is the ground because of you; through painful toil you will eat of it all the days of your life. It will produce thorns and thistles for you, and you will eat the plants of the field. By the sweat of your brow you will eat your food until you return to the ground. Some early Roman writers referenced weeding activities in agricultural fields, but weed control in the pre-modern era

5106-588: The Neolithic agricultural revolution approximately 12,000 years ago. However, researchers have found evidence of "proto-weeds" behaving in similar ways at Ohalo II , a 23,000-year-old archeological site in Israel . The idea of "weeds" as a category of undesirable plant has not been universal throughout history. Before 1200 A.D., little evidence exists of concern with weed control or of agricultural practices solely intended to control weeds. A possible reason for this

5217-553: The Sonoran Desert , some annual plants are more successful during wet years, while others are more successful during dry years. As a result, each species will have an advantage in some years, but not others. When environmental conditions are most favorable, individuals will tend to compete most strongly with member of the same species. For example, in a dry year, dry-adapted plants will tend to be most limited by other dry-adapted plants. This can help them to coexist through

5328-464: The common pigeon , brown rat and the raccoon . Other weedy species have been able to expand their range without actually living in human environments, as human activity has damaged the ecosystems of other species. These include the coyote , the white-tailed deer and the brown headed cowbird . In response to the idea that humans may face extinction due to environmental degradation , paleontologist David Jablonsky counters by arguing that humans are

5439-436: The mycorrhizal network , and level of phenotype plasticity appearing on timescales of decades to centuries. Invasive species can be more adaptable in their new environments than in their native environments, occupying broader ranges in areas where they are invasive than in areas where they are native. Hybridization between similar species can produce novel invasive plants that are better adapted to their surroundings. Polyploidy

5550-749: The soil seed bank for many years. Perennial weeds often have underground stems that spread under the soil surface or, like ground ivy ( Glechoma hederacea ), have creeping stems that root and spread out over the ground. These traits make many disturbance-adapted plants highly successful as weeds. On top of the ability of individual plants to adapt to their conditions, weed populations also evolve much more quickly than older models of evolution account for. Once established in an agricultural setting, weeds have been observed to undergo evolutionary changes to adapt to selective pressures imposed by human management. Some examples include changes in seed dormancy, changes in seasonal life cycles, changes in plant morphology, and

5661-478: The "impact niche" is defined as the combination of effects that a given consumer has on both a). the resources that it uses, and b). the other consumers in the ecosystem. Therefore, the impact niche is equivalent to the Eltonian niche since both concepts are defined by the impact of a given species on its environment. The range of environmental conditions where a species can successfully survive and reproduce (i.e.

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5772-495: The Eltonian niche introduces the idea of a species' response to and effect on the environment. Unlike other niche concepts, it emphasizes that a species not only grows in and responds to an environment based on available resources, predators, and climatic conditions, but also changes the availability and behavior of those factors as it grows. In an extreme example, beavers require certain resources in order to survive and reproduce, but also construct dams that alter water flow in

5883-574: The Hutchinsonian definition of a realized niche) is also encompassed under contemporary niche theory, termed the "requirement niche". The requirement niche is bounded by both the availability of resources as well as the effects of coexisting consumers (e.g. competitors and predators). Contemporary niche theory provides three requirements that must be met in order for two species (consumers) to coexist: These requirements are interesting and controversial because they require any two species to share

5994-580: The Reformation, Christian theology that emphasized the degradation of nature after the Fall of Man , and humankind's role and duty to dominate and subdue nature, became more developed and widespread. Various European writers designated certain plants as "vermin" and "filth," though many plants identified as such were valued by gardeners or by herbalists and apothecaries, and some questioned the idea that any plant could be without purpose or value. Laws mandating

6105-900: The area. Soil fauna, ranging from microscopic protists to larger invertebrates , have a role in soil formation and nutrient cycling . Bacteria and fungi are the most important groups in the breakdown of organic detritus left by primary producing plants such as skeletal soil , moss and algae . Soil invertebrates enhance fungal activity by breaking down detritus. As soil develops, earthworms and ants alter soil characteristics. Worm burrows aerate soil and ant hills alter sediment particle size dispersal, altering soil character profoundly. Though vertebrates in general would not be considered pioneer species, there are exceptions. Natterjack toads are specialists in open, sparsely vegetated habitats which may be at an early seral stage . Wide-ranging generalists visit early succession stage habitats, but are not obligate species of those habitats because they use

6216-460: The case of invasive species , they can be of concern for environmental reasons, when introduced species outcompete native plants and cause broader damage to ecosystem health and functioning. Some weed species have been classified as noxious weeds by government authorities because, if left unchecked, they often compete with native or crop plants or cause harm to livestock . They are often foreign species accidentally or imprudently imported into

6327-649: The control of weeds emerged as early as the seventeenth century; in 1691 a law in New York required the removal of "poysonous and Stincking Weeds" in front of houses. In the nineteenth century, manual labor was used to control weeds in European towns and cities, and chemical methods of weed control emerged. For example, a French journal in 1831 documented a mixture of sulfur, lime and water boiled in an iron cauldron as an effective herbicide to prevent grass from growing among cobblestones. The cultural association between weeds and moral or spiritual degradation persisted into

6438-441: The coordinate system." The niche concept was popularized by the zoologist G. Evelyn Hutchinson in 1957. Hutchinson inquired into the question of why there are so many types of organisms in any one habitat. His work inspired many others to develop models to explain how many and how similar coexisting species could be within a given community, and led to the concepts of 'niche breadth' (the variety of resources or habitats used by

6549-481: The ecological space occupied by a species) is subtly different from the "niche" as defined by Grinnell (an ecological role, that may or may not be actually filled by a species—see vacant niches ). A niche is a very specific segment of ecospace occupied by a single species. On the presumption that no two species are identical in all respects (called Hardin's 'axiom of inequality' ) and the competitive exclusion principle , some resource or adaptive dimension will provide

6660-801: The environment. As an example of niche partitioning, several anole lizards in the Caribbean islands share common diets—mainly insects. They avoid competition by occupying different physical locations. Although these lizards might occupy different locations, some species can be found inhabiting the same range, with up to 15 in certain areas. For example, some live on the ground while others are arboreal. Species who live in different areas compete less for food and other resources, which minimizes competition between species. However, species who live in similar areas typically compete with each other. The Lotka–Volterra equation states that two competing species can coexist when intra-specific (within species) competition

6771-463: The estimation of the competition coefficients. This postulate, however, can be misguided, as it ignores the impacts that the resources of each category have on the organism and the impacts that the organism has on the resources of each category. For instance, the resource in the overlap region can be non-limiting, in which case there is no competition for this resource despite niche overlap. An organism free of interference from other species could use

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6882-440: The evolution of resistance to herbicides . Rapid life cycles, large populations, and ability to spread large numbers of seeds long distances also allow weed species with these general characteristics to evolve quickly. The concept of weeds also overlaps with the concept of invasive species , both in the sense that human activities tend to introduce weeds outside their native range, and that an introduced species may be considered

6993-587: The existence of both ecological equivalents and empty niches. An ecological equivalent to an organism is an organism from a different taxonomic group exhibiting similar adaptations in a similar habitat, an example being the different succulents found in American and African deserts, cactus and euphorbia , respectively. As another example, the anole lizards of the Greater Antilles are a rare example of convergent evolution , adaptive radiation , and

7104-482: The existence of ecological equivalents: the anole lizards evolved in similar microhabitats independently of each other and resulted in the same ecomorphs across all four islands. In 1927 Charles Sutherland Elton , a British ecologist , defined a niche as follows: "The 'niche' of an animal means its place in the biotic environment, its relations to food and enemies ." Elton classified niches according to foraging activities ("food habits"): For instance there

7215-466: The existing plant and soil community has been disrupted or damaged in some way. Adaptation to disturbance can give weeds advantages over desirable crops, pastures, or ornamental plants. The nature of the habitat and its disturbances will affect or even determine which types of weed communities become dominant. In weed ecology some authorities speak of the relationship between "the three Ps": plant, place, perception. These have been very variously defined, but

7326-472: The exotic or invasive species . The mathematical representation of a species' fundamental niche in ecological space, and its subsequent projection back into geographic space, is the domain of niche modelling . Contemporary niche theory (also called "classic niche theory" in some contexts) is a framework that was originally designed to reconcile different definitions of niches (see Grinnellian, Eltonian, and Hutchinsonian definitions above), and to help explain

7437-799: The expense of less "weedy" species. For example, kudzu , the infamous invasive vine found throughout the Southeastern United States, is expected to spread northward due to climate change. Increased competitive strength of agricultural weeds in future climate conditions threaten future ability to grow crops. Existing weed management practices will likely fail under future changes in climate conditions, meaning new agricultural techniques will be needed for global food security. Suggested techniques are holistic, transitioning away from reliance on herbicide, and include aggressive adaptation of agroforestry and use of allelopathic crop residues to suppress weeds. Ecological niche In ecology ,

7548-427: The extinction of the tarpan has been filled by other animals (in particular a small horse breed, the konik ). Also, when plants and animals are introduced into a new environment, they have the potential to occupy or invade the niche or niches of native organisms, often outcompeting the indigenous species. Introduction of non-indigenous species to non-native habitats by humans often results in biological pollution by

7659-577: The extreme or barren conditions present make it more favourable to reproduce asexually in order to increase reproductive success rather than invest energy into sexual reproduction . Pioneer species will eventually die, create plant litter , and break down as " leaf mold " after some time, making new soil for secondary succession (see below), and releasing nutrients for small fish and aquatic plants in adjacent bodies of water. Some examples of pioneering plant species: The pioneering fauna will colonize an area only after flora and fungi have inhabited

7770-434: The figure, where it is clear that for the narrower distributions (top) there is no competition for prey between the extreme left and extreme right species, while for the broader distribution (bottom), niche overlap indicates competition can occur between all species. The resource-utilization approach postulates that not only can competition occur, but that it does occur, and that overlap in resource utilization directly enables

7881-442: The first of life forms, and break down the rocks into soil for plants. Since some uninhabited land may have thin, poor quality soils with few nutrients, pioneer species are often hardy plants with adaptations such as long roots, root nodes containing nitrogen-fixing bacteria , and leaves that employ transpiration . Note that they are often photosynthetic plants, as no other source of energy (such as other species) except light energy

7992-407: The first place, and may have not been considered nuisances at the time, but rather beneficial. Weed control encompasses a range of methods used by humans to stop, reduce or prevent the growth and reproduction of weeds within agricultural or other managed environments. Some weed control is preventative, implementing protocols to stop weeds from invading new areas. Cultural weed control involves shaping

8103-433: The full range of conditions (biotic and abiotic) and resources in which it could survive and reproduce which is called its fundamental niche . However, as a result of pressure from, and interactions with, other organisms (i.e. inter-specific competition) species are usually forced to occupy a niche that is narrower than this, and to which they are mostly highly adapted ; this is termed the realized niche . Hutchinson used

8214-453: The habit of weeds is important for non-chemical methods of weed control, such as plowing, surface scuffling, promotion of more beneficial cover crops, and prevention of seed accumulation in fields. For example, amaranth is an edible plant that is considered a weed by mainstream modern agriculture. It produces copious seeds (up to 1 million per plant) that last many years, and is an early-emergent fast grower. Those seeking to control amaranth quote

8325-401: The idea of competition for resources as the primary mechanism driving ecology, but overemphasis upon this focus has proved to be a handicap for the niche concept. In particular, overemphasis upon a species' dependence upon resources has led to too little emphasis upon the effects of organisms on their environment, for instance, colonization and invasions. The term "adaptive zone" was coined by

8436-457: The idea that the niche of a species is determined by the habitat in which it lives and its accompanying behavioral adaptations . In other words, the niche is the sum of the habitat requirements and behaviors that allow a species to persist and produce offspring. For example, the behavior of the California thrasher is consistent with the chaparral habitat it lives in—it breeds and feeds in

8547-493: The last nineteenth century in American cities. Urban expansion and development created ideal habitats for weeds in nineteenth-century America. Reformers consequently saw weeds as a part of the larger problem of filth, disease, and moral corruption that plagued the urban environments, and weeds were seen as refuge for "tramps" and other criminal or undesirable people. The St. Louis Post-Dispatch credited weeds as causing diphtheria , scarlet fever , and typhoid . In St. Louis between

8658-796: The managed environment to make it less favorable for weeds. Once weeds are present in an area, a wide variety of means to destroy the weeds and their seeds can be employed. Since weeds are highly adaptable, relying on a single method to control weeds soon results in the invasion or adaptation of weeds that are not susceptible. Integrated pest management as it applies to weeds refers to a plan of controlling weeds that integrates multiple methods of weed control and prevention. Methods of preventative weed control include cleaning equipment, stopping existing weeds in nearby areas from producing seed, and avoiding seed or manure that could be contaminated with weeds. A wide variety of cultural weed control methods are used, including cover cropping , crop rotation , selecting

8769-486: The mantra "This year’s seeds become next year’s weeds!". However, another view of amaranth values the plant as a resilient food source. Some people have appreciated weeds for their tenacity, their wildness and even the work and connection to nature they provide. As Christopher Lloyd wrote in The Well-Tempered Garden : Many gardeners will agree that hand-weeding is not the terrible drudgery that it

8880-542: The meaning of niche as a recess in a wall for a statue, which itself is probably derived from the Middle French word nicher , meaning to nest . The term was coined by the naturalist Roswell Hill Johnson but Joseph Grinnell was probably the first to use it in a research program in 1917, in his paper "The niche relationships of the California Thrasher". The Grinnellian niche concept embodies

8991-576: The most competitive cultivars of crops, mulching, planting with optimal density, and intercropping . Mechanical methods of weed control involve physically cutting, uprooting, or otherwise destroying weeds. On small farms, hand weeding is the dominant means of weed control, but as larger farms dominate agriculture, this method becomes less feasible. On many operations, however, some hand-weeding may be an unavoidable component of weed control. Tillage , mowing , and burning are common examples of mechanical weed control on larger scales. New technology increases

9102-475: The narrow extent of focus, data sets characterizing Eltonian niches typically are in the form of detailed field studies of specific individual phenomena, as the dynamics of this class of niche are difficult to measure at a broad geographic scale. However, the Eltonian niche may be useful in the explanation of a species' endurance of global change. Because adjustments in biotic interactions inevitably change abiotic factors, Eltonian niches can be useful in describing

9213-444: The other closely related species within the same broad taxonomic class, but there are exceptions. A premier example of a non-standard niche filling species is the flightless, ground-dwelling kiwi bird of New Zealand, which feeds on worms and other ground creatures, and lives its life in a mammal-like niche. Island biogeography can help explain island species and associated unfilled niches. The ecological meaning of niche comes from

9324-402: 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

9435-561: The overall response of a species to new environments. The Hutchinsonian niche is an " n-dimensional hypervolume", where the dimensions are environmental conditions and resources , that define the requirements of an individual or a species to practice its way of life, more particularly, for its population to persist. The "hypervolume" defines the multi-dimensional space of resources (e.g., light, nutrients, structure, etc.) available to (and specifically used by) organisms, and "all species other than those under consideration are regarded as part of

9546-441: The paleontologist George Gaylord Simpson to explain how a population could jump from one niche to another that suited it, jump to an 'adaptive zone', made available by virtue of some modification, or possibly a change in the food chain , that made the adaptive zone available to it without a discontinuity in its way of life because the group was 'pre-adapted' to the new ecological opportunity. Hutchinson's "niche" (a description of

9657-410: The past, several species inhabited an area, and all of these species had overlapping fundamental niches. However, through competitive exclusion, the less competitive species were eliminated, leaving only the species that were able to coexist (i.e. the most competitive species whose realized niches did not overlap). Again, this process does not include any evolutionary change of individual species, but it

9768-533: The planet." — Paleontologist David Jablonsky An alternate definition often used by biologists is any species, not just plants, that can quickly adapt to any environment. Some traits of weedy species are the ability to reproduce quickly, disperse widely, live in a variety of habitats, establish a population in strange places, succeed in disturbed ecosystems and resist eradication once established. Such species often do well in human-dominated environments as other species are not able to adapt. Common examples include

9879-430: The potential to adapt their morphology, growth, and appearance in response to their conditions. The potential within a single individual to adapt to a wide variety of conditions is sometimes referred to as an "all-purpose genotype." Disturbance-adapted plants typically grow rapidly and reproduce quickly, with some annual weeds having multiple generations in a single growing season. They commonly have seeds that persist in

9990-454: The presence of niche differentiation (through competition) will be relatively easy. Importantly, there is no evolutionary change of the individual species in this case; rather this is an ecological effect of species Y out-competing species X within the bounds of species Y's fundamental niche. Another way by which niche differentiation can arise is via the previous elimination of species without realized niches. This asserts that at some point in

10101-439: The process of secondary succession . Disturbances may include floods, tornadoes , forest fires , deforestation , or clearing by other means. Pioneer species tend to be fast-growing, shade-intolerant, and tend to reproduce large numbers of offspring quickly. The seeds of pioneer species can sometimes remain viable for years or decades in the soil seed bank and often are triggered to sprout by disturbance. Mycorrhizal fungi have

10212-433: The range of mechanical weed control options. One newly emerging form of mechanical weed control uses electricity to kill weeds. Mechanical weed control has been increasingly replaced by the use of herbicides . The reliance on herbicides has resulted in the rapid evolution of herbicide resistance in weeds, making previously effective herbicide treatments useless for the control of weeds. In particular, glyphosate , which

10323-565: The river where the beaver lives. Thus, the beaver affects the biotic and abiotic conditions of other species that live in and near the watershed. In a more subtle case, competitors that consume resources at different rates can lead to cycles in resource density that differ between species. Not only do species grow differently with respect to resource density, but their own population growth can affect resource density over time . Eltonian niches focus on biotic interactions and consumer–resource dynamics (biotic variables) on local scales. Because of

10434-658: The root meristem in that direction, if the interaction is kin. Simonsen discusses how plants accomplish root communication with the addition of beneficial rhizobia and fungal networks and the potential for different genotypes of the kin plants, such as the legume M. Lupulina, and specific strains of nitrogen fixing bacteria and rhizomes can alter relationships between kin and non-kin competition. This means there could be specific subsets of genotypes in kin plants that selects well with specific strains that could outcompete other kin. What might seem like an instance in kin competition could just be different genotypes of organisms at play in

10545-403: The root secretions, also called exudates, plants can make this determination. The communication between plants starts with the secretions from plant roots into the rhizosphere. If another plant that is kin is entering this area the plant will take up exudates. The exudate, being several different compounds, will enter the plants root cell and attach to a receptor for that chemical halting growth of

10656-425: The same plants might be hardy pioneers, cosmopolitan species, volunteers, "spontaneous urban vegetation," etc. Although whether a plant is a weed depends on context, plants commonly defined as weeds broadly share biological characteristics that allow them to thrive in disturbed environments and to be particularly difficult to destroy or eradicate. In particular, weeds are adapted to thrive under human management in

10767-484: The same resources if each species is limited by different resources, or differently able to capture resources. Different types of phytoplankton can coexist when different species are differently limited by nitrogen, phosphorus, silicon, and light. In the Galapagos Islands , finches with small beaks are more able to consume small seeds, and finches with large beaks are more able to consume large seeds. If

10878-534: The same way as intentionally grown plants. Since the origins of agriculture on Earth, agricultural weeds have co-evolved with human crops and agricultural systems, and some have been domesticated into crops themselves after their fitness in agricultural settings became apparent. More broadly, the term "weed" is occasionally applied pejoratively to species outside the plant kingdom, species that can survive in diverse environments and reproduce quickly; in this sense it has even been applied to humans . Weed control

10989-472: The same ways as the incoming species, however examples of this are also numerous. In ecology , niche differentiation (also known as niche segregation , niche separation and niche partitioning ) 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 (ecological roles) compete , then one will inevitably drive

11100-619: The sixteenth century, the concept of a "weed" was better defined as a "noxious" or undesirable type of plant, as referenced metaphorically in William Shakespeare 's works. An example of a Shakespearean reference to weeds is found in Sonnet 69 : To thy fair flower add the rank smell of weeds: / But why thy odour matcheth not thy show, / The soil is this, that thou dost common grow. In London during this period, poor women were paid low wages to weed gardens and courtyards. After

11211-401: The soil directly. The dandelion is also one of several species which break up hardpan in overly-cultivated fields, helping crops grow deeper root systems. Some garden flowers originated as weeds in cultivated fields and have been selectively bred for their garden-worthy flowers or foliage. An example of a crop weed that is grown in gardens is the corncockle , ( Agrostemma githago ), which was

11322-457: The soil that increase the symbiotic efficiency. Predator partitioning occurs when species are attacked differently by different predators (or natural enemies more generally). For example, trees could differentiate their niche if they are consumed by different species of specialist herbivores , such as herbivorous insects. If a species density declines, so too will the density of its natural enemies, giving it an advantage. Thus, if each species

11433-444: The species, environmental variation..., and interactions between the two—in particular the abilities of some species, especially our own, to modify their environments and alter the range dynamics of many other species." Alteration of an ecological niche by its inhabitants is the topic of niche construction . The majority of species exist in a standard ecological niche, sharing behaviors, adaptations, and functional traits similar to

11544-809: The two species interact, how they use their resources, and the type of ecosystem in which they exist, among other factors. In addition, several mathematical models exist to quantify niche breadth, competition, and coexistence (Bastolla et al. 2005). However, regardless of methods used, niches and competition can be distinctly difficult to measure quantitatively, and this makes detection and demonstration of niche differentiation difficult and complex. Over time, two competing species can either coexist, through niche differentiation or other means, or compete until one species becomes locally extinct . Several theories exist for how niche differentiation arises or evolves given these two possible outcomes. Niche differentiation can arise from current competition. For instance, species X has

11655-639: The underbrush and escapes from its predators by shuffling from underbrush to underbrush. Its 'niche' is defined by the felicitous complementing of the thrasher's behavior and physical traits (camouflaging color, short wings, strong legs) with this habitat. Grinnellian niches can be defined by non-interactive (abiotic) variables and environmental conditions on broad scales. Variables of interest in this niche class include average temperature, precipitation, solar radiation, and terrain aspect which have become increasingly accessible across spatial scales. Most literature has focused on Grinnellian niche constructs, often from

11766-442: The underlying processes that affect Lotka-Volterra relationships within an ecosystem. The framework centers around "consumer-resource models" which largely split a given ecosystem into resources (e.g. sunlight or available water in soil) and consumers (e.g. any living thing, including plants and animals), and attempts to define the scope of possible relationships that could exist between the two groups. In contemporary niche theory,

11877-1148: The weed traits listed by H.G. Baker are widely cited. Examples of such ruderal or pioneer species include plants that are adapted to naturally-occurring disturbed environments such as dunes and other windswept areas with shifting soils, alluvial flood plains, river banks and deltas , and areas that are burned repeatedly. Since human agricultural and horticultural practices often mimic these natural disturbances that weedy species have adapted for, some weeds are effectively preadapted to grow and proliferate in human-disturbed areas such as agricultural fields, lawns, gardens, roadsides, and construction sites. As agricultural practices continue and develop, weeds evolve further, with humans exerting evolutionary pressure upon weeds through manipulating their habitat and attempting to control weed populations. Due to their ability to survive and thrive in conditions challenging or hostile to other plants, weeds have been considered extremophiles . Due to their evolutionary heritage as disturbance-adapted pioneers, most weeds exhibit incredibly high phenotype plasticity, meaning that individual plants hold

11988-444: The years of 1905-1910, weeds became viewed as a major public health hazard, believed to cause typhoid and malaria, and legal precedents were set in order to control weeds that would help facilitate the adoption of weed control laws throughout the country. "Weed" as a category of plant overlaps with the closely related concepts of ruderal and pioneer species . Pioneer species are specifically adapted to disturbed environments, where

12099-544: Was accidentally introduced. The Klamathweed Beetle , a species that specializes in consuming the plant, was imported during World War II. Within several years Klamath weed was reduced to a rare roadside weed. In locations where predation and mutually competitive relationships are absent, weeds have increased resources available for growth and reproduction. The weediness of some species that are introduced into new environments may be caused by their production of allelopathic chemicals which indigenous plants are not yet adapted to,

12210-415: Was once considered a revolutionary breakthrough in weed control, was relied upon heavily when it was first introduced to agriculture, resulting in rapid emergence of resistance. As of 2023, 58 weed species have developed resistance to glyphosate. Herbicide resistance in weeds has rapidly developed into new, increasingly challenging forms as the plants continually evolve. Non-target site resistance, or NTSR,

12321-467: Was probably an incidental effect of plowing. Ancient Egyptians, Assyrians, and Sumerians had no specific word for "weeds," seeing all plants as having some use. The English word "weed" can be traced back to the Old English weod , which refers to woad , rather than a category of plant as in the modern usage; in early medieval European herbals, each plant is regarded as having its own "virtues". By

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