•An ecological niche is the role that a speciesplays and its position within the environment in which it develops; it is the way in which it manages to satisfy its food and shelter needs, how it survives and how it reproduces.
•A species’ niche includes all its interactions with both bioticand abiotic factors in its environment.
•Let us remember that biotic factors are all living beings, while abiotic factors are all those things that have no life.
Characteristics
•Some of the main characteristics that we can observe in an ecological niche are:
•All living beings that inhabit the earth play a role in their environment.
•It depends on the function and place of a living being in the environment.
•Animals in the ecological niche have different and unique functions.
•If there are two species playing the same role, an interspecific competition will be created.
•The correct description of a niche can include descriptions of life, habitat and the place of the organism in the food chain.
•It includes how to feed, compete, hunt and defend.
•It is closely related to habitat.
•The niche of a species is basically an ecological function or a set of conditions, resources and interactions it needs to survive.
•The dictionary meaning of the term “niche” is a place but it should not be confused with habitat (which also means a place to live). The term “ecological niche” refers not only to the physical place occupied by an organism, but also its functional role in the community.
•Thus, ecological niche of any organism concerns not only space where it lives but also what it does?
•What organisms does it feed?
•To what organisms it serves as food?
•What kind of minerals does it require from the environment?
•How does it respond and how it modifies its physical and biotic environment?
•In simple. words, an organism‘s habitat may be spoken of as its ADDRESS while ecological niche as its PROFESSION.
•Thus ecological niche is a particular combination of physical factors and biotic relations required by a species for its life activities and continued existence in the society.
•Ecological niche means to determine the organism status in the natural community i.e. it is concerned with to know the mode of its nutrition, the energy source, rate of metabolism and growth, effect of organism on other species and the manner in which it modifies the surrounding environment.
Importance
•Ecological niches are important for a given place because they allow different species to live together, usually without competition.
•Each species knows its position in both the ecosystem and the food chain.
•The number of niches in an ecosystem determines the number of species in it, that is, they define the diversity of the place.
•Following ,examples will clearly illustrate the difference between habita.tand ecological niche.
•Example 1: Two aquatic bugs Notonectid (back-swimmer) and Corixa (water bug) live in same habitat i.e. both are found gliding over the surface of water in a freshwater pond, but they occupy different trophic niches.
•Notonectid is an active predator that grasp and eat small animals, whereas Corixa feeds largely on decaying vegetation.
•Thus, one species is carnivore and serves as consumer, the other one is saprophytic and serves as decomposer.
•Both organisms have the same address (i.e. both live on the surface of water) but their biological profession or the so-called ecological niche is different.
Types of Ecological niche
•Grinnell Ian niche
•The Grinnell Ian niche concept embodies 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 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.
•This perspective of niche allows for 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 the existence of ecological equivalents: the anole lizards evolved in similar microhabitats independently of each other and resulted in the same ectomorphs across all four islands.
Eltonian niche
•Elton classified niches according to foraging activities (“food habits”):
•For instance, there 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, 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 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.
Hutchinsonian niche
•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 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 a given species), ‘niche partitioning’ (resource differentiation by coexisting species), and ‘niche overlap’ (overlap of resource use by different species).
•An organism free of interference from other species could use 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.
•The term “adaptive zone” was coined by 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 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 a niche specific to each species.
•For example, Australian grasslands species, though different from those of the Great Plains grasslands, exhibit similar modes of life.