Concept of ecological niche

CONCEPT OF ECOLOGICAL NICHE

Griennel proposes ecological niche term.  He proposed the term for reducing the competition in the ecosystem.  Actually, each organism has limited range of space and diet selection and this range is determined by so many factors. So, the limited favorable area where species can enjoy the different factors is known as Ecological Niche.  Basically, niche is related with Micro-habitat.  According to Griennel, species is the distributional unit in which it is held by structural and instinctive limitations and no any two species can occupy the same space.  The meaning of niche is a place, employment or best-fit activity of organism.  So, the nicheis differentiated from habitat.  It is based on the physical and functional role of the organism.  So on the basis of habitat and trophic level niche can be differentiated.

Types of Niche

Habitat Niche

It is also known as Spatial Niche.  When any organism is showing the fixed territory or living space, then it is known as Habitat or Spatial Niche.  It shows the differentiation in microhabitat.  It means the habitat of many species may be similar, but the micro-habitat of organisms differs, which reduces the competition in the organisms.  It is supported by so many examples.  O'Neill reports one interesting case.

He studied the seven species growing at the same habitat and all species having the same trophic level.  But it is observed that all seven species show different microhabitats, and it produces many gradients in the decomposition stage.  These species and microhabitats are following :

            1.         Euryurus erythropygus:  Dominants in heartwood of logs.

            2.         Pseudopalydesmus serratus: Superficial wood of log.

            3.         Narcueus amerelcanus: Outer surface of logs but below the bark.

            4.         Seutotus aranulatus: Under log but on log surface.

            5.         Fontaria Virginians: Under log but on ground surface.

            6.         Cleidognia species: Within litter leaves.

          7.        Abacion: Below litter on ground surface.

Similar examples were studied by Sharma and Dwivedi.  They studied that the microhabitat of fungal species indicate the same habitat, but the microhabitat differs like Myrothecium roridum present at upper inflorescence axis, while Myrothecium stratisporum the middle internodes, and Stagnospora Graminella present at lower internodes.

Trophic Niche

The niche, which is based on the functional behaviour of the organisms in the ecosystem, is known as Trophic position of the organism in the ecosystem.  Many examples are given in the favor of Trophic niche.  The Galapagos is land of the South America, the nature of three bird species is studied.  These birds indicate similar habitat and microhabitat.  But the food trophic position is different.

            a.         Geospiza:  It searches the food from ground surface.

            b.         Camarhynchus:  It searches the food from upper surface of tree.

                        c.         Certhidia:  It is insect eaten.  Similarly, in another example it is indicated that two birds are living in the same nest, it means the microhabitat is similar, but these indicate major differences in the trophic level, like ploceous melanoephalur is the insect eater bird, it means it is carnivorus while ploceus collasis is seedeater bird.  It means it is herbivores in nature.  One interesting point is studied in aquatic ecosystem, where two aquatic bugs is living together in the same habitat.  These are Notonacta and Corixa.  But, Notonacta is predator, while Corixa is detritivore.

Multifactor Niche

If the organisms is affected by two or more than two factors at a time, then it is known as Multifactor Niche.  Hutchinnson gives this idea.  According to him, at a time, many pressures are applied on organism, which determine the various range of organism's movement.  Generally, the space of organism movement is limited in the ecosystem, which is known as Niche space.  If any organism is controlled by two factors at a time, then it is known as area Niche.  If Area Niche of two organisms is independent, then it shows the organisms is independent, and then it shows the Non-competitive environment.  Similarly, if organism is controlled by three factors, then this niche is known as 3-D Niche or Hyper-volume niche.  Hutchison proposes this term.  If the niche of two organisms is completely separated, then it will be Non-competitive niche.  But, if any part of Niche overlap with each other, then it is known as Overlapping Niche.  It shows increasing competition in the environment.  If we take the 4th factors, then it is known as fundamental niche.  With the help or study of fundamental Niche, we can find out the degree of competition in the ecosystem.  As the overlapping increases, the competition parallel increases.  The complete overlapping of organism is going on, then the species fight with each other, and in this competition, one species is destroyed and only one species survive.  It favours the "Survival of the fittest" concept proposed by Darwin.