Ecological Niche – Concept of Niche

Introduction:

Habitat and Niche – Concept of Niche

The position of a species within an ecosystem can be termed an ecological niche. It describes both the spectrum of circumstances required for the species’ survival and its ecological significance in the ecosystem. It includes all of the interactions between a species and the biotic and abiotic environment and, thus, represents a very basic and fundamental ecological concept.

Aspects of Ecological Niche

This indicates that the concept of niche has two sides that are not so tightly related. However, both are either implicitly or explicitly mixed. One concerns the effects that the environment has on a species, and the other concerns the effects that a species has on the environment.

Ecology is all about interactions between organisms, and since a species’ persistence is determined by the existence of other species, all species are naturally both impacted by the environment and affect the environment for other species. Both these aspects of the ecological niche are a part of ecological space. An ecological space is defined by all combinations of biotic and abiotic environmental conditions. This is a place where the species population can persist and thus utilize resources and impact its environment.

Niche Vs Habitat

In ecology, habitat and niche are two distinct concepts. The above definition of habitat relates to the particular environment in which an organism lives. However, ecologists use a more sophisticated phrase when referring to animals interacting in an ecosystem, which is niche.

A niche is a way or function that organisms fit into their particular habitats in ecological terms. Ecologists have arrived at the conclusion that two species cannot fulfill the same role in the same niche at the same time. This is frequently due to resource rivalry. Sometimes, but not usually, this condition results in extinction. Two competing species may eventually develop minor changes and hence new niches throughout time.

Niche Formation

Biotic and abiotic factors of an ecosystem are helpful in shaping the niche of an ecosystem. Natural selection is helpful in selecting which niche can survive or which cannot. Species adapt themselves to survive in an ecosystem. Several factors of the population, such as competition, parasitism, and predation, affect the niche. Niches present in the ecosystem evolve as these factors change.

Approaches To The Ecological Niche

However, it is useful to distinguish three main approaches to the niche. Environmental conditions are necessary for a species’ presence and maintenance of its population; this is emphasized by the first approach.

The functional role of species within ecosystems is stressed by the second approach. The third approach emphasizes the dynamic position of species within a local community, shaped by species’ biotic and abiotic requirements and by coexistence with other species.

Taxonomic Diversity Versus Functional Diversity

• The resources it requires and its role or function in the environment define an ecological niche for a species.
• When the concept of the niche was introduced, it focused on the habitat requirements of a species for it to survive and reproduce.
• Later, its definition was expanded by disaggregating the habitat into the multiple resources it embodied.

• The physical space a species inhabits, the temperature and moisture conditions of the space, seasonality in abiotic and biotic variables that the space experiences, as well as food needs and interactions with other species, are all taken into account.
• The ecological niche was also defined in terms of the role of a species in the environment.
• Along with all this, an analysis of the resource requirements for several species from different taxa, revealing that the principal niche axes are food, habitat use, and time was also presented.

Ecological Niche In Aquatic Ecosystems

All types of ecosystems have ecological niches. There is no conceptual distinction between aquatic and terrestrial niches.

For the ecological niche of aquatic organisms, the most important dimensions include temperature, dissolved oxygen, habitat structure, predation, and plant nutrients. A much narrower range of temperature is there for aquatic ecosystems than the range for terrestrial ecosystems because liquid water has a minimum temperature of 0°C.

For phytoplankton and zooplankton, the thermal thresholds are weak, as shown by the distribution of species across wide ranges of latitude and elevation. The thresholds are more important for large invertebrates and especially for fish.

We can take an example of the family Salmonidae, which contains many species that are intolerant of waters exceeding 15–20°C. Montane or subarctic lakes, which are perennial cool water lakes, cannot sustain populations of many kinds of warm water fishes, such as most species of the sunfish family. Only approximately 10 mg/L of oxygen is held at low temperatures and 6–7 mg/L at high temperatures. That is how respiration can make water anoxic if it is not offset by photosynthetically produced oxygen or by contact of water with the atmosphere. The water that is in contact with sediment, for example, can remove all oxygen from water in a matter of a few days due to higher rates of respiration.

Some of the environments which are aquatic are much more subject to oxygen depletion than others. High-gradient mountain streams with low amounts of respiration are on one end of the spectrum in that they have very little potential for oxygen depletion. However, there is much respiration and less efficient gas exchange with the atmosphere, showing a much higher probability of oxygen depletion.

The organisms’ distribution reflects in their ability to tolerate oxygen depletion. For example, some fishes show a wide range of tolerance to oxygen depletion. Those fishes are on one extreme that can obtain oxygen from the atmosphere and some fishes have a small, upturned mouth capable of drawing oxygen from the top 1–2 mm of water in contact with the atmosphere. Those fishes which are intermediate in tolerance have no special means of obtaining oxygen but have high physiological resistance to oxygen depletion.  In contrast, other fishes are moderately or highly sensitive to oxygen depletion.