Niche

"The functional role & position of an organism in its community." ~ Joseph Grinnell(1917, 1924, 1928).

To determine the niche of a species must know,

  • Where it lives (habitat niche)
  • Types of foods that it feeds on (feeding or trophic niche)
  • How and when it reproduces (reproductive niche)
  • Physical and chemical factors (physical and chemical niche)

Niche Properties

  1. Niche overlap
  2. Niche breadth
These characteristics are seen only when two or more species share the same resources.

Niche overlap and competition 


When resources are shared among species it results in niche overlap between competing species.
Niche overlap may occur in different ways,
  1. Complete overlap
  2. Partial overlap
  3. Non-overlap
Complete overlap - 
  • Species have identical fundamental niches.
Complete overlap


Partial overlap - 
  • Fundamental niches may overlap only partially, with some niche space being shared.
Partial overlap (Equal overlap)


Partial overlap (Unequal overlap)




non-overlap - 
  • Fundamental niches might abut against one another, no direct competition can occur between species 
  • A niche relationship may reflect the avoidance of competition.
Non-overlap (Abutting)


Non-overlap (Disjunct)


Niche Breadth


It is also referred to as "niche width" or "niche size".

Eg. The Housefly (Musca domestic) can tolerate the dimensions of temperature ranging from 5℃ to 45 ℃.
This overall range of temperature that the housefly tolerates is called niche breadth.

The niche breadth is usually described as narrow or broad. (narrow ranges of tolerance or broad ranges of tolerance)

  • Highly specialized organisms have narrow tolerance limits along with one or more of their niche dimensions. They are called Specialists species. They have very specific habitat requirements They are often relatively rare.
Specialists species



  • Organisms with broad tolerance are more generalized with more flexible habitat requirements and common. They are called Generalist species. They are more abundant.


Generalist species


Niche breadth provides an indication of resource utilization of species and its not fixed value. It may change give arise, 

  • Niche changes
  • niche shifts