(From Community Ecology lecture L8)

History

1917 Grinnell - "habitat or environment a species can occupy"
1927 Elton - "Function fulfilled by a species within its ecological community"
1957 (Hutchinson's definition) - "n-dimensional hypervolume" defining the requirements of a population to persist"

• Usually represented in 2 dimensions

Fundamental Niche:

• Part of environment that a species could occupy in the absense of interactions with other species

Realized Niche:

• Result of pressureand interactions with other species such as competition or exploitation

Neutral Theory

• The null hypothesis to niche theory
  • Stresses inter-specific interactions
• If all species within a trophic level all had the same probability per capita of reproducing, dying, dispersing and speciating, we can model a "null hypothesis" and compare with observed values to see if there is a pattern
• Each individual has a $1/(J-1)$ probability of colonizing the unfilled site where $J$ is the total number of sites
• Each species has a $N_i/(J-1)$ probability of colonizing the unfilled site where $N_i$ is the number of species $i$.