12/1/2009
Defining the niche
Ecological Niches
A funny thing is the niche
If I knew what it was I'd be rich.
It's dimensions are n
And a knowledge of zen
Are needed to fathom the bitch.
Defining the Niche
• Joseph Grinnell (1877-1939)
• American born, Berkeley professor
• Niche is a subdivision of habitat
Defining niche
• Charles Elton (1900-1991)
– British, Oxford ecologist
– Animal Ecology, Journal of Animal
Ecology
– 1933 “in the sense that we speak
of trades or jobs or profession in a
human community”
Defining the niche
• G. Evelyn Hutchinson (1903-1991)
• British, Yale ecologist
• The Ecological Theater and the Evolutionary
Play (1965)
• 1957
• n-dimensional hypervolume
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Defining Niche
• Doesn’t exist without the organism
• A niche is not a place but an idea
– Ecology: Begon, Townsend and Harper
• Adaptation: redefining the niche
The Niche
• Still debatable
• Where, what, how an organism lives
– Where = habitat
– What = tolerances (physiological)
– How= what it does
• What it does and where it is that gives it the
highest fitness
Fundamental and Realized Niche
• G. Evelyn Hutchinson
• Organisms may not be found where it could
possibly be found
– Predators and competitors reduce the
fundamental niche to the realized niche
– Fundamental niche: constrained by physiology
– Realized niche = fundamental plus biological
influences
Niche Conservation
• Chalkboard
– Show fundamental vs. realized
• Phylogenetically close organisms tend to have
similar niches
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Niches
• Can niches be shared?
– Theoretically, not in a stable environment
– Competitive exclusion principle
– Niche differentiation
Niche Breadth
R. Levins 1968
B
1
p
2
i
Niche overlap: Pianka
O jk
Show 1 D then 2 D then 2D with
fitness
Show 2D with overlap
pij pik
pij2 pik2
• measure of overlap between species j and species k
•pij is the proportion that resource i is of the total resources used by
species j, and
•pik is the proportion that resource i is of the total resources used by
species k.
•This measure ranges from 0 (no resources used in common) to 1
(complete overlap).
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Canonical correspondence analysis
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