Transcript Slide 1

Community structure
Physical structure
Dispersal-driven structure
Predation-driven structure
Competition-driven structure
Physical structure
• Physical template
• Biological template
– Paradox of the plankton
– Dominant species
• Trees
• Corals
• Surfaces
– Ecological engineers
• impoundments
• cavities
• mounds
Habitat template
Whittaker’s analysis of the Smoky Mountains
Dominant species
provide structure
Ecological engineers
• Dams
• Holes
• Mounds
Dispersal-based structure
• Supply-side ecology
•
Propagule pressure
•
Predictability
• Carousel mode
• Temporal mass effects
Scoured Island
River Bedrock Scour Bar
River Floodplain
Carousel model
Temporal mass effect
The tingle tree in
SW Australia has
not reproduced in
over 1000 years.
Seed banks as a form of temporal mass effect
Dispersal-based structure
• Supply-side ecology
•
Propagule pressure
•
Predictability
• Carousel model
• Temporal mass effects
Competition-based structure
• Niche differentiation
•
In space
•
In time
• Assembly rules
•
Diamond’s birds
•
Brown’s mice
•
Lawlor’s and Wilson’s null models
• Ghost of competition past
Niche theory
• Grinnell 1917. The ultimate distributional
unit. Physical and climatic limits
• Elton 1927. Fundamental role of a species.
It’s occupation, or how it makes its living.
• Hutchinson 1958. N-dimensional hypervolume.
• Hutchinson. Fundamental & Realized Niche
• Whittaker, Levin & Root. 1973. Niche,
habitat & ecotope
Consider the concept of niche,
if I knew what it meant I'd be rich
Its dimensions are n,
and a knowledge of Zen
is essential to fathom the bitch
Cottam and Parkhurst
And NUH is the letter I use to spell Nutches
Who live in small caves, known as Nitches, for hutches.
These Nutches have troubles, the biggest of which is
The fact that there are many more nutches than niches.
Each nutch in a Nitch knows that some other Nutch
Would like to move into his nitch very much.
So each Nutch in a nitch has to watch that small Nitch
Or Nutches who haven't got nitches will snitch.
Dr. Zuess
On beyond zebra
Niche structure as a
consequence of
competitive displacement
Brown 1975
Diamond 1975
Null models – Reorganization algorithms
RA1: species number and resource
categories retained. Randomly assign
values for proportion of diet (between 0 &
1 such that for a species values sum to 1).
Since 0 is rare, niche breadth was too
high
RA2: Retained 0s, and randomly assigned
other values (perhaps should have
randomly assigned 0s?).
• RA3: Retained not only the original degree
of specialization, but also the original
consumer nichne breadths – randomly
reassigned all values including 0s.
• RA4: Reassigned only the non-0 values
Competition-based structure
• Niche differentiation
•
In space
•
In time
• Assembly rules
•
Diamond’s birds
•
Brown’s mice
•
Lawlor’s and Wilson’s null models
• Ghost of competition past
Predation-based structure
• Food web structure
•
Complexity and stability
•
Representation
• Keystone species
•
Factors influencing food web stability
• Top-down/bottom up control
•
Fertilizations and cages
•
Are food webs all wet?
Multiple steady states