SLIDE 1
Food webs - The Who eats Who in Ecology. Nodes: Species Links: - - PowerPoint PPT Presentation
Food webs - The Who eats Who in Ecology. Nodes: Species Links: - - PowerPoint PPT Presentation
Food webs - The Who eats Who in Ecology. Nodes: Species Links: predator-prey interactions Food webs - The Who eats Who in Ecology. Directed biomass flows from prey to predator Strong links: High biomass flow Weak links: Low biomass flow
SLIDE 2
SLIDE 3
Food webs - The Who eats Who in Ecology. Directed biomass flows from prey to predator Strong links: High biomass flow Weak links: Low biomass flow
SLIDE 4
Food webs - The Who eats Who in Ecology. Top predators Intermediate consumers Primary producers Trophic gradient
SLIDE 5
Complexity or stability?!
Large and complex systems are in general unlikely to be stable! * Large and complex systems are in general unlikely to be stable! *
* May R. Will a large complex system be stable? Nature 238 1972
SLIDE 6
Complexity or stability?!
Large and complex systems are in general unlikely to be stable! * Large and complex systems are in general unlikely to be stable! * The majority of natural food w ebs are large, complex, and stationary
- n population dynamical
time scales. The majority of natural food w ebs are large, complex, and stationary
- n population dynamical
time scales.
* May R. Will a large complex system be stable? Nature 238 1972
SLIDE 7
Complexity or stability?!
Large and complex systems are in general unlikely to be stable! * Large and complex systems are in general unlikely to be stable! * The majority of natural food w ebs are large, complex, and stationary
- n population dynamical
time scales. The majority of natural food w ebs are large, complex, and stationary
- n population dynamical
time scales.
* May R. Will a large complex system be stable? Nature 238 1972
What are the properties of food webs which give them their unusual stability?
SLIDE 8
- large and complex networks
- many variables
- many parameters
- little informations
- strong nonlinearities
- dynamics on different time scales
Food webs:
SLIDE 9
* Gross T. and Feudel U.: Generalized models as a universal approach to the analysis of nonlinear dynamical systems PHYSICAL REVIEW E 73, 016205 2006
*
Generalized Models
SLIDE 10
SLIDE 11
SLIDE 12
SLIDE 13
SLIDE 14
SLIDE 15
SLIDE 16
SLIDE 17
SLIDE 18
SLIDE 19
µ
SLIDE 20
µ µ µ
SLIDE 21
µ µ
Rate of biomass turnover Sensitivity of production
- r loss on species density
µ
SLIDE 22
SLIDE 23
Use an algorithm to
create realistic topologies (The Niche Model* )
* Williams R.J . & Martinez N.D. Simple rules yield complex food webs Nature 404 2000
SLIDE 24
SLIDE 25
Results
* Thilo Gross, Lars Rudolf, Simon A. Levin and Ulf Dieckmann: Generalized Models Reveal Stabilizing Factors in Food Webs Science 325, 747 (2009)
SLIDE 26
Complexity and stability
SLIDE 27
SLIDE 28
Weak links:
- low flow interactions
- prey centric normalization
Stabilizing for small w ebs, but destabilizing for larger (realistic size) w ebs. “Amount of weak links”
SLIDE 29
SLIDE 30
“trophic size”
?
SLIDE 31
“trophic size”
?
SLIDE 32
Conclusion
SLIDE 33
Conclusion
SLIDE 34
We reproduce: New results: New results:
SLIDE 35
We reproduce: New results: New results:
SLIDE 36
We reproduce: New results: New results:
SLIDE 37
We reproduce: New results: New results:
SLIDE 38
We reproduce: New results: New results:
Thank you for your attention.
SLIDE 39
SLIDE 40
SLIDE 41
Proportion of stable webs Connectance times species number