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![Page 1: Macroecological questions. What patterns exist, and how are they determined by environment vs. history? How are ecosystems structured, and how is this.](https://reader035.fdocuments.in/reader035/viewer/2022062412/5a4d1b097f8b9ab05998996c/html5/thumbnails/1.jpg)
Macroecological questions.
• What patterns exist, and how are they determined by environment vs. history?
• How are ecosystems structured, and how is this structure shaped by evolution?
• What is the relationship between structure and function?
• What are the robustness and resilience properties of ecosystems and how are they shaped by evolution?
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HOT features of ecosystems • Organisms are constantly challenged by environmental
uncertainties,• And have evolved a diversity of mechanisms to minimize
the consequences by exploiting the regularities in the uncertainty.
• The resulting specialization, modularity, structure, and redundancy leads to high densities and high throughputs,
• But increased sensitivity to novel perturbations not included in evolutionary history.
• Robust, yet fragile!• Complex engineering systems are
similar.
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Uncertainty and
RobustnessComplexity
Interconnection/FeedbackDynamics
Hierarchical/Multiscale
HeterogeneousNonlinearity
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Uncertainty and
RobustnessComplexity
Interconnection/FeedbackDynamics
Hierarchical/Multiscale
HeterogeneousNonlinearity
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Homogeneous Heterogeneous
Tight
Loose
coup
ling
Ideal gas
Internet
Post office
Turbulent Shear flows Power
grid
Organisms
Ecosystems
Telephone system
Socio-economic systems
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Internet
Organisms
Ecosystems
Homogeneous Heterogeneous
Tight
Loose
coup
ling
Idealgas
Postoffice
TurbulentShear flows
HOTTelephone system
Power grid
Socio-economic systems
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Internet
Organisms
Ecosystems
Homogeneous Heterogeneous
Tight
Loose
coup
ling
Idealgas
Postoffice
TurbulentShear flows
ComplexityTelephone
system
Power grid
Socio-economic systems
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Internet
Organisms
Ecosystems
Idealgas
Postoffice
TurbulentShear flows
Socio-economicsystems
Complexity
Telephone system
Power grid
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Internet
Organisms
Ecosystems
Ideal gas
TurbulentShear flows
“Complexity”
Telephone system
All
None
desi
gn
Phase transitions
HOT
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1 dimension
All
None
desi
gnControl Theory
Statistical Physics
Dynamical Systems
Information TheoryComputational
Complexity
Theory ofComplex systems?
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Universal network behavior?
demand
throughputCongestion
induced “phase
transition.”
Similar for:• Power grid?• Freeway traffic?• Gene regulation?• Ecosystems?• Finance?
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random networks
log(thru-put)
log(demand)
Networks Making a “random network:”• Remove protocols
– No IP routing– No TCP congestion control
• Broadcast everything Many orders of magnitude
slower
BroadcastNetwork
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Networks
random networks
real networks
HOTlog(thru-put)
log(demand)
BroadcastNetwork
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random
designed
HOTYield,flow, …
Densities, pressure,…
The yield/density curve predicted using random ensembles is way off.
Similar for:• Power grid• Freeway traffic• Gene regulation• Ecosystems• Finance?
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HOT
Turbulence
Log(flow)
log(pressure drop)
random pipes
streamlined pipes
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Ecosystems?
random food webs
real food webs
HOT“through-
put?”
“density?”
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random food webs
real food webs
HOT“throughput?”• reproduction• carbon• biomass
“density?”• Genes• Cells• Neurons• Organisms
May: generic complexity destabilizes models
butecosystems are not random
collections of organisms
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HOT features of ecosystems
• Organisms are constantly challenged by environmental uncertainties,
• And have evolved a diversity of mechanisms to minimize the consequences by exploiting the regularities in the uncertainty.
• The resulting specialization, modularity, structure, and redundancy leads to high densities and high throughputs,
• But increased sensitivity to novel perturbations not included in evolutionary history.
• Robust, yet fragile!
![Page 19: Macroecological questions. What patterns exist, and how are they determined by environment vs. history? How are ecosystems structured, and how is this.](https://reader035.fdocuments.in/reader035/viewer/2022062412/5a4d1b097f8b9ab05998996c/html5/thumbnails/19.jpg)
Ecosystems and extinction
• 99.9% of all species which have ever existed are now extinct
• Extinction events have heavy tails. • 5 major extinction events and numerous smaller
ones. • Currently in the sixth major extinction with the
rate increasing orders of magnitude in the last 10,000 years.
Observations
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Ecosystems and extinction• There is an ongoing debate about the cause of these
extinctions. • Biologists generally agree that they are due to
catastrophic external events– meteor impacts – large scale geophysical phenomena.
• Advocates of SOC/EOC argue instead that they are due to SOC/EOC “co-evolutionary biological phenomena.”
• But while extinctions may be triggered by exogenous events, the distribution of extinctions for a given disturbance is a fairly structured, deterministic, and even predictable process.
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Habitats
terrestrial vs. marineisland vs. continentaltropical vs
nontropical
greater extinction vulnerability
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Specialization
• Within a habitat, specialization offers short-term benefits.
• Evolution necessarily ignores events that don’t actually happen, even if they are catastrophic. (So do we.)
• Thus tails may be extra heavy.• Specialization consistently correlates with extinction risk
in large extinctions. • For example, body size increases over time on average
(both within and across species).
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Specialization
• Large body size has been a risk factor in all major extinctions (although not always in marine animals).
• However, in the smaller late Eocene extinctions, large-bodied mammal species were not selected against.
• This highlights the role of external causes and the highly structured form of the response, because...
• The late Eocene extinctions were generally related to global cooling, which tends to favor large body size.
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HOT
Disturbance
Evolution and extinction
Specialization
“density?”
“through-put?”
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Ecosystems and extinction• There is an ongoing debate about the cause of the large
extinctions that are known from the fossil record. • Biologists generally agree that they are due to
catastrophic external events– meteor impacts – large scale geophysical phenomena.
• Advocates of SOC/EOC argue instead that they are due to SOC/EOC “co-evolutionary biological phenomena.”
• But while extinctions may be triggered by exogenous events, the distribution of extinctions for a given disturbance is a fairly structured, deterministic, and even predictable process.
![Page 26: Macroecological questions. What patterns exist, and how are they determined by environment vs. history? How are ecosystems structured, and how is this.](https://reader035.fdocuments.in/reader035/viewer/2022062412/5a4d1b097f8b9ab05998996c/html5/thumbnails/26.jpg)
SOC/EOC
HOT
What’s at stake?
If ecosystems are:• EOC/SOC: Specie extinction, global warming,
etc. are random fluctuations. Not to worry, nothing to do. Details don’t matter.
• HOT: Robust, but fragile. Details do matter.