Population Dynamics:
The Red Queen Effect and
Attractors in Evolution
Ted Carmichael – SwarmFest – July 11, 2015
Outline
• Introducing the General Ecosystem model
• Assumptions of the model
• Demo: Stepped pattern of biomass accrual
• ...
The Marine Ecosystem Model
Three trophic levels:
• Food
• Prey (Fish)
• Predators
Model assumptions:
• Both predators and ...
The Marine Ecosystem Model
Validation: Lotka-Volterra, Gause's Law,
Paradox of Enrichment, Stepped
pattern of biomass accr...
The Marine Ecosystem Model
Stepped pattern of biomass accrual
• Oksanen, et. al, 1981
• Mathematical predictions of popula...
Considerations for Field Studies
Average Age is an important attribute
●
Can give us important inferences on existent popu...
The Red Queen Hypothesis
“Now, here, you see, it takes all the running you can do, to
keep in the same place.” -Through th...
The Red Queen Hypothesis
Another piece of the evolutionary puzzle … the effects on
predator and prey populations via two d...
The Red Queen Hypothesis
“Success rate”
reduced by 1/3rd.
“Turns per tick”
reduced by 1/3rd.
Conclusions:
●
There are many non-intuitive results, even in a very
simple model of population dynamics
●
Average age for ...
Conclusions:
Thank you!
The Competitive Exclusion Principle
The competitive exclusion principle states that two (or
more) species competing for th...
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Ted Carmichael swarmfest 2015 presentation

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Predator Prey dynamics with a generative ABM

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Ted Carmichael swarmfest 2015 presentation

  1. 1. Population Dynamics: The Red Queen Effect and Attractors in Evolution Ted Carmichael – SwarmFest – July 11, 2015
  2. 2. Outline • Introducing the General Ecosystem model • Assumptions of the model • Demo: Stepped pattern of biomass accrual • Considerations for field studies • The Red Queen Hypothesis • Predators: Effects of Effectiveness • Impacts on Evolutionary Pressures
  3. 3. The Marine Ecosystem Model Three trophic levels: • Food • Prey (Fish) • Predators Model assumptions: • Both predators and prey reproduce as a function of how much they eat. • Completely homogeneous environment. • The agents move randomly and eat once per turn if there is food available. • All agents have a limited “lifetime.”
  4. 4. The Marine Ecosystem Model Validation: Lotka-Volterra, Gause's Law, Paradox of Enrichment, Stepped pattern of biomass accrual • Carmichael & Hadzikadic, Advances in Complex Systems, 2013
  5. 5. The Marine Ecosystem Model Stepped pattern of biomass accrual • Oksanen, et. al, 1981 • Mathematical predictions of population changes based on changes in primary enrichment Model Assumption: prey have a constant supply of food. - what happens if the food supply changes? Demo: increasing the food supply to the prey. What happens? Will: 1) the prey population increase? 2) the predator population increase? 3) both prey and predator increase in population size?
  6. 6. Considerations for Field Studies Average Age is an important attribute ● Can give us important inferences on existent populations ● Rarely collected systematically ● Replacement rate and equilibrium population
  7. 7. The Red Queen Hypothesis “Now, here, you see, it takes all the running you can do, to keep in the same place.” -Through the Looking Glass ● “Arms race” between predators and prey ● Assuming the current state is a “basin of attraction,” and the arms race reaches a terminus, what accounts for the trade-offs that prevent further advancements? ● Diversity among prey – old, young, sick, unlucky ● Prey sharing … leads to cooperative strategies, which leads to “free riders,” which limits positive evolution ● Anything else?
  8. 8. The Red Queen Hypothesis Another piece of the evolutionary puzzle … the effects on predator and prey populations via two different methods of reducing predator effectiveness: ● Decrease the “success rate” of predators: i.e., sometimes the predators try to eat a prey but “miss” (the prey escapes) ● Reduce the “turns per tick” of the predators, from 6 to 4. Predators will live longer … 600 “turns” across more “ticks”
  9. 9. The Red Queen Hypothesis “Success rate” reduced by 1/3rd. “Turns per tick” reduced by 1/3rd.
  10. 10. Conclusions: ● There are many non-intuitive results, even in a very simple model of population dynamics ● Average age for a population is important, and may help infer attributes (such as consumption rate) that cannot easily be gathered ● Not all efficiency gains produce population-level benefits, and some may even be detrimental to a species ● Some of these non-intuitive results may help explain evolutionary pressures on a species
  11. 11. Conclusions: Thank you!
  12. 12. The Competitive Exclusion Principle The competitive exclusion principle states that two (or more) species competing for the same resources, and sharing the same predators, cannot continually co- exist if all other ecological factors are constant.

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