ted carmichael swarmfest 2015 presentation
TRANSCRIPT
- 1. Population Dynamics: The Red Queen Effect and Attractors in Evolution Ted Carmichael SwarmFest July 11, 2015
- 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. 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. 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. 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. 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. 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. 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. The Red Queen Hypothesis Success rate reduced by 1/3rd. Turns per tick reduced by 1/3rd.
- 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. Conclusions: Thank you!
- 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.