Lecture 11: Populations: Dynamics of consumer-resource populations Flashcards
what have ecologists developed to study the dynamics of population growth and structure
three classes of spatially explicit models
3 modeling approaches with increasing level of complexity
- metapopulation models
- source-sink model
- landscape model
define metapopulation model
Describe a set of subpopulations occupying patches of habitat that individuals move between
define source-sink model
adds information habitat quality in
different patches to metapopulation model
define landscape model
Adds information on the differences in habitat within the habitat matrix - how surrounding habitat improves to source-sink
what does the metapopulation model measure
“patch occupation” through time
what does the source-sink model add to the metapopulation model
quality and directional movement data
what does the landscape model add to the source-sink model
data on habitat and barriers that alter movement
2 main sets of processes that the metapopulation has
- Growth and regulation of subpopulations – each subpopulation may have its own birth and death rates and growth dynamics.
- Colonization of empty patches and the extinction of existing occupied patches
what do metapopulation models capture
the dynamics of patch occupation and overall metapopulation persistence through time
factors impacting subpopulation dynaimcs
- Density-independent events have greater impact on small populations
- density-dependent factors
- movement between populations as a buffer
explain movement between populations as a buffer
- The more individuals move between subpopulations, the more subpopulation dynamics mirror the dynamics of the full population
- Zero or very little movement means each subpopulation has independent dynamics
- At intermediate movement, subpopulations go extinct but are then recolonized, creating a shifting mosaic of patch occupation
metapopulation model equation
pe = 1 - (e / c)
explain the metapopulation model equation
- pe = equilibrium proportion of occupied patches
- e = extinction rate of patches
- c = colonization rate of patches
metapopulation model equation - what happens when e < c
- the equilibrium population is positive
- this means the population is surviving
metapopulation model equation - what happens when e > c
the overall occupancy will decline to 0
metapopulation model equation - more complex/realistic models do what?
elaborate on the e and c parameters
Dynamics can be influenced significantly by incorporating the following factors into e & c terms:
- Different patch sizes within a metapopulation.
- Different rates of colonization for each patch.
- Different dispersal from each patch.
- Inter-dependent patch colonization and extinction rates
define rescue effect
The extent to which migration from large, productive patches can prevent small, unproductive patches from going extinct
what can have a big impact on population dynamics
- being eaten
- consumer population can limit the resource population
what are the consumer-resource interactions
- Predator-prey.
- Herbivore-plant.
- Pathogen/parasite-host.
how does the population cycle in regard to predator-prey interaction
- As the prey population gets bigger, its easier for predators to see and catch
- As the predator population grows, it starts to deplete prey, but time delay in reproduction
what is cycling driven by
a combination of time delays, overshooting, and density-dependent effects in both predator and prey
how do you get regular cycling
the more closely 1:1 predator-prey interaction is approximated, the closer to regulars cycling
what is the Lotka-Volterra model used for
used to predict the oscillations in the size of predator and prey populations
what is the Lotka-Volterra model describe
predator-prey population interactions.
the Lotka-Volterra model forms what foundation
forms the foundation of predator prey modeling research
Lotka-Volterra model equations
calculate the rate of change of predator and prey populations as each is reciprocally influenced by the other
Lotka-Volterra model equations - prey
[rate if change in the prey population] = [intrinsic growth rate of prey population] – [removal of prey individuals by predators]
Lotka-Volterra model equations - predator
[rate if change in the predator population] = [birth rate determined by prey captured] – [death rate from external factors]
Lotka-Volterra model - isocline lines
stable population sizes for prey and predator, based on the number of the other species in the interaction
Lotka-Volterra model - joint equilibrium point
- point where equilibrium isoclines cross
- point at which populations will not change over time
Lotka-Volterra model - low number of prey and predators
a decrease in the predator population allows an increase in the prey population
Lotka-Volterra model - high number of prey and low number of predators
an increase in the prey population allows in an increase in the predator population
Lotka-Volterra model - high number of prey and predators
an increase in the predator population causes a decline in the prey population
Lotka-Volterra model - low number of prey and high number of predators
a decrease in the prey population causes a decrease in the predator population
Factors stabilizing Lotka-Volterra cycling
- predator inefficiency
- density-dependent limitation
- alternative food sources for the predator
- refuges for the prey at low densities
- reduced time delays in predator responses to changes in prey abundance
Lotka-Volterra cycling - predator inefficiency
prevents prey from being driven down so quickly
Lotka-Volterra cycling - density-dependent limitation
independent of the predator-prey relationship (disease, prey’s resource availability, etc.)
Lotka-Volterra cycling - alternative food sources for the predator
this prevents continued driving down of prey population and crash of predator population
Lotka-Volterra cycling - refuges
availability of predator-free space for the population to recover
Lotka-Volterra cycling - time delay
flattens high peaks and low troughs
