Lecture 11: Populations: Dynamics of consumer-resource populations

Question 1

what have ecologists developed to study the dynamics of population growth and structure

Answer 1

three classes of spatially explicit models

Question 2

3 modeling approaches with increasing level of complexity

Answer 2

1. metapopulation models
2. source-sink model
3. landscape model

Question 3

define metapopulation model

Answer 3

Describe a set of subpopulations occupying patches of habitat that individuals move between

Question 4

define source-sink model

Answer 4

adds information habitat quality in
different patches to metapopulation model

Question 5

define landscape model

Answer 5

Adds information on the differences in habitat within the habitat matrix - how surrounding habitat improves to source-sink

Question 6

what does the metapopulation model measure

Answer 6

“patch occupation” through time

Question 7

what does the source-sink model add to the metapopulation model

Answer 7

quality and directional movement data

Question 8

what does the landscape model add to the source-sink model

Answer 8

data on habitat and barriers that alter movement

Question 9

2 main sets of processes that the metapopulation has

Answer 9

• 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

Question 10

what do metapopulation models capture

Answer 10

the dynamics of patch occupation and overall metapopulation persistence through time

Question 11

factors impacting subpopulation dynaimcs

Answer 11

1. Density-independent events have greater impact on small populations
2. density-dependent factors
3. movement between populations as a buffer

Question 12

explain movement between populations as a buffer

Answer 12

• 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

Question 13

metapopulation model equation

Answer 13

pe = 1 - (e / c)

Question 14

explain the metapopulation model equation

Answer 14

• pe = equilibrium proportion of occupied patches
• e = extinction rate of patches
• c = colonization rate of patches

Question 15

metapopulation model equation - what happens when e < c

Answer 15

• the equilibrium population is positive
• this means the population is surviving

Question 16

metapopulation model equation - what happens when e > c

Answer 16

the overall occupancy will decline to 0

Question 17

metapopulation model equation - more complex/realistic models do what?

Answer 17

elaborate on the e and c parameters

Question 18

Dynamics can be influenced significantly by incorporating the following factors into e & c terms:

Answer 18

1. Different patch sizes within a metapopulation.
2. Different rates of colonization for each patch.
3. Different dispersal from each patch.
4. Inter-dependent patch colonization and extinction rates

Question 19

define rescue effect

Answer 19

The extent to which migration from large, productive patches can prevent small, unproductive patches from going extinct

Question 20

what can have a big impact on population dynamics

Answer 20

• being eaten
• consumer population can limit the resource population

Question 21

what are the consumer-resource interactions

Answer 21

• Predator-prey.
• Herbivore-plant.
• Pathogen/parasite-host.

Question 22

how does the population cycle in regard to predator-prey interaction

Answer 22

• 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

Question 23

what is cycling driven by

Answer 23

a combination of time delays, overshooting, and density-dependent effects in both predator and prey

Question 24

how do you get regular cycling

Answer 24

the more closely 1:1 predator-prey interaction is approximated, the closer to regulars cycling

Question 25

what is the Lotka-Volterra model used for

Answer 25

used to predict the oscillations in the size of predator and prey populations

Question 26

what is the Lotka-Volterra model describe

Answer 26

predator-prey population interactions.

Question 27

the Lotka-Volterra model forms what foundation

Answer 27

forms the foundation of predator prey modeling research

Question 28

Lotka-Volterra model equations

Answer 28

calculate the rate of change of predator and prey populations as each is reciprocally influenced by the other

Question 29

Lotka-Volterra model equations - prey

Answer 29

[rate if change in the prey population] = [intrinsic growth rate of prey population] – [removal of prey individuals by predators]

Question 30

Lotka-Volterra model equations - predator

Answer 30

[rate if change in the predator population] = [birth rate determined by prey captured] – [death rate from external factors]

Question 31

Lotka-Volterra model - isocline lines

Answer 31

stable population sizes for prey and predator, based on the number of the other species in the interaction

Question 32

Lotka-Volterra model - joint equilibrium point

Answer 32

• point where equilibrium isoclines cross
• point at which populations will not change over time

Question 33

Lotka-Volterra model - low number of prey and predators

Answer 33

a decrease in the predator population allows an increase in the prey population

Question 34

Lotka-Volterra model - high number of prey and low number of predators

Answer 34

an increase in the prey population allows in an increase in the predator population

Question 35

Lotka-Volterra model - high number of prey and predators

Answer 35

an increase in the predator population causes a decline in the prey population

Question 36

Lotka-Volterra model - low number of prey and high number of predators

Answer 36

a decrease in the prey population causes a decrease in the predator population

Question 37

Factors stabilizing Lotka-Volterra cycling

Answer 37

• 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

Question 38

Lotka-Volterra cycling - predator inefficiency

Answer 38

prevents prey from being driven down so quickly

Question 39

Lotka-Volterra cycling - density-dependent limitation

Answer 39

independent of the predator-prey relationship (disease, prey’s resource availability, etc.)

Question 40

Lotka-Volterra cycling - alternative food sources for the predator

Answer 40

this prevents continued driving down of prey population and crash of predator population

Question 41

Lotka-Volterra cycling - refuges

Answer 41

availability of predator-free space for the population to recover

Question 42

Lotka-Volterra cycling - time delay

Answer 42

flattens high peaks and low troughs