Metapopulations

Question 1

Define a metapopulation.

Answer 1

A group of spatially separated populations of the same species that interact at some level.

Question 2

What are ‘patches’?

Answer 2

Areas of actual or possible occupation. Patches may be filled or awaiting to be recolonized by the metapopulation.

Question 3

There are 4 characteristic spatial structures of metapopulation. What are they?

Answer 3

1. Classic
2. Core-satellite
3. Patchy
4. Non-equilibrium

Question 4

Explain the structure of a classic metapopulation.

Answer 4

There are multiple patches with low-level connectance. Some patches are occupied and some await re-colonisation.

Question 5

Explain the structure of a core-satellite metapopulation.

Answer 5

There is a large mainland population with many smaller ‘sinks’. The sinks are likely to go extinct and need constant re-colonisation from the mainland.

Question 6

Explain the structure of a patchy metapopulation.

Answer 6

Lots of dispersal between many smaller patches. All patches are always occupied.

Question 7

Explain the structure of a non-equilibrium metapopulation.

Answer 7

There are lots of isolated patches but no dispersal, leading to extinction.

Question 8

What are ‘patches’?

Answer 8

Areas of actual or possible occupation. Patches may be filled or awaiting re-colonisation by the metapopulation.

Question 9

If metapopulations inhabit discrete patches, is there a high risk of extinction?

Answer 9

Yes: migration and re-colonisation is essential for maintaining metapopulations.

Question 10

What kind of landscapes do metapopulations inhabit?

Answer 10

Dynamic, heterogenic landscapes.

Question 11

Metapopulations are said to have asynchronous dynamics. Why?

Answer 11

Because patches are constantly going extinct then being recolonized.

Question 12

Levins in 1970 came up with the following equation for patch extinction:

E = eP

Explain the terms.

Answer 12

E = patch extinction
e = extinction rate
P = proportion of occupied patches

Question 13

Levins in 1970 came up with the following equation for colonisation:

C = mP(1 - P)

Explain the terms.

Answer 13

C = colonisation
m = migration rate
P = proportion of occupied patches

Question 14

The two equations by Levin in 1970 can be combined into:

dP/dt = mP(1 - P) - eP

What does this equation convey?

Answer 14

dP/dt = no. of patches occupied at a certain time, which is patch colonisation minus extinction rate.

Question 15

At equilibrium what does dP/dt equal?

Answer 15

0

Question 16

When dP/dt = 0 you can multiply out the equation and get 1 - e/m = P^. What is P^?

Answer 16

Proportion of colonised patches at equilibrium.

Question 17

There are always some empty patches. True or false?

Answer 17

True.

Question 18

When is there extinction?

Answer 18

When e = m.

Question 19

Why is metapopulation theory useful in conversation?

Answer 19

Just because a patch is not currently being occupied doesn’t mean it won’t be in the future, thus it should be conserved.

Question 20

If there is a high rate of colonisation, what can be said about extinction rate?

Answer 20

It is low.

Question 21

What does it mean to say a patch is occupied?

Answer 21

There is at least 1 individual living there.

Question 22

What are some assumptions about patches? List 4.

Answer 22

1. Patches are the same size
2. Patches are equally connected
3. Extinction in each patch is independent and constant
4. Dispersal is constant and not a function of population size

Question 23

What can be said about all the patch assumptions?

Answer 23

They are unrealistic.

Question 24

If a patch is smaller we assume there are less individuals living there than in a larger patch. True or false?

Answer 24

True.

Question 25

Which is more affected by demographic stochasticity, small or large populations?

Answer 25

Small.

Question 26

Which is more affected by demographic/environmental stochasticity, small or large populations?

Answer 26

Small.

Question 27

Nearest neighbour analyses can be performed on metapopulations to assess inter-patch relations. What information would this tell us?

Answer 27

Spatial distribution, e.g. average inter-patch distance etc.

Question 28

Some patches stay unoccupied. Why?

Answer 28

Limited dispersal.

Question 29

Habitat heterogeneity may reduce the probability of patch extinction. How?

Answer 29

In a small patch the habitat is less likely to be variable, thus any stochasticity will affect the whole area. In a larger patch there is likely to be heterogeneity, and stochasticity will not affect the whole area, leaving refuges for organisms to persist in.

Question 30

The same environmental conditions can have varying effects on organisms in different life stages. Give an example of this.

Answer 30

Bush crickets: Juvenile crickets need high vegetation to protect them from the sun. Older crickets need lower levels of vegetation because it retains water, and wet conditions lower fecundity.

Question 31

Connectivity has a threshold. In a fragmented landscape what happens to levels of dispersal?

Answer 31

Dispersal is greatly reduced.

Question 32

Connectivity has a threshold level. If it falls below this level, there is no connectivity. True or false?

Answer 32

True.

Question 33

What is percolation theory? Explain it in the context of connectivity.

Answer 33

Seeks to explain why populations clump in random environments. Percolation theory often comes into play when there is a fragmented landscape, reducing connectivity and leading to extinction of patches, thus the ones that are left are clumped together.

Question 34

What is an 'edge habitat'?

Answer 34

The edges of the patches. The habitat on the edge will be different to that in the centre.

Question 35

What effect does habitat loss have on edge habitat?

Answer 35

Habitat loss increases edge habitat.

Question 36

Define the edge effect.

Answer 36

Edge habitat is often lower in quality than core habitat. For example organisms may need a large radius of territory but if they live on the edge of the patch then this is not possible.

Question 37

There is higher mortality and turnover in edge habitat than core habitat. True or false?

Answer 37

True.

Question 38

Give an example of higher mortality in an edge habitat.

Answer 38

Trees are more exposed and more likely to be brought down in storms or exposed to herbivores.

Question 39

Is there more or less edge habitat in an irregular-shaped patch?

Answer 39

More edge habitat.