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2nd Year: Ecology > Metapopulations > Flashcards

Metapopulations Flashcards

1
Q

Define a metapopulation.

A

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

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2
Q

What are ‘patches’?

A

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

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3
Q

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

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

Explain the structure of a classic metapopulation.

A

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

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5
Q

Explain the structure of a core-satellite metapopulation.

A

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.

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6
Q

Explain the structure of a patchy metapopulation.

A

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

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7
Q

Explain the structure of a non-equilibrium metapopulation.

A

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

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8
Q

What are ‘patches’?

A

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

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9
Q

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

A

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

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10
Q

What kind of landscapes do metapopulations inhabit?

A

Dynamic, heterogenic landscapes.

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11
Q

Metapopulations are said to have asynchronous dynamics. Why?

A

Because patches are constantly going extinct then being recolonized.

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12
Q

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

E = eP

Explain the terms.

A 
E = patch extinction
e = extinction rate
P = proportion of occupied patches
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13
Q

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

C = mP(1 - P)

Explain the terms.

A 
C = colonisation
m = migration rate
P = proportion of occupied patches
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14
Q

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

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

What does this equation convey?

A

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

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15
Q

At equilibrium what does dP/dt equal?

A

0

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16
Q

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

A

Proportion of colonised patches at equilibrium.

17
Q

There are always some empty patches. True or false?

A

True.

18
Q

When is there extinction?

A

When e = m.

19
Q

Why is metapopulation theory useful in conversation?

A

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

20
Q

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

A

It is low.

21
Q

What does it mean to say a patch is occupied?

A

There is at least 1 individual living there.

22
Q

What are some assumptions about patches? List 4.

A
  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
23
Q

What can be said about all the patch assumptions?

A

They are unrealistic.

24
Q

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

A

True.

25
Q

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

A

Small.

26
Q

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

A

Small.

27
Q

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

A

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

28
Q

Some patches stay unoccupied. Why?

A

Limited dispersal.

29
Q

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

A

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.

30
Q

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

A

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.

31
Q

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

A

Dispersal is greatly reduced.

32
Q

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

A

True.

33
Q

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

A

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.

34
Q

What is an ‘edge habitat’?

A

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

35
Q

What effect does habitat loss have on edge habitat?

A

Habitat loss increases edge habitat.

36
Q

Define the edge effect.

A

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.

37
Q

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

A

True.

38
Q

Give an example of higher mortality in an edge habitat.

A

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

39
Q

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

A

More edge habitat.

2nd Year: Ecology (13 decks)

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