Single-Species Populations IV: Metapopulations and Other Spatially-Structured Populations

Question 1

The spatial ecology of individual small, extinction-prone populations is often

Answer 1

patchy, but not isolated.

Question 2

In individual small, extinction-prone populations, population persistence and dynamics depend on

Answer 2

the capacity of individuals to move and disperse between connected patches.

Question 3

On a landscape scale, population persistence can be explained by

Answer 3

• rates of movement
• colonisation
• extinction
• interactions between these three variables

Question 4

Under logistic growth

Answer 4

• r declines with density
• reflects the ability of density-dependence to regulate an exponentially growing population abouts its environmental carrying capacity

Question 5

r

Answer 5

per capita growth rate

Question 6

Fragmented habitats often display

Answer 6

• small populations undergoing breeding depression
• extinction prone because of the vulnerability of their local population to stochastic events

Question 7

On landscape fragmentation, local population patches are

Answer 7

reduced in area and coupled with high extinction rates and disintegration of social structures

Question 8

From what do high extinction rates arise?

Answer 8

• environmental and demographic stochasticity
• drift
• high heterozygosity
• alee effects

Question 9

Describe recolonisation in an open system

Answer 9

Nt+1 = Nt + Births - Deaths + Immigrants – Emigrants.

Question 10

What are the amoung-population processes

Answer 10

Immigration and emigration

Question 11

Describe the amoung-population processes

Answer 11

• critical to fragmented population persistence
• dispersal ability relative to fragmentation determines population structure and survival

Question 12

In a spatial context, fragmented landscapes sometimes form

Answer 12

metapopulations – populations of populations.

Question 13

A non-equilibrium metapopulation is when

Answer 13

extinction is higher than colonisation, leading to an inevitable, albeit slow, population decline

Question 14

What does metapopulation formation allow?

Answer 14

• species persistence in the landscape as a balance of rates of local extinction and colonisation events between patches
• patches ‘blink’ on off, with colonisation and extinction respectively
• only some of the patches are occupied during any one time slice.

Question 15

Give an example of a non-equilibrium metapopulation

Answer 15

• Meliteaea cinxia, the Glanville Fritillary, found in Åland, Finland
• studied by Hanski, broadly considered the godfather of metapopulation biology

Question 16

Describe Hanski

Answer 16

pioneered the study of dynamic spatial distribution of populations

Question 17

Describe the formalisation and modelling of metapopulations

Answer 17

• Levins
• rate of change of occupied patches = c - e.
• dp/dt = cp(1-p) – ep

Question 18

c

Answer 18

colonisation

Question 19

e

Answer 19

extinction

Question 20

p

Answer 20

patch

Question 21

stable equilibrium of occupied p fraction occurs when

Answer 21

• c = e
• when the differential = 0
• pˆ = 1- e/c

Question 22

Describe Levins analysis

Answer 22

• higher the rate of colonisation and lower the rate of extinction, the greater the proportion of patches that would be occupied
• coser habitat patches ease dispersal and have a higher colonisation rate
• smaller populations more vulnerable to stochastic extinction

Question 23

Describe a phenomenon that increases the chance of landscape-level extinction

Answer 23

correlated population dynamics that mirror each other across fragments

Question 24

Describe how colonisation rates have been maximised

Answer 24

ensuring the geographical closeness and connection of patches

Question 25

Describe uncorrelated population dynamics

Answer 25

• decrease the probability of simultaneous local extinction
• leads to global extinction, across patches
• allow for the dispersal events that allow recolonisation of locally extinct patches

Question 26

Which metapopulations are the most unstable?

Answer 26

correlated metapopulations

Question 27

Give an example of spatial conservation to minimise e rates

Answer 27

• habitat management to increase habitat area and resources (to allow for a corresponding increase in carrying capacity)
• reducing population variations ensuring heterogeneity of patches
• differential management to allow optimisation to different stochastic events reduces population synchrony, maintaining the likelihood of dispersal events to avoid landscape-level extinction

Question 28

Describe how p-hat has been maximised

Answer 28

conservation of empty habitat patches to prepare for potential future colonisation

Question 29

What are metapopulations?

Answer 29

populations of just less than average connectivity and variance in patch size

Question 30

What are non-equilibrium populations?

Answer 30

when patches are highly isolated and the variance in size is mostly small

Question 31

How is population connectivity measured

Answer 31

dispersal distance relative to inner-patch distance

Question 32

What are island-mainland (or core-satellite) populations

Answer 32

highly isolated but with high patch size variance

Question 33

What are patchy panmictic populations?

Answer 33

connectivity is slightly better than in metapopulations, but patch size variance is slightly larger

Question 34

What are dissected populations?

Answer 34

connectivity is high but patch size is still variable

Question 35

Each different fragmented population structure has

Answer 35

different implications for their practical conservation strategies.

Question 36

Describe and give an example of a patchy population

Answer 36

• organisms display high mobility and therefore dispersal is high
• extinction rate is much less than the colonisation rate
• Holly leafminer (Phytomyza ilicis)

Question 37

Describe and give an example of island-mainland dynamics

Answer 37

• Edith’s checkerspot (Euphydras Editha)
• mainland extinction rate is always = 0
• island population, in a spatial sense, can be deemed immortal

Question 38

Describe source-sink dynamics

Answer 38

• source is the net exporter of individuals
• does not receive immigrants, but provides a lot of emigrants
• persistence of the sink can only be explained by its high immigration from the source, otherwise its population would decline towards extinction
• cannot support a barrier being inplaced

Question 39

Describe a sink populations

Answer 39

always exhibits a mortality greater than its natality

Question 40

Give an example of source-sink dynamics

Answer 40

• seed-plant (Cakile edentyka), Sea Ricket populations that live close to the tidelines and require a constant input of seeds near the high watermark
• beach source and dune sink