EE31

Question 1

what is a metapopulation?

Answer 1

a group of spatially separated populations of the same species which interact at some level by immigration and emigration (patchy population)

Question 2

what

did Carl Huffaker’s experiment show ?

Answer 2

predator prey co-existence can be facilitated by spatial structure and the rescue effect

Question 3

what is wrong with Nicholson bailey models describing the dynamics of coupled host-parasite / predator-prey systems?

Answer 3

model is not stable - tiny deviations from equilibrium mean populations crash
could not explain non-extinction population stability

Question 4

what is the context of Huffakers experiment in terms of the mites involved? should the populations persist?

Answer 4

predatory mite is voracious predator of the citrus mite that eats from oranges . Organes are firstly infested with citrus mite then predatory mite follows. Predatory eats citrus mites (they die) then predatory mite dies of starvation. However, in the wild both species persist and do not go extinct. Huffaker’s experiments show this is because spatiall aggregation can be stabilising

Question 5

what was the method to Huffaker’s experiments/

Answer 5

1)fields of oranges and rubber balls
20dispersal distances between oranges adjusted using rubber balls
3)patch quality adjusted by covering portions of oranges
4)sticks added to the oranges to manipulate the mites’ natural dispersal mechanisms

Question 6

what is the rescue effect?

Answer 6

ability of a habitat being rescuable by immigration (recolonisation )

although single orange=unstable the whole system= stable

Question 7

where is extinction in Huffaker’s experiments? in individual patches?

Answer 7

yes. extinction occurs in individual patches

Question 8

what stabilises nicholson-bailey (predator-prey) type interactions ?

Answer 8

spatial structure (aggregations)

metapopulations

Question 9

what is the result summanry of Huffaker’s experiments? (3)

Answer 9

Clear demonstration that predator-prey coexistence can be facilitated by spatial structure

You see prolonged cycles overall (total population)

Extinction and colonization play a key role here in dynamics and persistence

Question 10

what did the field mole in Tvärminne archipelago case study show?

Answer 10

Spatial aspect important

repeated immigration emigration extinction

Independent dynamics but emmigration links the populations

Cannot treat this as one population!

Question 11

where are the field moles?

Answer 11

Tvärminne archipelago

Question 12

What does the larch budmoth case study show?

Answer 12

• outbreaks in waves/immigration
• evidence for cycles go back to tree rings in Roman times

The Larch budmoth: defoliates trees throughout the European alps

Parasitoids of the budmoth

Question 13

What are Levin’s model assumptions? (5)

Answer 13

• infinite number of patches
• patches are equivalent
• patches are equally connected
• colonisation is not affected by distance
• patches are in a binary state 1 or 0 (no consideration of local population dynamics or pop abundance)

Question 14

What was levin interested in?

Answer 14

exploring effect of occupied/empty patches (binary state- open or occupied only)

he looked at the balance between local system extinction and colonisation.

Question 15

what is levin’s model?

Answer 15

dP/Dt = cp(1-p) - ep

c=colonisation rate
p=occupancy
e=extinction rate
dp/dt=rate of change of fraction of patches occupied

Question 16

what is p when dp/dt= 0 (equilibrium patch occupancy state)?

Answer 16

p=1-e/c

Question 17

if e>c then p

Answer 17

metapopulation goes extinct

Question 18

if e

Answer 18

p>0 so the metapopulation survives even though over time each patch will eventually go extinct

Question 19

what happens to c if some habitat patches are removed? effect on pop?

Answer 19

c is reduced, pop more likely to go extinct

Question 20

what happens to c if wildlife corridors are added e.g hedges? EFFECT ON POP?

Answer 20

c is increased. population persistence is more likely

Question 21

what 2 things did lenvins model shows wrt proportionality?

Answer 21

1) extinction is proportional to occupancy

2) colonisation is proportional to p*(1-p)

Question 22

what is p(t)?

Answer 22

the fraction of patched currently occupied at time (t) by the species of interest.

Question 23

Lenvins model flaw= not all patches are equal and equally connected, give an example

Answer 23

Skipper butterfly
Hesperia comma (skipper butterfly)
-only lives in certain grassland
-only lays eggs on certain size of certain grass species

Question 24

what is the effect of patch size and remoteness?

Answer 24

Small patches go extinct more frequently

Remote patches colonized less readily

Question 25

what is the link between good quality patch(source) , migration and bad quality (sink)

Answer 25

such a system CAN BE EVOLUTIONARY STABLE

source;most competitive,good quality

sink: less competitive individuals here, bad quality
note: it is better for competitive individual to move back to the bad quality patch (the sink) than to not breed at all

Question 26

example of source sink dynamic? would the population survive in isolation?

Answer 26

Cakile edentula
annual plant on seashores in Martinque Bay, Nova Scotia

by the shore -Seed production high
Mortality low
Net disperser of
seeds

landward-Seed production low Mortality high Net receiver of
seeds

Population stable here, although it would not survive in isolation

Question 27

Back to the moles, explain their population dynamics wrt emigration and patches

Answer 27

small populations can “rescue” large

emigration increases before extinction

Patches not equal but metapopulation roughly follow Levins model

Question 28

are source-sink patch quality dynamics the only ones?

Answer 28

No. There are many other configurations besides one source and one sink.
Patch-quality effects are more than just source-sink dynamics

Question 29

are within patch dynamics important?

Answer 29

yes.The Levins model is only a “patch occupancy” model
Each patch is either inhabited or not
No population dynamics within patches
Clearly dynamics do occur within patches
The Huffaker experiments made this clear
Within-patch dynamics can be important!

YOU COULD ADD Lotka-Volterra dynamics

Question 30

Problems with metapopulation models:

Answer 30

Patch occupancy or within-patch dynamics model?

Patches homogeneous in terms of size and quality? Or heterogeneous?

Patches homogeneous in terms of remoteness? Or is there spatial structure?

Question 31

What is the Glanville fritillary an example of?

Answer 31

a well studied system with much complexity. It is a butterfly population. Also gene for dispersal propensity shows another limitation in that ecologists often forget genetics

Question 32

what is the Glanville fritillary

Answer 32

Butterfly metapopulation, Aland islands, Finland

Has two host plants: the plantain, Plantago lanceolata and the speedwell, Veronica spicata

Question 33

as patch size increased in glanville fritillary what happened to extinction probability?

Answer 33

extinction probabilty declined

Question 34

What does the habitat mapping of the glanville fritillary show wrt patches?

Answer 34

some areas have many nearby patches

Some have few, distant patches

Also, some patches are larger/better than others

Question 35

what is the purist definition of metapopulations?

Answer 35

1) chance of extinction and recolonization on each oatch
2) dynamics of populations shouldn’t be too related (synchrony)
3) dynamics of pops shouldn’t be completetly independednt

Question 36

what to geneticists think needs to be considered? more

Answer 36

inbreeding- increases extinction risk

Question 37

why do we need a metapopulation perspective?

Answer 37

if a population as a whole functions as a metapopulation then the rates of subpopulation extinction and colonization may be of importance.