EE Lecture 31: Metapopulations

Question 1

define metapopn

Answer 1

a set of spatially isolated popns linked to one another by dispersal

Question 2

what are metapopns characterized by

Answer 2

repeated extinctions and colonizations

Question 3

why are the popns of some species prone to extinction

Answer 3

1) the patchiness of their habitat makes dispersal between pops difficult
2) enviro condns often chnage in an unpredictable and rapid manner

Question 4

outline conclusions of Huffakers experiments

Answer 4

although the individual popns may be prone to extinction, the collection of popns (the metapopns) persists because it includes popns that are going extinct and new popns that are established by colonization
RANDOM EXTINCTIONS AND COLONIZATIONS

Question 5

represent popn eqtn for metapopns - Levins model

Answer 5

dp/dt = cp (1 - p) - ep
p - proportion of habitat patches occupied at time t
c-colonization
e-extinction

Question 6

what is the rescue effect of metapopns

Answer 6

extinction occurs in individual patches but then these patches are rescued by immigration - recolonization - so the whole metapopn persists even though no patch is stable

Question 7

why does a metapopn persist even though no patch is stable

Answer 7

because of the recolonization rescue effect, where if a popn goes extinct - the patches will get recolonized by immigration

Question 8

for a metapopn to persist for a long time, what must the e/c ratio be

Answer 8

less than 1

Question 9

give an example of a metapopn in nature

Answer 9

voles in Tvarminne archipelago.
the larch budmoth, Zeiraphera diniana
repeated immigration
emigration and extinction cant treat as one popn

Question 10

what is Levins model

Answer 10

dp/dt = cp (1 - p) - ep

Question 11

what is the eqbm patch occupancy rate for Levins metapopn model

Answer 11

p = 1 - e/c

Question 12

according to Levins model, when would the metapopn go extinct

Answer 12

when e > c

Question 13

what does Levins model assume

Answer 13

1. infinite patches equally connected
2. all patches have equal chance of receiving colonists, so spatial arrangements of patches doesnt matter
3. all patches have an equal chance of extinction
4. once a patch is colonized, its popn increases to its carrying capactiy more rapidly than the rates at which extinction and colonization occur

Question 14

what is habitat fragmentation

Answer 14

anthropogenic effects converting large tracts of habitat into a set of spatially isolated habitat frgments causing a species to have a metapopn structure when it didnt have one before

Question 15

why is huffakers experiment not realisticq

Answer 15

all patches equally and equally connected - not true in reality
habitat patch area and distance from other patches related to the probability of patch being occupied in a given year

Question 16

what did Carl Huffaker experiment on

Answer 16

oranges to determine metapopns
citrus mite and predatory mite
took oranges in isolation -changed distances between them by separation with plastic balls - patch quality adjusted by covering parts of oranges
each field was a separate universe
RESULT:
cpredator prey coexistance can be facilitated by spatial structure
you see prolonged cycles
extinction and colonization play a key role in dynamics and persistance

Question 17

give an example of how metapopns might exist in nature

Answer 17

n.alaska - group of lakes, sometimes connected to one another by temporary streams that form after the snow melts or after periods of heavy rainfall

Question 18

what are the 2 important features of metapopns to consider

Answer 18

1. isolation by distance

2. the effect of patch area - small patches harder to colonize

Question 19

in metapopns what is a good quality patch called

which individuals here

Answer 19

good quality patch - source

most competitive individuals here

Question 20

in metapopns whats a bad quality patch called

which individuals here

Answer 20

sink

less competitive individuals here

Question 21

which patch will have the most competitive individuals

Answer 21

a source

Question 22

which is better - less comp individuals to not breed at all, or to go to the sink

Answer 22

to go to the sink