1. Metapopulations I. So far, we have looked at populations with
the assumption of geographic closure:
no immigration, no emigration
What if we relax that assumption?

2. What is a metapopulation?
“Set of local populations occupying an
array of habitat patches and linked by
the movements of individuals”
Movement: emigration and immigration
not back-and-forth movements
of individuals

4. Example of metapopulation: spotted owls in southern CA
(Ricklefs and Miller 2000 p. 331)

5. Origin The term was first used by Richard Levins in 1969 and 1970
Levins’ model looked at patch occupancy:
colonization and extinction events
Also known as the “classical” model or
“blinking light” model
What was the persistence time of the
metapopulation overall?

6. Does the idea work? Many species seem to have a
metapopulation structure….
Bull Trout
Butterflies
Pool Frogs
Acorn Woodpeckers
Pikas
Furbish’s Lousewort

7. Different kinds of patchy populations….
Classic metapopulation (Levins)
Mainland-island metapopulation
migrant flow from big patch to small
Patchy population (too much migration
for a metapopulation)
Separate populations (no migration at all,
or very little)

8. An illustration:
(from Harrison and Taylor 1997)

9. A closer look at the classical model
dP/dt = mP(1-P) – eP
P: number of occupied patches
e: extinction rate
m: colonization rate

10. The assumptions of the classical metapopulation model
Growth, regulation, and other dynamics
of local populations ignored
Colonization and extinction events are
instantaneous (no growth/decline phase)
All patches equally likely to receive new
immigrants (“midfield assumption”)
Patches are all the same size and quality

11. The classical model Immigrants only matter when they
colonize an empty patch
Is a patch occupied, or not?
How long will the metapopulation persist?

12. What if we add some realism?
Most of the time, the distance between
patches does matter
Size also matters- patch size and distance
from another patch also interact
Isolated patches that are also large are
relatively more likely to be occupied
than small isolated patches

13. Example of size/density interaction
Glanville fritillary butterfly
(Ricklefs and Miller 2000 p. 333)

14. Example of size/isolation interaction
Common shrew
(sorex araneus)
(Ricklefs and Miller 2000, p. 335)

15. The Rescue Effect Populations may be saved from
extinction by arrival of immigrants
Example: acorn woodpecker population
in New Mexico

16. Acorn Woodpeckers Population persistence depends on immigrants
from populations whose
dynamics vary independently

17. Source-sink dynamics Some patches are inherently better
quality than others
These patches support growing
populations that produce emigrants
Other patches are poorer quality,
and populations can only be
maintained by immigration

18. Example: Eastern Kingbird
Metapopulation in Charlotte Valley, NY
Inhabited upland, floodplain, and riparian
zone habitats
Demographic rates and movements
among breeding populations were
studied for 10 years
M. Murphy Cons. Biol. 15:

19. Example: Eastern Kingbirds
Survival was highest
in floodplain, but
productivity was
lowest there
Riparian subpopulation was stable, but
other two were declining
(M. Murphy Ecology 82: )

20. Example: Eastern Kingbirds
Modeling suggested
that metapopulation
overall is a sink.
If riparian survival
Increased slightly, the
Entire metapopulation would be sustained.
(M. Murphy, Cons Biol. 15: )

21. Example: Eastern Kingbirds
Murphy suggested
that creek habitat acted
as a “pseudosink”
A pseudosink is a patch with density-
dependent effects on demographic rates
so it seems unsustainable; if density
declined, demographic rates would improve

22. Another Example Demographic rates in a patch may vary
not only with density, but with
environmental conditions-
A patch may be a source one year,
and a sink the next.
Burrowing owls at NAS Lemoore, CA

23. Burrowing owls (again)
(Gervais 2002)