metapopulations i
DESCRIPTION
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?. What is a metapopulation?. “Set of local populations occupying an array of habitat patches and linked by - PowerPoint PPT PresentationTRANSCRIPT
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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?
![Page 2: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/2.jpg)
What is a metapopulation?
“Set of local populations occupying anarray of habitat patches and linked bythe movements of individuals”
Movement: emigration and immigrationnot back-and-forth movementsof individuals
![Page 3: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/3.jpg)
![Page 4: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/4.jpg)
Example of metapopulation: spotted owls in southern CA
(Ricklefs and Miller 2000 p. 331)
![Page 5: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/5.jpg)
Origin
The term was first used by RichardLevins 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 themetapopulation overall?
![Page 6: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/6.jpg)
Does the idea work?
Many species seem to have ametapopulation structure….
Butterflies
Pool Frogs
Furbish’s LousewortPikas
Bull Trout
Acorn Woodpeckers
![Page 7: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/7.jpg)
Different kinds of patchy populations….
•Classic metapopulation (Levins)
•Mainland-island metapopulationmigrant flow from big patch to small
•Patchy population (too much migrationfor a metapopulation)
•Separate populations (no migration at all,or very little)
![Page 8: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/8.jpg)
An illustration:
(from Harrison and Taylor 1997)
![Page 9: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/9.jpg)
A closer look at the classical model
dP/dt = mP(1-P) – eP
P: number of occupied patches
e: extinction rate
m: colonization rate
![Page 10: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/10.jpg)
The assumptions of the classicalmetapopulation model
•Growth, regulation, and other dynamicsof local populations ignored
•Colonization and extinction events areinstantaneous (no growth/decline phase)
•All patches equally likely to receive newimmigrants (“midfield assumption”)
•Patches are all the same size and quality
![Page 11: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/11.jpg)
The classical model
Immigrants only matter when they colonize an empty patch
Is a patch occupied, or not?
How long will the metapopulation persist?
![Page 12: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/12.jpg)
What if we add some realism?
Most of the time, the distance betweenpatches does matter
Size also matters- patch size and distancefrom another patch also interact
Isolated patches that are also large arerelatively more likely to be occupiedthan small isolated patches
![Page 13: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/13.jpg)
Example of size/density interaction
Glanville fritillary butterfly
(Ricklefs and Miller 2000 p. 333)
![Page 14: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/14.jpg)
Example of size/isolation interaction
Common shrew(sorex araneus)
(Ricklefs and Miller 2000, p. 335)
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The Rescue Effect
Populations may be saved fromextinction by arrival of immigrants
Example: acorn woodpecker populationin New Mexico
![Page 16: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/16.jpg)
Acorn Woodpeckers
Population persistencedepends on immigrantsfrom populations whose
dynamics vary independently
![Page 17: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/17.jpg)
Source-sink dynamics
Some patches are inherently betterquality than others
These patches support growingpopulations that produce emigrants
Other patches are poorer quality,and populations can only bemaintained by immigration
![Page 18: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/18.jpg)
Example: Eastern Kingbird
Metapopulation in Charlotte Valley, NY
Inhabited upland, floodplain, and riparianzone habitats
Demographic rates and movementsamong breeding populations werestudied for 10 years
M. Murphy. 2000. Cons. Biol. 15:737-748.
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Example: Eastern Kingbirds
Survival was highestin floodplain, butproductivity waslowest there
Riparian subpopulation was stable, butother two were declining
(M. Murphy. 2001. Ecology 82:1304-1318)
![Page 20: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/20.jpg)
Example: Eastern Kingbirds
Modeling suggestedthat metapopulationoverall is a sink.
If riparian survival Increased slightly, the
Entire metapopulation would be sustained.
(M. Murphy, 2001. Cons Biol. 15:737-748)
![Page 21: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/21.jpg)
Example: Eastern Kingbirds
Murphy suggestedthat creek habitat actedas a “pseudosink”
A pseudosink is a patch with density-dependent effects on demographic ratesso it seems unsustainable; if densitydeclined, demographic rates would improve
![Page 22: Metapopulations I](https://reader035.vdocuments.us/reader035/viewer/2022062314/5681334a550346895d9a4cd7/html5/thumbnails/22.jpg)
Another Example
Demographic rates in a patch may varynot 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
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Burrowing owls (again)
Population Growth of Burrowing Owls
0
10
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60
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1997 1998 1999 2000
Year
Nu
mb
er o
f N
ests
0
0.3
0.6
0.9
1.2
1.5Number of Nests
Population growth rate
(Gervais 2002)