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Lecture 8

BIO120H1 Lecture Notes - Lecture 8: Metapopulation, Santa Catalina Mountains

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James Thomson

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Lecture 8: Metapopulations, plant community composition
Fender’s blue butterfly had been rediscovered. Willamette valley, Oregon, prairie
Depends on lupine, females disperse, find that plant, put caterpillars on the plant so they can grow
Ecobeaker simulation model
Spatial map of habitat with 2 types of vegetation: prairie and farm. Butterfly’s caterpillars survive only in
prairie. Butterflies must discover prairie or will die without reproducing. Smaller patches of prairie
cannot handle population of butterflies so they go extinct. Little patch can keep going if there is a big
population in the neighborhood by migration
Conclusion: a bigger patch can help out to a patch that is going to extinction by rescue/migration
Andy Smith, Bodie, California Pika research. Pika populations in tailing pile are good pika habitat.
Prefer rocky habitat
What is % of patches with pika?
1) North patch network: high, stable, anchored by big reservoirs
2) Middle: low, extinction/renewal
3) South: marginal, in decline
From metapopulation model:
1) High, stable
2) Low,stable
3) Unstable
Patches are connected by migration -> uncoupled the patches:
1) Doing well, source, dispersing population to middle and south populaiton
2) Sink population, goes extinct without source population
3) Sink
Metapopulation how organisms in the area connected to the rest of the world
Model population drive extinct in several ways:
- Strong density-dependence
- Unstable competition
- Unstable predator-prey
- Allee effects at low density
In real life these tendencies are smoothened by non-equilibrium conditions, habitat patchiness, rescue-
by-migration, variation in life-history strategy
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