Lecture 22 - Dispersal, Metapopulations And Island Biogeography

True Or False: Real populations are closed systems

False, they’re not

Definition Of Dispersal

Individuals that can move from one population to another

3 Benefits Of Dispersal

1. Colonize New Areas

2. Escape Competition

3. Avoid Inbreeding

Post Glacial Colonization Depends On Plant & Animal _______

Dispersal

Definition: Metapopulation

Spacially separated populations connected by dispersal

True Or False: Metapopulations can survive even when individual populations are failing

True

What makes individual unstable groups globally stable?

Dispersal: individuals moving from patch to patch

How is patch dynamics different from population dynamics?

Patch dynamics track patch occupancy through time instead of an individual population

What is the constate rate e?

rate of extinction in a patch population

What is the constant P?

# of occupied patches

What does the expression 1-p refer to?

Fraction of empty patches

What is the constant c?

Colonization constant

What is the colonization rate expression?

cP(1-P)

What is the value of dP/dt @ equilibrium?

0

Say A always outcompetes B within a patch, what is required for global coexistence? (4 things)

• A occasionally goes extinct OR new patches are created

• B must be a better disperser than A

• B must be a good colonizer

• A= better competitor, B= better colonizer (tradeoff)

Explain the example of pikas being a metapopulation

• Pika habitats are isolated but when they become vacant other pikas can relocate there (disperse)

That is what keeps the global population of pikas afloat.

Name 4 ways populations can be driven to extinction

1. Stochasticity: random fluctuations in population numbers

2. competitive exclusion

3. Predators/ parasites

4. extinction because of a very small population size

How Does Coexistence Keep Populations From Going Extinct?

• Predation keeps dominant competitors from completely dominating

• Non equilibrial conditions: patchy habits, migration, competition colonization trade off

Metapopulation Vs. Metacommunity

population -

Set of local populations connected by dispersal

Community - 

Local communities connected by the dispersal of 1 or more other species

3 factors to determine # of species on an island

1. Colonization

2. Extinction

3. In-situ speciation

What Is The Goal Of MacArthur And Wilson’s Theory Of Island Biogeography?

Predict the # of species on an island based on the island’s size & distance from mainland

__________ speciation was ignored in the theory of island biogeography

In situ: New species formed from old ones

Will the extinction rate rise of fall as the # of species increases?

Rise

Near & Big Islands Have ______ Species, Small And Far Species Have ——————- Species

More, Less

According to Prof Muhler’s Research On Anolis Lizards He Concluded That

Large Islands have more species & Isolated islands have fewer species