Lecture 12 - Island Bio Geography

8/3/2019 Lecture 12 - Island Bio Geography

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Island Biogeography

Equilibrium Theory

Explanation of community structure as afunction of size and distance from species

pool Dispersal

Geographic Isolation

Extinction Makes it applicable to more than true

islands


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Island Biogeography

MacArthur and Wilson used past island

studies to develop the theory

Species-area relationships

Species turnover

Species Isolation


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Species-Area Relationship and Size


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Rare Species and Extinction

Applies to Distance


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Isolation and Species Area


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Species Isolation


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Species Isolation


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Species Turnover


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Species Turnover


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Species Turnover


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Equilibrium Theory of Island Biogeography


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Criticisms of Island Biogeography

Interspecific differences and speciesinteractions

Assumed immigration, extinction, and turnover

as stochastic Species richness not composition

Interdependence of immigration andextinction

Treated as independent processes

Does not account for recruitment of newindividuals already on island


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Biogeographically meaningful measures of

isolation

Sometimes difficult to identify source without

studying systematics

Composition question

Biogeographically meaningful measures of

island size Spatial heterogeneity

Ecological and biogeographical history


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Importance of speciation

If species are derived on island, then model is

violated

Speciation probably only important on large,

isolated islands in terms of number of species

Disturbance (ecological and geological time

scales) Would prevent equilibrium


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Tests of Island Biogeography

Estimates of turnover on southern California Channel Islands


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Krakatau RevisitedColonization Curves


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Krakatau RevisitedI/E rates


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Krakatau RevisitedI/E rates


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Simberloff and Wilson (1970) Experiment


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Krakatoa RevisitedPlant Colonization

Succession had to

proceed to allow

animal colonization


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Accounting for Succession/Recruitment

How does succession

alter likelihood that

immigrants will

survive andreproduce?

F = failure rate

(species failing to est.

breeding population

C = IF

C decreases over time


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Disturbance Events

How to account for

disturbance effects?

Disturbanes at same

temporal scale asisland I and E might

prevent equilibrium

Shorter time scale

(fires, drought..)

probably only slow

process


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Possible Effects of Speciation

Effect of Area

Effect of Distance


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Island Applications of Island Biogeography

Freshwater Lakes

North American lakes (Post-Pleistocene)

relied on connections to other waters,

including streams and rivers, for

colonization

Not near saturation

ExampleGreat Lakes; large but not many

species; lotic sources depauparate


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Island Applications of Island Biogeography

African lakesmuch older; high diversity

from speciation through adaptive radiation

North American lakes, including Great

Lakes, show evidence of same but not much

time has passed


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Species-Area

Relationships


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Species-Area Relationship in Rivers

Greater diversity in N.

Amer. rivers

N. Amer. rivers

generally have N-S flow Would allow dispersal

in advance of glaciers

Lecture 12 - Island Bio Geography

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