continental vs. oceanic islandsonline.sfsu.edu/bholzman/_private/316/island biogeography.pdf ·...

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1 Dr. Barbara Holzman Island Biogeography Islands Continental/Oceanic Problems/ Issues Access/Isolation Habitat Hazards Theory of Island Biogeography MacArthur and Wilson Problems w/ theory Natural Reserve Planning Continental vs. Oceanic Islands Continental islands Continental islands are bodies of land that are connected by the continental shelf to a continent. That is, these islands are part of an adjacent continent and are located on the continental shelf of that continent. Ex. Greenland, Barbados, Trinidad, Sicily, Sumatra, New Guinea, Tasmania. Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman For the exclusive use of students enrolled in Geog 316.01 Fall 2006

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Dr. Barbara Holzman

Island BiogeographyIslandsContinental/Oceanic

Problems/ IssuesAccess/IsolationHabitatHazards

Theory of Island BiogeographyMacArthur and Wilson

Problems w/ theory

Natural Reserve Planning

Continental vs. Oceanic Islands

Continental islandsContinental islands are bodies of land that are connected by the

continental shelf to a continent. That is, these islands are part of an adjacent continent and are located on the continental shelf of that continent. Ex. Greenland, Barbados, Trinidad, Sicily, Sumatra, New Guinea, Tasmania.

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

2

Oceanic Islands• islands that are not

part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

Volcanic islandsVolcanic islands are built by volcanoes, not geologically part of any

continent. One type of volcanic island is found in a volcanic island arc. These islands arise from volcanoes where the subduction of one plate under another is occurring. Ex. Mariana Islands, Aleutian Islands, Tonga, etc.

Another type of volcanic island occurs where an oceanic rift reaches the surface. Ex. Iceland.

The last type of volcanic island are those formed over volcanic hotspots. A hot spot is more or less stationary relative to the moving tectonic plate above it, so a chain of islands results as the plate drifts. Ex. Hawaiian Islands,

1) Nature of the island biotaHow does it differ from the source area(s)?What is the nature of the immigrants that allowed them to reach and colonize the island?

Concepts/Issues

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

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2) Identify and quantify the factors that control:- Rate at which new species reach an island- Rate at which species become extinct on an

island- Number of species an island can support

3) Process of evolutionary change by which an island becomes an integrated ecosystem- Each organism adapted to physical andbiological aspects of its life on the island- Occupation of niches

Islands and ColonizationFactors:

Dispersal abilities of immigrants Galapagos Islands: 60% by bird, 30% by wind, 9% drifted by sea

• Diversity of habitats: less than 9 hectares = BEACH/ latitude, elevation, etc.

• Isolation -- How far from source? How rich is source?

• Hazards – Hurricanes, volcanoes, humans

• Ability to adaptgene poolfounder effect – small population w/ little genetic variability

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

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Number of Species and Area (reptiles/amphibians)

Island Area and Diversity (flora)

Island Area and Diversity

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

5

Founder Effect

Founder effect and bottlenecks

Tiburon Island, Mexico

Elephant seals

Amish (extra digit)

Q. Victoria Hemophilia

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

6

Evolution UncheckedGigantism: Giant tortoise, Elephant bird, Komodo dragon,

Dwarfism:Mouse lemur, pygmy mammoth, Madagascar kingfisher

Urocyon littoralis

Channel Islands Fox• weighs approximately 1.8 kilograms

• smallest fox species in the United States

• predators: golden eagles, humans

Loss of flight

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

7

Relics

Published in 1967

Theory of Island BiogeographyNumber of species on an island depends on a number of factors:

• area (topography assumed)

• diversity of habitat

• accessibility to colonists

• richness of source

I.B. add…• equilibrium between rate of colonizationby new species and extinction of existing species

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

8

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

9

Equilibrium predictedS=CAZ

S = number of speciesA= areaC=

History of Rakata higher plant flora since 1883

Modes of dispersal

Rates of immigration and extinction

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

10

Effect of Island Size:

Large Islands have a higher equilibrium number of species

Effect of Distance From the Mainland:• Near Islands have a higher rate of colonization• Near Islands have a higher equilibrium number of species

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

11

Problems with the IB Theory

• Its applicability to all organisms is in question

• Simply looking at physical characteristics is limited (i.e. area/isolation)

• Equilibrium can only be maintained in a constant environment (not with climatic disturbances/ envir. changes/ humans)

• Quantitative attempt simplifies process

Where Can We Find "Islands"?

•Oceanic Islands –Arise from volcanic activity; Galapagos and Hawaii•Continental Islands –Islands that were once contiguous with the mainland; Aleutians/Channel Islands•Agricultural Fields•Caves•Fragmented Forests Mountaintops•Hosts (Parasites see hosts as islands)•Ponds/ Streams•Cities (fragmented landscapes)

Application of Island Biogeography The Theory of Island Biogeography has been used in the creation of nature reserves, designing habitat and determining the number of species a habitat can viably carry. Although there are many shortcomings of the quantitative nature of the theory, some of this work has been helpful.

Nature Reserves•Design of nature reserves can lead to problems

•How big is big enough?

•SLOSS

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

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SLOSS: Single large or several small???

• Single large

• Several small

• Connectivity

Application of Island Biogeography To "Habitat Islands"Habitat diversity confounds affects of area "Edge Effect" on habitat islands Degree of Isolation in habitat islands may be difficult

to assess

Corridors

Roadless Areas betweenYellowstone and Grizzly Park

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006

13

Why Do We Care About Island Biogeography?

"Insularity is a universal feature of Biogeography."- (MacArthur and Wilson. 1967 )

•Applicability of Island Biogeography Models to other "Islands"

•Island Biogeography and evolution can lead toendemic species

• Conservation Biology • Fragmented Landscape • High number of Island Endemics 34% of US listed species are from Hawaiian Islands or Puerto Rico

Island BiogeographyIslandsContinental/Oceanic

Problems/ IssuesAccess/IsolationHabitatHazards

Theory of Island BiogeographyMacArthur and Wilson

Problems w/ theory

Natural Reserve Planning

Assignment

Geog 316: Biogeography SFSU Fall 2006 Dr. B.A. Holzman

For the exclusive use of students enrolled in Geog 316.01 Fall 2006