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III. Island Biogeography. III. Island Biogeography. Biogeography : The study of the distribution of organisms in space and time. Biogeography looks at four fundamental processes:.

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III. Island Biogeography

Biogeography: The study of the distribution of organisms in space and time.


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Biogeography looks at four fundamental processes:

1. Dispersal: Movement of organism(s) from a point of origin (= location of source, or ancestral, population) to a new location.

2. Colonization: Organism reaches new location, survives, reproduces, and establishes new population.

3. Extinction: Species is eliminated from a particular area (i.e., no more reproducing individuals present); species may survive elsewhere, and may re-colonize area where it went extinct.

4. Evolution: Surviving population in a particular area undergoes change(s) in frequency of gene alleles; may result in altered phenotype, and, given sufficient time, possibly the formation of new species (= speciation).


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Islands are important natural laboratories for the study of biogeography, ecology, population genetics, evolutionary biology, etc.


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Early naturalists ( biogeography, ecology, population genetics, evolutionary biology, e.g., 16th-18th centuries)

exploring isolated islands noted new types

of plants and animals, which were often

distinctive for each island or island group.For several centuries, scientific focus was on

cataloging the diversity of island organisms.



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…including 13 species of GalapagosGalapagos Finches


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1859 - Publication of Galapagos“On the Origin of Species”

Darwin speculated on possible means by which organisms colonized islands and evolved into new species (e.g., Galapagos finches)



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Half of Krakatau was blown away; remaining portion, Rakata (a volcanic cone), plus neighboring islands, left covered with 30-60 m of pumice and ash (= sterile landscape?).


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Rakata and adjacent islands formed a laboratory for study of island colonization and tropical succession:

  • May 1884 - first researchers reach the islands; find only a spider in a crevice on the south side of Rakata.

  • October 1884 - grass shoots growing on Rakata.


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  • 1886 - Botanists, and later zoologists, begin monitoring colonization of Rakata:

  • nine species of flowering plants present on beaches;

  • 1897 - 23 species of flowing plants present;

  • development of coastal forest provided seeds and fruits for colonizing bats and birds;

  • ferns (with spores that can be dispersed by wind) were first colonizers away from the coast;


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  • colonization by new plant species was initially high, then dropped as available space became occupied by pioneer species;

  • immigration rate then increased as

  • developing forests created new habitat (= potential new ecological niches);

  • as forests replaced grasslands, grasses, and insects and birds dependent on grasses, became extinct on island.


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  • Biogeographical lessons from Krakatau: dropped as available space became occupied by pioneer species;

  • Composition of plant and animal communities

  • at any given time reflect

  • colonization

  • local extinction

  • succession

  • disturbance


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  • *e.g., Whittaker, R.J. et al. 1992 GeoJournal 28.2: 201-211.

  • Whittaker, R.J. et al. 2000,J. Biogeograpy 27(5):1049-1064


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  • Dr. Koning will discuss this…stay tuned


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    Types of Islands patterns and mechanisms of evolution of island flora and fauna.


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    Continental Islands patterns and mechanisms of evolution of island flora and fauna. : Formed on continent; may have formerly been connected to mainland by land bridge:

    Island

    Current Sea Level

    Former

    Sea Level

    Continent

    Submerged Land Bridge

    Continental Shelf


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    Examples of Continental Islands patterns and mechanisms of evolution of island flora and fauna.

    British Isles

    California Channel Islands

    Block Island, Nantucket, Martha’s Vineyard


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    British Isles patterns and mechanisms of evolution of island flora and fauna. : Land mass is part of European continent. During the last ice age, Britain was connected to Europe by a plateau called Doggerland.

    Doggerland

    Source: New Scientist, 8 Nov. 2008


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    As Ice Age ended, rising sea level flooded Doggerland and formed English Channel.

    Dogger Bank, an upland area of Doggerland, outlined in red.

    North Sea

    England

    France


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    California Channel Islands: formed English Channel.Group of eight islands off the California coast; during last ice age, some were connected to mainland by land bridge.


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    Block Island, Nantucket, Martha’s Vineyard: formed English Channel.Coastal wedge sediment islands formed by glacial deposits (terminal/recessional moraines); probably no dry, passable connection to mainland since last Ice Age. Long Island is also of this type.

    Click to Play Animation

    http://www.uwsp.edu/gEo/faculty/lemke/glacial_processes/MoraineMovie.html


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    Continental Islands: formed English Channel.Two Unusual Cases

    1. San Salvador’s offshore cays: Rising sea level caused

    erosion of San Salvador, leaving many small, erosion-

    Resistant islands, or cays (“keys”).


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    Cays on the horizon (arrow) were once formed English Channel.part of San Salvador.


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    Continental Islands: formed English Channel.Two Unusual Cases

    • 1. San Salvador’s offshore cays: Rising sea level caused

    • erosion of San Salvador, leaving many small, erosion-

    • resistant islands, or cays (“keys”).

    • 2. Terrestrial habitat islands: Isolated region on larger

    • land mass, such as

    • mountain top;

    • forest remnant surrounded cleared land;

    • forest remnant on island in river or lake;

    • water-filled tree hole in forest


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    Barrow Colorado Island (BCI): A 1500 hectare remnant of lowland moist forest in the middle of the Panama Canal; it is managed by the Smithsonian Institute as a tropical research site.


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    B. lowland moist forest in the middle of the Panama Canal; it is Oceanic Islands: Never connected to continent; usually formed by volcanic activity and isolated from continent by deep ocean.

    Oceanic Island

    Current Sea Level

    Former Sea Level

    Continental Shelf

    Undersea

    Volcano

    Sea Floor


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    Examples of Oceanic Islands lowland moist forest in the middle of the Panama Canal; it is

    • Iceland

    • Japan

    • Aleutians

    • Bermuda

    • Caribbean Islands

    • Hawaiian Islands

    • South Pacific Atolls

    • Et al.



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    Oceanic Islands: subduction zone.Two Unusual Cases

    New Zealand


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    New Zealand: subduction zone.Landmass represents the highlands of a submerged continent called Zealandia. South Island straddles two lithospheric plates and subduction zone.


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    Oceanic Islands: subduction zone.Two Unusual Cases

    New Zealand

    Bahamas



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    LandSat Image of San Salvador Island subduction zone.

    • San Salvador sits on isolated portion of Bahamas Platform

    • Surrounded by deep ocean

    • Never connected to other Bahamian Bank islands, or to continent

    • Qualifies as an oceanic island


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    End of Slide Show subduction zone.4/13/09Refer to Handouts for Remainder of Lecture


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