Lecture XIX - Community Structure

Lecture XIX - Community Structure - Lecture XVIII Community...

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Lecture XVIII – Community Structure
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Ecological Community Evidence of ecological communities exists in abundance, however, the definition of an ecological community is still in debate Two basic and competing views of the nature of communities were developed at the beginning of the century
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Definitions of Community Communities are higher levels of organization for organisms: Fredrick E. Clements (1905): plant communities Victor Shelford (1913): animal communities Communities are loose assemblages of species, coexisting because of adaptations to similar conditions Henry A. Gleason (1926)
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F.E. Clements (and Shelford) Community as a higher organizational unit, comprised of a distinct set of populations of coevolved species: Same set of species tend to be found in association with one another Have discrete boundaries Functions as a unit
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H. A. Gleason Communities as sets of species co-occurring because of adaptations to similar habitats: Species often found in other associations Merge into bordering communities Species function individually
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Species Distribution in Communities These are the ranges of 12 species of trees that occur in a single association in Kentucky None of these distributions are similar, indicating that this community is merely a chance collection of species
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Eastern Deciduous Forest Despite the previous slide, the following communities are structurally similar, with many shared species The upper figure is from SE Missouri, while the lower is from NE Ohio Note the similarities http://www.mvs.usace.army.mil/MarkTwain/rereg%20fall%20colors3.JPG http://tncweeds.ucdavis.edu/products/show01/sl016.jpg
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Modern Concepts Communities occur in many forms, from closed to open, The gleasonian view dominates community ecology Communities are generally groups of individual species whose ranges overlap at the community of interest.
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Modern Concepts Although the gleasonian view dominates community ecology, certain caveats are in order Similar climates and soil types tend to produce communities which are similar in structure, and often in species composition, When the physical environment shows abrupt changes, communities may show sharply defined borders, and, Certain species associations seem to be repeated regularly
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Modern Concepts Communities are viewed, in general, as local chance collections of species, that are the result of climatological and soil conditions, and generally exist on a continuum
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Ecotones When changes between communities or habitats are relatively abrupt, these transition zones are called ecotones . The species living in this
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This note was uploaded on 01/23/2010 for the course BIOS 230 taught by Professor Gibbons during the Fall '08 term at Ill. Chicago.

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Lecture XIX - Community Structure - Lecture XVIII Community...

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