Chapter 12, Centers of Origin, Vicariance Biogeography

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Reconstructing Biogeographic Histories:
    History of Earth > Interpreting Biogeographic Patterns

    History of Earth < Patterns of Distributions
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CENTERS OF ORIGIN

  1. which regions are cradles of evolution
  2. how have biotas (provinces) assembled
  3. thirteen criteria of Cain (1944)
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Example of "Centers of Origin"

sea snakes Hydrophiidae (50 sp.)
  • Traceable
    • Restricted by temperature 20 oC
    • Cenozoic origin
    • Distributions overlap with nearest relatives (Elapidae, cobras)
    • Intermediate forms trace speciation
  • Australian-New Guinea origin
    • Highest diversity (30 sp.)
    • Location of closest relatives
    • Most primitive genus in New Guinea
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Issues of Centers of origin

  1. basic assumption is the 13 criteria
      unproven scenarios
  2. tropical vs. arctic origins
      both have been assumed to be centers
  3. "unproven just-so stories" without verification
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Panbiogeography

    Leon Croizat
      1952-1964 Venezuela
      panbiogeography: distantly-related taxa have similar disjunction patterns

      Patterns are due to contraction of the former ranges

      Emphasis on multiple taxa rather than single group (cf. center)

      Tracks
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    Hennig's Progression Rule

      As clades diversify, plesiomorphic traits dominate at centers of origin

      The "most displaced" member of the clade will have the most apomorphic traits

      (not always true camels)

      area cladogram
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    Vicariance Biogeography (American Museum Group)

      Combines (borrows)
      • Hennig's emphasis on cladistics
      • Croizat's emphasis of endemism and disjunction of multiple taxa
      Contrasts
      • Dispersal Biogeography: migration across barriers (seldom - never)
      • Vicariance Biogeography: barriers arise to disrupt distributions
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Vicariance Biogeography

    Area Cladogram Barriers correspond to nodes of cladogram

    Vicariance Methods & Concept
    • Dispersal hypothesis "impossible" to falsify
    • Unlikely for several different organisms to disperse together
    • Multiple dispersals (by same organism) and extinctions destroy cladogram "hypothesis"

    South America

    Parasites
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Historical Biogeography

  1. rigorous logic and hypothesis testing
  2. rigorous phylogenetic systematics
  3. use of area cladograms
  4. emphasis on fossil data
Darters Example

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Hawaiian example

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