The Roots of Current Distributions

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Explaining patterns of disjunctions

  1. Historical approaches
      Fossils / Panbiogeography
  2. Ecological/Evolutionary approaches
      cladistic
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    History of Lineages

    • History of lineage (cladistics) [tetrapods]
    • History of fossils (paleontology) [dinosaurs]
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Phylogenetic Systematics

http://lsvl.la.asu.edu/bio470/jfouquette/Outlines/012.phylog.classif.html next






Cladogram Example Plate Tectonics

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    Cladogram - Example Homonids


          Cladogram       Area Cladogram

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Molecular Phylogenetics (systematics)

  • Cladistics based on DNA and RNA mutations
  • Rates of mutations vary
    • Bramuda grass (nuclear) 3.8 x 10-7 /nucleotide/year [r]
    • Drosophila (nuclear) 1.1-1.5 x 10-8 /nucleotide/year [r]
    • Homo X-chromosome 1.5 × 10-9 /nucleotide/year [r]
    • Homo X-chromosome 7.2 x 10-10 /nucleotide/year [r]
    • 5S rRNA 1.0-1.8 x 10-10 /nucleotide/year [r]
    • Brassica mDNA neutral 3.57-11.71 x 10-13 /nucleotide/year [.]
    • Brassica mDNA nad4 1.14-1.64 x 10-13 /nucleotide/year [.]
  • Hominina Example
  • overview
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Limitations of Cladistic Classification

  • equally parsimonious cladograms exist
  • reticulate evolution of plants violates assumptions
  • viral transfer of genetic material violates assumptions
  • results of Cladistic Classification are sometimes different from the fossil record
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    Cladistics & Disjunctions

    • Dispersal
        Single Organism
    • Barriers (Vicariance: separation by barriers)
      • Many unrelated organism
      • Shared disjunctions
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    Vicariance and Plate Tectonics

    • Barriers
        Atlantic Ocean
        Europe = N. America until Eocene
    • Noah's Arks
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    Phylogenetic biogeography

    • Area Cladogram - pattern due to phylogeny
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    Cladistic Biogeography

    • Area Cladogram - pattern due to shared taxa

      hylid frogs, ratite birds,
      and xylontine fishes

      1. based on taxonomy - genus, species
      2. or based on characters rather than taxonomy
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  • Panbiogeography

      Leon Croizat
        1952-1964 Venezuela
        panbiogeography: distantly-related ("unrelated") 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

    Consensus Area Cladograms (endemics) next






    Historical Biogeography - Hawaiian example

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