BIO 258 Notes
WEEK #8.
SPECIES AND SPECIATION

• Geographic variation (Futuyma ch. 15; Minkoff Ch. 13; E21).
  • Importance of geographic variation
  • Occurence of (or absence of) geographic variation
  • Gene flow at ecotones
    example: mine entrances (Antonovics)
  • Altitudinal "races"
  • Insular & continental patterns
• Clines, subspecies and species (E22)
  • Subspecies and polytypic species; pocket gophers and other examples
  • Clines
  • Hybrids
• Species definitions: morphological, biological
  • biological species definition
  • reproductive isolation
  • reproductive isolating mechanisms (premating, postmating)
  • example: mallards and pintails
  • sibling species
  __________
• What is speciation?
  • Phyletic transformation (anagenetic; no new RIM)
  • True speciation or splitting (cladogenetic; new RIM must evolve)
• Geographic speciation. (Futuyma ch. 16; Minkoff Ch. 14; E23)
  • Stages of geographic speciation.
  • Incomplete speciation:
    1. clines of reproductive isolation (e.g., Rana pipiens)
    2. clines with circular overlap (e.g., Parus major,   Ensatina)
    3. species in statu nascendi (e.g., Drosophila paulistorum)
  • Character displacement
  • Synchronic species problems
  __________
• Alternative models of speciation. (E24)
  • SUDDEN speciation:
    • Genic (DeVries, Goldschmidt)
    • Chromosomal: aneuploidy? (no);   polyploidy (esp. in higher plants)
  • GRADUAL speciation:
    • Sympatric speciation (claimed in various cases)
    • Nonsympatric speciation (spectrum of possibilities):
      • Parapatric
      • Alloparapatric
      • Allopatric:
        • by crossing pre-existing barriers
        • with new barriers developing
        • by extinction of intervening populations in a cline
      • ?Symparapatric ("stasipatric")
  • allochronic species problems
• Hybridism and polyploidy. (Minkoff Ch. 15).
  • hybridism and its effects
  • speciation by polyploidy

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