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:
- clines of reproductive isolation
(e.g., Rana pipiens)
- clines with circular overlap
(e.g., Parus major, Ensatina)
- species in statu nascendi
(e.g., Drosophila paulistorum)
- Character displacement
- Synchronic species problems
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- 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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