lecture 20.docx

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18 Apr 2012
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How many genes are involved in reproductive isolation (speciation genes)
Species: taxonomic(morphological) & biological concepts. Taxonomic isn’t used that
much. Reason is like in humans, we don’t say that because of looks that we have
more than 1 species of us. Biological is based on inter fertility (exception is asexual).
2 modes of speciation- founded on geography. Both end in similar end stages
allopatric
- Common to animals and plants
- Uses barrier
- Secondary contact if the barrier is removed, and now no longer can
reproduce
Sympatric
- progenitor and derivative are barrier less.
- Typically there should be gene flow stopping there divergence.
- Relatively small cases in which it occurs. Occurs in plants through polyploidy
Stages where reproductive isolation occurs
Finding mate
Mating and fertilization
Development of zygote, sterility
Survival and growth impaired
RI mechanisms
Premating:
- Preventing of zygote by geographical ecological, temporal behavioral, mechanical
or prevention of gamete fusion.
Postmating:
-inviability, sterility, abnormal development of newborns and as a result there easy
target
-F2 breakdown
Apple maggot fly
-Guy bush and jeff feder
- found on hawthrone bush. Animals specialized to feed on it. humans brought in
apple orchards. Host shift, fly no (apple and hawthorne in same family). Sympatry/
divergence since apple orchard coming. 6 percent.
Doug shemske
Monkey flowers are pollinated by bumble bee and hummingbird. At low evelation,
and high areas have to pollinators in each latitude. When brought into green house
they can be cross bread. Reproductive isolating operate pre ating and as a result
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