BI111 Lecture Notes - Lecture 9: Parasitoid Wasp, Crataegus, Rhagoletis

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2 Feb 2016
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Lecture 9 – Friday January 22, 2016
Allopatric Speciation
Most common/uncontroversial way that sub-divided populations
can speciate
Relies on geographic isolation
Reproductive Isolating Mechanisms (Prevent Gene Flow
Between Species)
Individuals meet
oTemporal, ecological, behavioural isolation
oPre-zygotic isolating mechanism
oEx. mating calls can change and di"er
Gametes meet
oMechanical isolation
oPre-zygotic isolating mechanism
oEx. divergence selection
Zygotes form and develop
oGamete mortality
oPost-zygotic isolating mechanism
oEx. zygotes die early on
O"spring born
oHybrid inviability
oPost-zygotic isolating mechanism
O"spring fertile
oHybrid sterility
oPost-zygotic isolating mechanism
Sexual Selection Can Lead to Speciation
Parapatric Speciation
There’s a spectrum, and some animals have traits that make
them better suited to live in one part of the spectrum
oEx. there is a temperature gradient in a river, and some
*sh can only live in the cold parts, and others in the warm
parts
Selection keeps hybrids from each other
Cons
oPerhaps this is just secondary contact between allopatric
populations
Rhagoletis pomonella
Life History
Host plants:
Malus
vs.
Crataegus
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