BIO-0014 Lecture 9: Speciation - Synpatric

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1. Allopatric speciation
a.
i. Colonizing events can lead to speciation
ii. When there is a physical barrier, variance occurs
iii. Eg. researchers compared the DNA sequences of trumpeters from
different areas of the Amazon basin to the geological events that occurred
1.
2.
2. Isolation and Divergence in Sympatry
a. Populations that live in the same area as opposed to different areas (allopatry)
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i.
b. Process is common in bacteria
i. Less constrained by the homogenizing effects of sexual reproduction
ii. Prone to comparatively dramatic and rapid genetic change through
horizontal gene transfer
c. Multicellular eukaryotic organisms, sympatric speciation is a plausible process
that is known to occur, but the frequency with which is has occurred is less clear
d. How does this happen?
i. Can be initiated by two events
1. External events
a. Disruptive selection based on different ecological niches or
mate preferences
b. Intermediate phenotypes are selected against and extreme
phenotypes become more desirable
c.
d. Based on niche
i. Range of ecological resources that a species can
use and the range of conditions it can tolerate
e. Even though sympatric populations are not geographically
isolated
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