BioEE 278
Fall 2007
Evolutionary Biology
Lecture 21
CASE HISTORIES OF SPECIATION
Reading:
A. Adaptive radiations on “islands”
1. Examples: Darwin’s finches, Hawaiian radiations (many insects and plants), cichlids in
African Rift Lakes
2. What is it about islands?
3. What are the advantages of studying islands?
B. Hawaiian Silverswords
1. Geographic context of Hawaii
2. Mainland origins and monophyletic group with 3 genera
3. Rapid diversification in ~5 MY
4. Rapid evolution of regulatory genes involved in flower differentiation and photosynthesis
5. Morphological differentiation by habitat – convergent evolution
6. Allopatric vs. sympatric speciation – basal species on Kaui (oldest island); degree of sympatric
speciation declines with island age.
C. Hawaiian “spiny-leg” spiders in genus
Tetragnatha
1. Monophyletic clade in the genus
2. Four “ecomorphs” associated with different predation habit
3. Island distribution of ecomorphs
4. How many times have ecomorphs evolved and what was the geographic context?
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- Fall '07
- GEBER
- Evolution, sympatric speciation declines, A. Adaptive radiations
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