lecture20 - BioEE 278 Evolutionary Biology Fall 2007...

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BioEE 278 Fall 2007 Evolutionary Biology Lecture 20 MODELS OF SPECIATION Reading: Ch. 16, pp. 379 - 1 st paragraph 390, pp. 392 (bottom)-399 (skip 1 st two paragraphs of 394) A. Fundamental issues in speciation. 1. The geography of speciation. a. do speciation events require geographic isolation of the diverging populations? b. traditional classification of speciation events relies on geography: allopatric and sympatric speciation c. really a continuum - how much gene flow can be tolerated and still get divergence? 2. Role of natural selection. a. what role does natural selection play in the divergence of populations? b. are barriers to gene exchange "molded" by natural selection or are they simply a fortuitous consequence (by-product) of divergence in isolation? 3. Genetic architecture. a. number, effect (large or small), and chromosomal distribution of genes that are responsible for reproductive isolation B. Models of speciation. 1. Allopatric speciation:vicariance and founder effect models. a. both involve geographic isolation b. vicariance - an event that divides the range of a species into two or more isolated units c. example: napping shrimp on Carribean and Pacific sides of the Isthmus of Panama d. founder event model: divergence occurs in small isolated population (perhaps due to genetic drift) - speciation involves a population bottleneck e. founder events may occur most often in populations that are "peripheral isolates" -
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This note was uploaded on 09/28/2008 for the course BIOEE 2780 taught by Professor Geber during the Fall '07 term at Cornell University (Engineering School).

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lecture20 - BioEE 278 Evolutionary Biology Fall 2007...

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