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Lecture 24 - Speciation.docx

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McGill University
Biology (Sci)
BIOL 111
Suzanne Gray

Speciation Three major “species concepts”  Typological (morphological)  Biological  Phylogenetic Problems in Morphology: sexual dimorphism can be quite large and therefore results in problems when it comes to categorizing through morphology  Juveniles were also classified differently than their adult specie Problems with using morphoProblems with using morphology.and female)  Example #2: domestic dogs o Dogs show similar levels of diversity but explore new morphological space A typical perception of the biological species concept is that it doesn’t allow species to interbreed and produce viable offspring. Biological species concept: groups of actually or potentially interbreeding natural populations, which are reproductive isolated from other such groups  Allows for some gene flow  Problems: difficult for allopatric populations and not particularly useful for fossils Speciation is a process: 1. A barrier is established 2. The two populations diverge genetically but are still reproductively compatible 3. Reproductive incompatibility is established Various mechanisms of speciation: 1. Uniform natural selection 2. Divergent natural selection (ecological selection) 3. Genetic drift 4. Polyploidy 5. Hybridization 6. Sexual Selection 7. Cytoplasmic incompatibility Ecological Speciation: 1. Disruptive/divergent selection drives adaptive divergence 2. Reproductive isolation evolves as a consequence Environmental Divgent Adptive Ec coolloggi icaall contrast selection divergence speciation Dispersal Gene
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