Bis2CFall10.Lecture2.extras

Bis2CFall10.Lecture2 - about phylogenetic relationships polytomy Polytomies An extreme case of ignorance a completely unresolved bush polytomy

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F. Relatedness Relatedness 73
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a b c d e f h g Both trees say the same thing: g and h share a more recent common ancestor with each other than either does with f Relative relatedness of taxa is a question of how recent they share common ancestry Present Past Questions of relatedness
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a b c d e f h g Let’s consider: Is taxon e more closely related to d or g? Questions of relatedness
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a b c d e f h g Let’s consider: Is taxon e more closely related to d or g? Questions of relatedness
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a b c d e f h g Taxon e is more closely related to g Think about most common recent ancestor Questions of relatedness
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G. Polytomies Polytomies 78
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So far we have been discussing bifurcating trees These are trees in which each internal node gives rise to two descendant branches. Polytomies
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Sometimes we draw trees in which some nodes have three or more descendant branches. Such nodes are called polytomies and they usually reflect uncertainty
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Unformatted text preview: about phylogenetic relationships. polytomy Polytomies An extreme case of ignorance: a completely unresolved bush polytomy Polytomies There are three possible resolutions of this three-branched polytomy (assuming that the true tree is bifurcating) polytomy Polytomies Resolution 1: The beetle is more closely related to (fly + moth) than the wasp is polytomy * Polytomies * Resolution 1: The beetle is more closely related to (fly + moth) than the wasp is Polytomies polytomy Resolution 2: The wasp is more closely related to (fly + moth) than the beetle * Polytomies Resolution 2: The wasp is more closely related to (fly + moth) than the beetle * Polytomies polytomy What is the third possibility? Polytomies Resolution 3: Wasp and beetle are each others closest relatives Polytomies...
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This note was uploaded on 11/18/2010 for the course BIS 2C 54181 taught by Professor Eisen during the Fall '10 term at UC Davis.

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Bis2CFall10.Lecture2 - about phylogenetic relationships polytomy Polytomies An extreme case of ignorance a completely unresolved bush polytomy

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