Bis2CFall10.Lecture4.final

Bis2CFall10.Lecture4 - 1 Lecture 4 BIS 002C BIODIVERSITY AND THE TREE OF LIFE Lecture 4 Character State Reconstruction and Phylogenetic Inference

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Unformatted text preview: 1 Lecture 4: BIS 002C BIODIVERSITY AND THE TREE OF LIFE Lecture 4: Character State Reconstruction and Phylogenetic Inference Wednesday, September 29, 2010 2 Where we are going and where we have been • Previous lecture : ! 3: Characters • Current Lecture: ! 4. Character State Reconstruction and Phylogenetic Inference • Next Lecture: ! 5. Phylogenetic Inference Wednesday, September 29, 2010 3 Lecture 4 Outline • Trait evolution continued ! Homoplasy revisited ! Principle of parsimony ! Character state reconstruction • Phylogenetic inference ! General concept ! Parsimony again ! Unrooted trees ! Identifying most parsimonious tree Wednesday, September 29, 2010 A. Homoplasy revisited 4 Wednesday, September 29, 2010 Similarities not all due to homology • Regarding similarities between organisms: ! Some may be the result of homology (i.e., shared ancestry) ! But others are due to independent origins in different branches. • Traits that are similar for reasons other than inheritance from a common ancestor are called homoplastic traits or homoplasies . 5 Wednesday, September 29, 2010 a b c d e h g f Example 6 Wednesday, September 29, 2010 • Convergent evolution —independently evolved traits subjected to similar selection pressures may become superficially similar. • Parallel evolution —repeated evolutionary changes that occur independently in multiple lineages. • Evolutionary reversal —the reappearance of an ancestral trait in a group that had previously acquired a derived trait. Possible paths leading to homoplasy 7 Wednesday, September 29, 2010 a b c d e h g f Example 8 Wednesday, September 29, 2010 B. Character state reconstruction Character state reconstruction 9 Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 10 Character state reconstruction Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 11 Character state reconstruction What is the most plausible pattern for the character states along the tree? Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 12 In theory, each node could have either of the two states Character state reconstruction Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 13 One possible pattern: Character state reconstruction Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 14 Another possible pattern Character state reconstruction Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 15 A third possible pattern Character state reconstruction Wednesday, September 29, 2010 a Bats c d e Birds g f Mammals Reptiles + 16 Many others Character state reconstruction Wednesday, September 29, 2010 17 • How do we decide which pattern is the most plausible?...
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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.Lecture4 - 1 Lecture 4 BIS 002C BIODIVERSITY AND THE TREE OF LIFE Lecture 4 Character State Reconstruction and Phylogenetic Inference

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