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Inferring phylogenies : closely related species should have traits in common – inherited from their common ancestor ( ho

Tracing evolutionary history. Inferring phylogenies : closely related species should have traits in common – inherited from their common ancestor ( homology ) – informative traits are shared derived traits ( homologies that are not the ancestral state)

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Inferring phylogenies : closely related species should have traits in common – inherited from their common ancestor ( ho

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  1. Tracing evolutionary history • Inferring phylogenies: • closely related species should have traits in common • – inherited from their common ancestor (homology) • – informative traits are shared derived traits • (homologies that are not the ancestral state) • identifying shared derived traits requires determining: • – homologies • – ancestralvs. derived states (direction of change)

  2. outgroup – provides information about ancestral state – roots the tree Which traits are ancestral? Which traits are derived?

  3. 3 possible trees – what changes are implied? – which traits are informative? – which tree is best? parsimony –

  4. Use parsimony to build a phylogeny: outgroup? homologies? ancestral vs. derived states? shared derived traits?

  5. Tracing evolutionary history • Inferring phylogenies: • closely related species should have traits in common • – inherited from their common ancestor (homology) • – informative traits are shared derived traits • (homologies that are not the ancestral state) • complications arise when traits are shared for other reasons • – • –

  6. convergence –

  7. Shared traits 1) Homology –

  8. Shared traits 1) Homology – 2) Convergent evolution –

  9. long head? • hair? • smile? • ears? • nose? H – shared derived trait H – convergence

  10. Same pattern can reflect different evolutionary histories convergent evolution of hair reversal to hairless H – H – OR LH LH N N SM SM E E

  11. 0 0 1 1 2 2 3 3 4 4 1 A . . . . 2 C G G . . 3 G . . . . 4 C . . . . 5 G . A T T 6 G . . . . 7 T . . C C 8 C . . . . 9 A . . . . 10 T . . A . 11 T . . . . 12 A . . . . DNA base sp 0 sp 1 sp 2 sp 3 sp 4 1 A . . . . 2 C G G . . 3 G . . . . 4 C . . . . 5 G . T T T 6 G . . . . 7 T . . C C 8 C . . . . 9 A . . . . 10 T . . A . 11 T . . . . 12 A . . . . 12 A T T T T sp 0 sp 1 sp 2 sp 3 sp 4 Phylogenetic analysis of molecular data 12 A T T T T

  12. What are phylogenies good for? • Tracing evolutionary relationships • e.g.: disease transmission (problem set 4) • coevolution (in text) • tree of life • adaptive radiation

  13. Evolutionary relationships – the tree of life

  14. Evolutionary relationships – the tree of life

  15. Evolutionary relationships – the tree of life

  16. Evolutionary relationships – adaptive radiation on islands

  17. What are phylogenies good for? • Tracing evolutionary relationships • e.g.: disease transmission (problem set 4) • coevolution (in text) • tree of life • adaptive radiation • Studying trait evolution • requires independent data • e.g.: origin of whales (in text) • evolution of viviparity map morphological traits onto molecular phylogeny

  18. Trait evolution – origin of whales

  19. Trait evolution – evolution of viviparity in Sceloporus Sceloporus (a lizard genus) – some populations lay eggs, others bear live young

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