What is a synapomorphy?

1. What is a synapomorphy?

2. Terms systematics [taxonomy, phylogenetics] phylogeny/phylogenetic tree cladogram tips, branches, nodes homology apomorphy synapomorhy autapomorphy plesiomorphy symplesiomorphy homoplasy convergence reversal of trait monophyletic paraphyletic polyphyletic tree polarity outgroup ancestral group sister group character congruence topological congruence maximum parsimony People Willi Hennig

3. No Yes Wings Principles of Phylogenetics: Tree Thinking

4. PHYLOGENETIC INFERENCE • Seeks to recover the historical genetic patterns of relationships among organisms

5. PHYLOGENETIC INFERENCE Principles: • Assumes similar features arehomologous until • shown otherwise

6. HOMOLOGY correspondence (morphological, molecular, behavioral) inherited through common ancestry

7. Structural homologies F&H Fig 2.1

8. Uses shared derived features, not shared ancestral ones (Hennig formalized this) PHYLOGENETIC INFERENCE Principles: • Assumes similar features are homologous until • shown otherwise Willi Hennig (1950s-1960s)

9. synapomorphy shared derived character Homo Australopithecus Large braincases

10. High forehead autapomorphy uniquely derived character Australopithecus H. sapiens

11. symplesiomorphy shared ancestral character Australopithecus Homo bipedal

12. synapomorphy shared derived character autapomorphy uniquely derived character symplesiomorphy shared ancestral character

13. PHYLOGENETIC INFERENCE Principles: • Assumes similar features are homologous until • shown otherwise • Uses shared derived features, not shared ancestral • ones (Hennig formalized this) • Treats shared derived features (character states) as markers of historical relatedness

14. PHYLOGENETIC INFERENCE Principles: • Assumes similar features are homologous until • shown otherwise • Uses shared derived features, not shared ancestral • ones (Hennig formalized this) • Treats shared derived features (character states) as • markers of historical relatedness • Same basic logic used for comparative morphology or DNA

15. Tree-speak tip tip tip tip branch branch node

16. A simple example….. TANAGER internal skeleton wings 2 legs feathers “warm-blooded” TREE FROG internal skeleton no wings 4 legs no hair or feathers “cold-blooded” BUMBLE BEE external skeleton wings 6 legs hair “cold-blooded” OPOSSUM Internal skeleton no wings 4 legs hair “warm-blooded”

17. Internal External Character First taking one character at a time…. Character State Character State (1) (0) Skeleton

18. First taking one character at a time…. (1) (1) (1) (0) Internal External Skeleton

19. Yes No Wings But….

20. bird wings are homologous to front legs of frogs and opossum. and NOT to wings of bee so…

21. No Yes, but convergent Wings

22. 2 4 6 Legs But….

23. bird wings are homologous to front legs of frogs and opossum. so birds have 4 legs! so…

24. 4 6 Legs really….

25. Poikilothermic (“cold-blooded”) Endothermic (“warm-blooded”) metabolism (actually bumble bees can be endothermic temporarily…)

26. Hair Just skin Feathers Body covering But….

27. Is hair of opossum and bee really homologous? Hair We can test whether these groups share common ancestry using other characters….

28. External Internal Skeleton 4 6 Legs Poikilothermic (“cold-blooded”) Endothermic (“warm-blooded”) Just skin Feathers Hair Body covering Metabolism Character state trees Yes, but convergent No Wings

29. How can we combine the information from different characters to infer an overall phylogeny? External Internal Yes, but convergent No Skeleton Wings 4 6 Legs Poikilothermic (“cold-blooded”) Endothermic (“warm-blooded”) Just skin Feathers Hair Body covering Metabolism

30. How can we combine the information from different characters to infer an overall phylogeny? If for only a few characters with no conflict, you can do this in your head, but Quantitative methods are now implemented by computer to do this!

31. First, make up a [character x taxon] matrix, converting ancestral states to 0’s and derived to 1’s or 2’s Skeleton Wings Legs Metabolism Covering Bumble bee 0 1 1 0 2 Tree frog 1 0 0 0 0 Tanager 1 2 0 1 1 Opossum 1 0 0 1 2

32. How do we know which state of a character is the ancestral one and which is derived? --Fossils may help show earlier appearance! --Outgroup Analysis States found within a group and also in related groups (outgroups) are more likely to be ancestral than those found only within the group

33. States found within a group and also in related groups (outgroups) are more likely to be ancestral than those found only within the group (ingroup) endothermic outgroup ingroup Poikilothermy is likely to be ancestral in frog/bird/mammal group poikilothermic

34. Skeleton Wings Legs Metabolism Covering Bumble bee 0 1 1 0 2 Tree frog 1 0 0 0 0 Tanager 1 2 0 1 1 Opossum 1 0 0 1 2

35. These are then “optimized” onto possible phylogenetic trees, and the tree that requires the fewest total changes of character state is chosen as the most likely (basic parsimony analysis) (It is also possible to make decisions among trees based upon the likelihood of alternative changes, rather than simply the evolutionarily “shortest” tree (we’ll see this with molecular data)

36. Using only the shared derived states….! 1 2 2 2 1 1 1 1 skeleton legs metabolism covering wings Skel Wing Leg Metab Cov Bumble bee 0 1 2 1 0 Tree frog 1 0 0 0 0 1 Tanager 1 2 0 1 Opossum 1 0 2 0 1

37. Feathers Just skin Hair Body covering Poikilothermic (“cold-blooded”) Endothermic (“warm-blooded”) Metabolism How do we resolve differences in relationships implied by different characters (character state conflict)?

38. This tree requires 8 steps, including an extra step (homoplasy) due to convergence in covering character 1 2 2 2 1 1 1 1 skeleton legs metabolism covering wings

39. 1 Using only the shared derived states….! How many steps or evolutionary changes result from mapping the different character states onto these two other tree topologies? Using the principle of maximum parsimony, which tree would be selected as the more likely ? 2 2 2 1 1 1 1 8 steps steps steps Skel Wing Leg Metab Cover Bumble bee 0 1 1 0 2 Tree frog 1 0 0 0 0 1 Tanager 1 2 0 1 Opossum 1 0 0 1 2 (See next pg.)