1. Cladistics Making and testing hypotheses of relationship. 28 May 2015 Cladistics2108.ppt1

2. HYPOTHESIS of relationship 28 May 2015 Cladistics2108.ppt2

3. 28 May 2015 Cladistics2108.ppt3 Cladistics Grouping by common descent. 3-taxon statement:  A and B are more closely related to each other than either is to C.

4. 28 May 2015 Cladistics2108.ppt4 MONOPHYLETIC group(s): Grouping of species including all descendants of a common ancestor and the common ancestor.

5. 28 May 2015 Cladistics2108.ppt5 POLYPHYLETIC group [Linnaeus] states as follows: “On account of their warm bilocular heart, their lungs, their moveable eyelids, their hollow ears, penem intrantem feminam mammis lactantem, …” “I take the good old-fashioned ground that the whale is a fish… a whale is a spouting fish with a horizontal tail.” o Melville, H. 1851. Moby Dick, Chapter XXXII.

6. 28 May 2015 Cladistics2108.ppt6 POLYPHYLETIC group(s) Include one or more species not descended from the same ancestor as the other members. TO BE AVOIDED!!!!!!!

7. 28 May 2015 Cladistics2108.ppt7 BUT, lineages, true common ancestors, are unknown. ALL we really know are modern species. Fossil specimens could be ancestors, or extinct side branches, of the family tree.

8. 28 May 2015 Cladistics2108.ppt8 HOW TO RECOGNIZE A MONOPHYLETIC GROUP: Classification by shared derived characters only. primitive &/or convergent similarities will mislead.

9. 28 May 2015 Cladistics2108.ppt9 Shared derived character: = Homology = “Distinguishing character.”  Trait, characteristic, or feature of a group found in every member of the group and not in any other group.

10. 28 May 2015 Cladistics2108.ppt10 Cladistics Avoids bias of researcher, authority. Grouping (classification) = scientific hypothesis.  Testable by congruence of characters  Repeatable.

11. Cladistics Reading a cladogram X-axis Y-axis Line, line segment Node, branching point Line end 28 May 2015 Cladistics2108.ppt11

12. Cladistics 28 May 2015 Cladistics2108.ppt12