Wagner method tree building

  1. count the number of steps between each group and the outgroup (a difference equals a step). keep in mind that what this actually represents is the number of steps that occur between this group and the ancestor (node) shared with the outgroup.
  2. start with the group that has the smallest number of steps from the node shared with the outgroup. continue in ascending order.
    • when adding a taxon to the tree, you add it to the place that requires the fewest evolutionary steps (or changes).
    • you need to evaluate all nodes (not counting the outgroup) and all terminal branches (not the outgroup).
  3. after you attach a taxon to the tree, you should evaluate the character states for the node you just created.
  4. when you are done, if there are any polytomies, map the characters onto the tree to see if you can resolve them.