EEB362H1 Chapter Notes - Chapter 4: Convergent Evolution, Willi Hennig, Cladistics
11 Oct 2016
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Complete cladist chapter 4: tree building and optimization. Basically same thing as inclusion/exclusion rule: but less tedious b/c don"t have to make all those single-character trees. Can look at matrix and circle potential groupings. Look for obvious groups w/ lots of synapomorphies and try to link them together. Optimal tree = 1 out of many possible trees that meets particular criterion: = tree length. Maximum parsimony criterion: optimal tree = tree that has shortest length for given data matrix: could be only 1 optimal tree, could be many optimal tree. If have lots of optimal tree = equally parsimonious trees. Need to minimize number of homoplasies and maximize number of apomorphies. Can still have homoplasy, but want minimal amount. Optimization is sthg you do after the tree is already built: used to evaluate built trees. Also had assumptions about character evolution: e. g. Weight of transformation between characters = assumption investigator makes about nature of character evolution.
