PHYLOGENETIC - difference(or similarity between the two taxa These can be clustered by UPGMA(unweighted pair group methods with averages The two

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PHYLOGENETIC INFERENCE The crucial issue in systematics is that there is a history of the organisms we wish to classify, but we don't know that history. We must infer the sequence of branches or evolutionary transformations that have taken place. There is a true phylogeny which we may never know, our task is to collect and analyze data to provide the best estimate of the true phylogeny. We will work some examples that illustrate the difficulty of this task. Phenetics : classification based on overall similarity. See fig. 14.4, pg. 378. Matrix of shared character states . Those taxa with the most number of similar character states are deemed more similar. Distance (or similarity) matrix derived from morphological measurements, genetic distance measures, etc. Each cell in the matrix is a value indicating the degree of
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Unformatted text preview: difference (or similarity) between the two taxa. These can be clustered by UPGMA (unweighted pair group methods with averages). The two most similar (least distant) taxa are joined to form a group (e.g., taxa 1 & 2); the length of each branch is half the distance value between the two taxa. The next most similar taxon (3) is joined to the tree and the distance is calculated as the average of the distance from taxon 1 to taxon 3 and taxon 2 to taxon 3. At each such step in building a tree, the number of taxa in the matrix is reduced by one and new distance values are calculated as the average distance from each member of the group just formed to each taxon outside that group. This process of adding the most similar new taxon to a group is continued until all taxa are joined....
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This note was uploaded on 11/06/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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