Direct Calculation of a Tree Length Using a Distance Matrix |
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Authors: | Yves Pauplin |
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Affiliation: | (1) Laboratoire de Biométrie, Génétique et Biologie des Populations, UMR 5558, Université Claude Bernard, 69622 Villeurbanne Cedex, France, FR |
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Abstract: | Comparative studies of tree-building methods have shown minimum evolution to be in general an accurate criterion for selecting a true tree. To improve the use of this criterion, this paper proposes a method for rapidly and directly calculating a length of a dichotomous tree without having to resort to branch length calculations. This direct calculation (DC) method applies to the complete final topology, giving equal importance to each branch after a dichotomy. According to this method, the tree length S DC is S DC =∑ i ∑ j (D ij /2 Bij ) = (∑ i ∑D ij 2 Bmax−Bij )/2 Bmax −1 where D ij is the observed distance between taxa i and j, B ij is the number of branches connecting i and j, Bmax is the greatest B ij in the tree, and the powers of two are due to the dichotomy of the tree. This tree length expression may be used as a rapid method for selecting the shortest tree from a set of hypothetical or subobtimal trees. Received: 2 March 2000 / Accepted: 24 March 2000 |
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Keywords: | : Phylogenetic trees — Distance matrix — Minimum-evolution method — Least square estimates — Cetacean phylogeny — Tree rooting |
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