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** Ktreedist 1.0 **

**Ktreedist** is an open-source computer program written in Perl scripting language that calculates the minimum branch length distance (or K tree score) from one phylogenetic tree to another.The K tree score provides a measure of the difference in both topology and branch lengths between two trees after scaling one of them to have a global divergence as similar as possible to the other tree. In order to calculate the K score, the program first calculates the scale factor that approximates as much as possible the global divergence of a comparison tree to that of a reference tree; then it scales the comparison tree by this factor âKâ. Second, the program calculates the branch length distance of Kuhner and Felsenstein between the scaled comparison tree and the reference tree. Our measure is thus the minimum branch length distance you can get from one tree to another after scaling one of them. It can be useful to compare the shape (variation in branch lengths or local molecular clocks) between two phylogenetic trees independently of the global rates. Ktreedist can be used in any operating system with a Perl interpreter.

Soria-Carrasco, V., Talavera, G., Igea, J., and Castresana, J. (2007). The K tree score: quantification of differences in the relative branch length and topology of phylogenetic trees. Bioinformatics 23, 2954-2956.

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