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A reduction algorithm for computing the hybridization number of two trees.

Bordewich, M. and Linz, S. and St. John, K. and Semple, C. (2007) 'A reduction algorithm for computing the hybridization number of two trees.', Evolutionary bioinformatics., 3 . pp. 86-98.


Hybridization is an important evolutionary process for many groups of species. Thus, conflicting signals in a data set may not be the result of sampling or modeling errors, but due to the fact that hybridization has played a significant role in the evolutionary history of the species under consideration. Assuming that the initial set of gene trees is correct, a basic problem for biologists is to compute this minimum number of hybridization events to explain this set. In this paper, we describe a new reduction-based algorithm for computing the minimum number, when the initial data set consists of two trees. Although the two-tree problem is NP-hard, our algorithm always gives the exact solution and runs efficiently on many real biological problems. Previous algorithms for the two-tree problem either solve a restricted version of the problem or give an answer with no guarantee of the closeness to the exact solution. We illustrate our algorithm on a grass data set. This new algorithm is freely available for application at either or

Item Type:Article
Keywords:Hybridization networks, Reticulate evolution, Agreement forest.
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Publisher statement:This work is licensed under a Creative Commons Attribution 3.0 License (
Date accepted:No date available
Date deposited:06 January 2010
Date of first online publication:May 2007
Date first made open access:No date available

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