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Hybridisation in non-binary trees

Thursday 20th December 2007 - 14:40 to 15:00
INI Seminar Room 1
Session Chair: 
Charles Semple

Molecular phylogenetics, the study of reconstructing evolutionary trees, is a well-established field of scientific endeavor. However, in certain circumstances, evolution is not best represented by trees. For example, a comparison of gene trees representing a set of taxa and reconstructed for different genetic loci sometimes reveals conflicting tree topologies. These discrepancies are often due to reticulation events such as horizontal gene transfer and hybridization. Assuming that the initial data set is correct, a basic problem is to compute the minimum number of reticulation events to explain the evolutionary history for a set of present-day species.

Recently, it has been shown that a theoretical framework - based on the notion of agreement forests - can be used to calculate the number of reticulation events for two rooted binary phylogenetic trees. Together with two reduction rules, this leads to an algorithm that runs efficiently for many biological examples and gives the exact solution. However, for many data sets, the reconstructed trees are not fully resolved. In this talk, we extend this framework to non-binary trees. Further, we show that the subtree prune and regraft distance between two non-binary trees, which is often used to model reticulate evolution, can be approached in a similar way.

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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons