Phylogenetic graph models beyond trees

  • Authors:
  • Ulrik Brandes;Sabine Cornelsen

  • Affiliations:
  • Department of Computer & Information Science, University of Konstanz, Box D 67, 78457 Konstanz, Germany;Department of Computer & Information Science, University of Konstanz, Box D 67, 78457 Konstanz, Germany

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2009

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Abstract

A graph model for a set S of splits of a set X consists of a graph and a map from X to the vertices of the graph such that the inclusion-minimal cuts of the graph represent S. Phylogenetic trees are graph models in which the graph is a tree. We show that the model can be generalized to a cactus (i.e. a tree of edges and cycles) without losing computational efficiency. A cactus can represent a quadratic rather than linear number of splits in linear space. We show how to decide in linear time in the size of a succinct representation of S whether a set of splits has a cactus model, and if so construct it within the same time bounds. As a byproduct, we show how to construct the subset of all compatible splits and a maximal compatible set of splits in linear time. Note that it is NP-complete to find a compatible subset of maximum size. Finally, we briefly discuss further generalizations of tree models.