Improved Fixed-Parameter Algorithms for Minimum-Flip Consensus Trees

  • Authors:
  • Sebastian Böcker;Quang Bao Anh Bui;Anke Truss

  • Affiliations:
  • Friedrich-Schiller-Universität Jena;Friedrich-Schiller-Universität Jena;Friedrich-Schiller-Universität Jena

  • Venue:
  • ACM Transactions on Algorithms (TALG)
  • Year:
  • 2012

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Abstract

In computational phylogenetics, the problem of constructing a consensus tree for a given set of rooted input trees has frequently been addressed. In this article we study the Minimum-Flip Problem: the input trees are transformed into a binary matrix, and we want to find a perfect phylogeny for this matrix using a minimum number of flips, that is, corrections of single entries in the matrix. The graph-theoretical formulation of the problem is as follows: Given a bipartite graph G = (Vt ∪ Vc, E), the task is to find a minimum set of edge modifications such that the resulting graph has no induced path with four edges that starts and ends in Vt, where Vt corresponds to the taxa set and Vc corresponds to the character set. We present two fixed-parameter algorithms for the Minimum-Flip Problem, one with running time O(4.83k + poly(m, n)) and another one with running time O(4.42k + poly(m, n)) for n taxa, m characters, k flips, and poly(m, n) denotes a polynomial function in m and n. Additionally, we discuss several heuristic improvements. We also report computational results on phylogenetic data.