Characterizing Compatibility and Agreement of Unrooted Trees via Cuts in Graphs

TL;DR

This paper explores the problem of constructing supertrees that summarize multiple unrooted phylogenetic trees, providing new characterizations of compatibility and agreement through graph cuts and triangulations.

Contribution

It introduces a novel characterization of compatibility and agreement of unrooted trees using minimal cuts in display graphs and triangulation concepts.

Findings

Compatibility characterized by minimal cuts in display graphs.

Agreement characterized through new graph-theoretic conditions.

Provides a framework linking compatibility with split compatibility.

Abstract

Deciding whether there is a single tree -a supertree- that summarizes the evolutionary information in a collection of unrooted trees is a fundamental problem in phylogenetics. We consider two versions of this question: agreement and compatibility. In the first, the supertree is required to reflect precisely the relationships among the species exhibited by the input trees. In the second, the supertree can be more refined than the input trees. Tree compatibility can be characterized in terms of the existence of a specific kind of triangulation in a structure known as the display graph. Alternatively, it can be characterized as a chordal graph sandwich problem in a structure known as the edge label intersection graph. Here, we show that the latter characterization yields a natural characterization of compatibility in terms of minimal cuts in the display graph, which is closely related to compatibility of splits. We then derive a characterization for agreement.