Reconstructing unrooted phylogenetic trees from symbolic ternary metrics

TL;DR

This paper characterizes and reconstructs unrooted phylogenetic trees from symbolic ternary metrics, extending previous work on rooted trees and ultrametrics, and provides algorithms for tree reconstruction.

Contribution

It introduces a characterization of ternary maps for unrooted trees and presents a bottom-up algorithm for reconstructing such trees from these maps.

Findings

Characterization of ternary maps via 4- and 5-point conditions.

Reconstruction algorithm for general unrooted trees.

Additional condition for binary tree identification.

Abstract

In 1998, B\"{o}cker and Dress gave a 1-to-1 correspondence between symbolically dated rooted trees and symbolic ultrametrics. We consider the corresponding problem for unrooted trees. More precisely, given a tree $T$ with leaf set $X$ and a proper vertex colouring of its interior vertices, we can map every triple of three different leaves to the colour of its median vertex. We characterise all ternary maps that can be obtained in this way in terms of 4- and 5-point conditions, and we show that the corresponding tree and its colouring can be reconstructed from a ternary map that satisfies those conditions. Further, we give an additional condition that characterises whether the tree is binary, and we describe an algorithm that reconstructs general trees in a bottom-up fashion.