Reconstructing fully-resolved trees from triplet cover distances

TL;DR

This paper demonstrates that certain leaf pair distance sets, called covers, uniquely determine a tree's structure and weights, and provides a polynomial-time algorithm for reconstruction, advancing understanding in phylogenetics.

Contribution

It establishes that specific cover sets of leaf pairs suffice for unique tree reconstruction and offers a polynomial-time algorithm for this process.

Findings

Unique reconstruction from cover sets is possible.

Polynomial-time algorithm for tree reconstruction.

Relevance to evolutionary genomics applications.

Abstract

It is a classical result that any finite tree with positively weighted edges, and without vertices of degree 2, is uniquely determined by the weighted path distance between each pair of leaves. Moreover, it is possible for a (small) strict subset $\cl$ of leaf pairs to suffice for reconstructing the tree and its edge weights, given just the distances between the leaf pairs in $\cl$. It is known that any set $\cl$ with this property for a tree in which all interior vertices have degree 3 must form a {\em cover} for $T$ -- that is, for each interior vertex $v$ of $T$, $\cl$ must contain a pair of leaves from each pair of the three components of $T-v$. Here we provide a partial converse of this result by showing that if a set $\cl$ of leaf pairs forms a cover of a certain type for such a tree $T$ then $T$ and its edge weights can be uniquely determined from the distances between the pairs of leaves in $\cl$. Moreover, there is a polynomial-time algorithm for achieving this reconstruction. The result establishes a special case of a recent question concerning `triplet covers', and is relevant to a problem arising in evolutionary genomics.