Behind Every Great Tree is a Great (Phylogenetic) Network

In Francis and Steel (2015), it was shown that there exists non-trivial networks on 4 leaves upon which the distance metric affords a metric on a tree which is not the base tree of the network. In this paper we extend this result in two directions. We show that for any tree T there exists a family of non-trivial HGT networks N for which the distance metric dN affords a metric on T . We additionally provide a class of networks on any number of leaves upon which the distance metric affords a metric on a tree which is not the base tree of the network. The family of networks are all “floating” networks, a subclass of a novel family of networks introduced in this paper, and referred to as “versatile” networks. Versatile networks are then characterised. Additionally, we find a lower bound for the number of ‘useful’ HGT arcs in such networks, in a sense explained in the paper. This lower bound is equal to the number of HGT arcs required for each floating network in the main results, and thus our networks are minimal in this sense.