Classes of Explicit Phylogenetic Networks and their Biological and Mathematical Significance

TL;DR

This paper reviews various classes of rooted phylogenetic networks, their biological significance, and how structural constraints can improve the estimation process from genomic data.

Contribution

It provides a comprehensive classification of phylogenetic network subclasses and discusses their biological and mathematical implications.

Findings

Classifications of phylogenetic networks are linked to biological phenomena

Structural constraints aid in scalable network estimation

Analysis of network subclasses enhances understanding of evolution

Abstract

The evolutionary relationships among organisms have traditionally been represented using rooted phylogenetic trees. However, due to reticulate processes such as hybridization or lateral gene transfer, evolution cannot always be adequately represented by a phylogenetic tree, and rooted phylogenetic networks that describe such complex processes have been introduced as a generalization of rooted phylogenetic trees. In fact, estimating rooted phylogenetic networks from genomic sequence data and analyzing their structural properties is one of the most important tasks in contemporary phylogenetics. Over the last two decades, several subclasses of rooted phylogenetic networks (characterized by certain structural constraints) have been introduced in the literature, either to model specific biological phenomena or to enable tractable mathematical and computational analyses. In the present manuscript, we provide a thorough review of these network classes, as well as provide a biological interpretation of the structural constraints underlying these networks where possible. In addition, we discuss how imposing structural constraints on the network topology can be used to address the scalability and identifiability challenges faced in the estimation of phylogenetic networks from empirical data.