How much can evolved characters tell us about the tree that generated them?

TL;DR

This paper reviews recent theoretical results on the limits of phylogenetic signal in evolved characters, exploring bounds, model parameters, and the impact of character state space size on tree reconstruction accuracy.

Contribution

It provides new bounds and insights on the amount of phylogenetic information characters can carry, including extensions for rate variation and large state spaces.

Findings

Explicit bounds on ancestral state reconstruction probability

Phase transition in sequence length needed for accurate tree inference

Impact of large state spaces on character-based phylogenetic analysis

Abstract

In this paper we review some recent results that shed light on a fundamental question in molecular systematics: how much phylogenetic `signal' can we expect from characters that have evolved under some Markov process? There are many sides to this question and we begin by describing some explicit bounds on the probability of correctly reconstructing an ancestral state from the states observed at the tips. We show how this bound sets upper limits on the probability of tree reconstruction from aligned sequences, and we provide some new extensions that allow site-to-site rate variation or a covarion mechanism. We then explore the relationship between the number of sites required for accurate tree reconstruction and other model parameters - such as the number of species, and substitution probabilities, and we describe a phase transition that occurs when substitution probabilities exceed a critical value. In the remainder of this paper we turn to models of character evolution where the state space is assumed to be either infinite or very large. These models have some relevance to certain types of genomic data (such as gene order) and here we again investigate how many characters are required for accurate tree reconstruction.