Revisiting Shao and Sokal’s B2 index of phylogenetic balance

Measures of phylogenetic balance, such as the Colless and Sackin indices, play an important role in phylogenetics. Unfortunately, these indices are specifically designed for phylogenetic trees, and do not extend naturally to phylogenetic networks (which are increasingly used to describe reticulate e...

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Bibliographic Details
Main Authors: Bienvenu, F. (Author), Cardona, G. (Author), Scornavacca, C. (Author)
Format: Article
Language:English
Published: Springer Science and Business Media Deutschland GmbH 2021
Subjects:
Online Access:View Fulltext in Publisher
LEADER 02259nam a2200301Ia 4500
001 10.1007-s00285-021-01662-7
008 220427s2021 CNT 000 0 und d
020 |a 03036812 (ISSN) 
245 1 0 |a Revisiting Shao and Sokal’s B2 index of phylogenetic balance 
260 0 |b Springer Science and Business Media Deutschland GmbH  |c 2021 
856 |z View Fulltext in Publisher  |u https://doi.org/10.1007/s00285-021-01662-7 
520 3 |a Measures of phylogenetic balance, such as the Colless and Sackin indices, play an important role in phylogenetics. Unfortunately, these indices are specifically designed for phylogenetic trees, and do not extend naturally to phylogenetic networks (which are increasingly used to describe reticulate evolution). This led us to consider a lesser-known balance index, whose definition is based on a probabilistic interpretation that is equally applicable to trees and to networks. This index, known as the B2 index, was first proposed by Shao and Sokal (Syst Zool 39(3): 266–276, 1990). Surprisingly, it does not seem to have been studied mathematically since. Likewise, it is used only sporadically in the biological literature, where it tends to be viewed as arcane. In this paper, we study mathematical properties of B2 such as its expectation and variance under the most common models of random trees and its extremal values over various classes of phylogenetic networks. We also assess its relevance in biological applications, and find it to be comparable to that of the Colless and Sackin indices. Altogether, our results call for a reevaluation of the status of this somewhat forgotten measure of phylogenetic balance. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature. 
650 0 4 |a algorithm 
650 0 4 |a Algorithms 
650 0 4 |a B2 index 
650 0 4 |a Biological Evolution 
650 0 4 |a Colless index 
650 0 4 |a evolution 
650 0 4 |a Phylogenetic balance 
650 0 4 |a Phylogenetic networks 
650 0 4 |a phylogeny 
650 0 4 |a Phylogeny 
650 0 4 |a Sackin index 
650 0 4 |a Shannon entropy 
700 1 |a Bienvenu, F.  |e author 
700 1 |a Cardona, G.  |e author 
700 1 |a Scornavacca, C.  |e author 
773 |t Journal of Mathematical Biology