An Improved Bipartition Cover Bound for the Multispecies Coalescent Model

Fuente: arXiv
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Autor principal: McNulty, Zachary
Formato: Preprint
Publicado: 2026
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author McNulty, Zachary
author_facet McNulty, Zachary
contents Bipartition cover probabilities quantify whether a collection of gene trees contains every bipartition of the underlying species tree, a condition that underlies finite-sample guarantees for summary methods such as ASTRAL. We study this problem under the multispecies coalescent (MSC) model and derive topology-free upper bounds on the number of loci required to obtain a bipartition cover with prescribed confidence, improving upon the existing bounds of Uricchio et al. (2016). Practically, our bounds remain below biologically realistic numbers of loci across a substantially broader range of parameter settings, expanding their usefulness for empirical datasets. Theoretically, our analysis sharpens our understanding of coalescence under the MSC model and develops new asymptotics for these bounds and absorption times under Kingman's coalescent in the natural short branch regime. We further compare our new bounds with existing work using simulations under a variety of different species-tree topologies.
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id arxiv_https___arxiv_org_abs_2604_09509
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle An Improved Bipartition Cover Bound for the Multispecies Coalescent Model
McNulty, Zachary
Probability
Populations and Evolution
Bipartition cover probabilities quantify whether a collection of gene trees contains every bipartition of the underlying species tree, a condition that underlies finite-sample guarantees for summary methods such as ASTRAL. We study this problem under the multispecies coalescent (MSC) model and derive topology-free upper bounds on the number of loci required to obtain a bipartition cover with prescribed confidence, improving upon the existing bounds of Uricchio et al. (2016). Practically, our bounds remain below biologically realistic numbers of loci across a substantially broader range of parameter settings, expanding their usefulness for empirical datasets. Theoretically, our analysis sharpens our understanding of coalescence under the MSC model and develops new asymptotics for these bounds and absorption times under Kingman's coalescent in the natural short branch regime. We further compare our new bounds with existing work using simulations under a variety of different species-tree topologies.
title An Improved Bipartition Cover Bound for the Multispecies Coalescent Model
topic Probability
Populations and Evolution
url https://arxiv.org/abs/2604.09509