The space of multifurcating ranked tree shapes: enumeration, lattice structure, and Markov chains

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Hauptverfasser: Zhang, Julie, Rosenberg, Noah A., Palacios, Julia A.
Format: Preprint
Veröffentlicht: 2025
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author Zhang, Julie
Rosenberg, Noah A.
Palacios, Julia A.
author_facet Zhang, Julie
Rosenberg, Noah A.
Palacios, Julia A.
contents Coalescent models of bifurcating genealogies are used to infer evolutionary parameters from molecular data. However, there are many situations where bifurcating genealogies do not accurately reflect the true underlying ancestral history of samples, and a multifurcating genealogy is required. The space of multifurcating genealogical trees, where nodes can have more than two descendants, is largely underexplored in the setting of coalescent inference. In this paper, we examine the space of rooted, ranked, and unlabeled multifurcating trees. We recursively enumerate the space and then construct a partial ordering which induces a lattice on the space of multifurcating ranked tree shapes. The lattice structure lends itself naturally to defining Markov chains that permit exploration on the space of multifurcating ranked tree shapes. Finally, we prove theoretical bounds for the mixing time of two Markov chains defined on the lattice, and we present simulation results comparing the distribution of trees and tree statistics under various coalescent models to the uniform distribution on this tree space.
format Preprint
id arxiv_https___arxiv_org_abs_2506_10856
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The space of multifurcating ranked tree shapes: enumeration, lattice structure, and Markov chains
Zhang, Julie
Rosenberg, Noah A.
Palacios, Julia A.
Probability
Combinatorics
Populations and Evolution
Coalescent models of bifurcating genealogies are used to infer evolutionary parameters from molecular data. However, there are many situations where bifurcating genealogies do not accurately reflect the true underlying ancestral history of samples, and a multifurcating genealogy is required. The space of multifurcating genealogical trees, where nodes can have more than two descendants, is largely underexplored in the setting of coalescent inference. In this paper, we examine the space of rooted, ranked, and unlabeled multifurcating trees. We recursively enumerate the space and then construct a partial ordering which induces a lattice on the space of multifurcating ranked tree shapes. The lattice structure lends itself naturally to defining Markov chains that permit exploration on the space of multifurcating ranked tree shapes. Finally, we prove theoretical bounds for the mixing time of two Markov chains defined on the lattice, and we present simulation results comparing the distribution of trees and tree statistics under various coalescent models to the uniform distribution on this tree space.
title The space of multifurcating ranked tree shapes: enumeration, lattice structure, and Markov chains
topic Probability
Combinatorics
Populations and Evolution
url https://arxiv.org/abs/2506.10856