2021/11/25 by Sagi Snir, Snir, Sagi, Osnat Weissberg +3
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #05C05 #05C35 #68R05 #92B10 #Chromosomal and Genetic Variations #Combinatorics (math.CO) #Discrete Mathematics (cs.DM) #FOS: Biological sciences #FOS: Computer and information sciences #FOS: Mathematics #Genome Rearrangement Algorithms #Genomics and Phylogenetic Studies #Populations and Evolution (q-bio.PE)
paper · pdf · doi:10.48550/arxiv.2111.13101
openalex publication_date 2021/11/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Let T be an arbitrary phylogenetic tree with n leaves. It is well-known that the average quartet distance between two assignments of taxa to the leaves of T is \frac 23 \binomn4. However, a longstanding conjecture of Bandelt and Dress asserts that (\frac 23 +o(1))\binomn4 is also the \em maximum quartet distance between two assignments. While Alon, Naves, and Sudakov have shown this indeed holds for caterpillar trees, the general case of the conjecture is still unresolved. A natural extension is when partial information is given: the two assignments are known to coincide on a given subset of taxa. The partial information setting is biologically relevant as the location of some taxa (species) in the phylogenetic tree may be known, and for other taxa it might not be known. What can we then say about the average and maximum quartet distance in this more general setting? Surprisingly, even determining the \em average quartet distance becomes a nontrivial task in the partial information setting and determining the maximum quartet distance is even more challenging, as these turn out to be dependent of the structure of T. In this paper we prove nontrivial asymptotic bounds that are sometimes tight for the average quartet distance in the partial information setting. We also show that the Bandelt and Dress conjecture does not generally hold under the partial information setting. Specifically, we prove that there are cases where the average and maximum quartet distance substantially differ.