Related Experiment Video
Updated: Jan 23, 2026

A Practical Guide to Phylogenetics for Nonexperts
Published on: February 5, 2014
A balance index for phylogenetic trees based on rooted quartets
Tomás M Coronado1,2, Arnau Mir1,2, Francesc Rosselló3,4
1Department of Mathematics and Computer Science, University of the Balearic Islands, 07122, Palma, Spain.
Abstract:
We define a new balance index for rooted phylogenetic trees based on the symmetry of the evolutive history of every set of 4 leaves. This index makes sense for multifurcating trees and it can be computed in time linear in the number of leaves. We determine its maximum and minimum values for arbitrary and bifurcating trees, and we provide exact formulas for its expected value and variance on bifurcating trees under Ford's [Formula: see text]-model and Aldous' [Formula: see text]-model and on arbitrary trees under the [Formula: see text]-[Formula: see text]-model.
Related Concept Videos
Phylogenetic Trees
Acid-Base Balance
When the pH of arterial blood rises above 7.45, it results in a condition called alkalosis. Conversely, a drop below 7.35 leads to...
Disorders of Acid-Base Balance
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
Respiratory Regulation of Acid-Base Balance
When carbon dioxide levels increase in the blood, more H+ and HCO3⁻ are...
The Tree of Life - Bacteria, Archaea, Eukaryotes
Renal Regulation of Acid-Base Balance
In the kidneys, cells within the proximal convoluted tubules (PCT) and the collecting ducts secrete hydrogen ions (H+) into the tubular fluid. Specifically, in the PCT, Na+/H+ antiporters secrete H+ while reabsorbing Na+.
However, the intercalated cells in...

