Addition of Darwinʹs Third Dimension to Phyletic Trees

A three-dimensional (3D) approach for visualizing the phyletic relationship of living animals is proposed and developed as an alternative to current two-dimensional (2D) evolutionary trees. The 3D tree enhances visualization and qualitative analysis since it simultaneously provides topological (tree-structure) and spatial information (based upon genetically measured distances). However, the meaning of the third dimension, particularly its relationship to temporal processes, and further quantitative analyses emerge as open questions. Our method consists of two phases. First, a 3D representation of the genetic relationships of a related group of extant animals is produced using an optimization algorithm developed here. Second, linear connections are added to suggest a visual representation of the differing evolutionary trajectories of the organisms involved on the basis of a 2D tree algorithm. The method is applied to a set of distantly related Caenophidian snakes, and the resulting relationships are analysed. The discussions here are meant to stimulate the generation of 3D trees in the goal of complementing standard 2D views and perhaps ultimately, improving our classification of evolutionary relationships.