Phylogenetic treeA phylogenetic tree is a tree showing the evolutionary interrelationships between various species or other entities that are believed to have a common ancestor. A phylogenetic tree is a form of cladogram.
In a phylogenetic tree, each node with descendants represents the most recent common ancestor of the descendants, and edge lengths correspond to time estimates.
A rooted phylogenetic tree is a directed tree with a unique node corresponding to the (usually imputed) most recent common ancestor of all the entities at the leaves of the tree.
An unrooted phylogenetic tree is, loosely speaking, a tree derived from a rooted phylogenetic tree by omitting the root. More precisely, it is a forest of rooted phylogenetic trees depicted so that the roots are all linked. Here is a thumbnail of an unrooted tree¹:
Links to other pictures are given in the Pictures on the web subsection below.
Pictures on the web