Phylogenetic tree

A phylogenetic tree is a tree showing the evolutionary interrelationships among various species or other entities that are believed to have a common ancestor. A phylogenetic tree is a form of a 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. Each node in a phylogenetic tree is called a taxonomic unit. Internal nodes are generally referred to as Hypothetical Taxonomic Units (HTUs) as they cannot be directly observed.

Related Topics:
Tree - Evolution - Species - Common ancestor - Cladogram - Time

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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. Figure 1 depicts a rooted phylogenetic tree, which has been colored according to the three-domain system (Woese 1998).

Related Topics:
Directed - Imputed - Three-domain system - Woese

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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. Figure 2 depicts an unrooted phylogenetic tree¹ for myosin, a superfamily of proteins. Links to other pictures are given in the pictures on the web subsection below.

Related Topics:
Myosin - Superfamily - Protein - Pictures on the web

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There are three main methods of constructing phylogenetic trees: distance-based methods such as neighbour-joining, parsimony-based methods such as maximum parsimony, and character-based methods such as maximum likelihood or Bayesian inference.

Related Topics:
Neighbour-joining - Parsimony - Maximum parsimony - Maximum likelihood - Bayesian inference

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