Review of phylogenies

Remember that phylogeny refers to the evolutionary relationships among species. The process of evolution of more than one (usually two) new species from a pre-existing species is called speciation and can be represented as follows:

Reading tree diagrams of phylogeny:

Phylogenies are typically diagrammed as trees; the shape of these trees can vary, but all can be interpreted as follows. Lines with names associated with them refer to species or groups of species all more closely related to each other than to other groups on the tree. Following these lines back to the points where they join other lines leads to ancestral species to the named groups. Lines that lead back to the same line represent species that share a common ancestor.

Here are three phylogenetic trees; all represent the same pattern of phylogenetic relationship among the species shown. Be sure to study these until you can see that all are the same. In this exercise you will need to be able to interpret phylogenetic tree diagrams drawn by different people in different ways.

Return to lab exercise on phylogeny