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Sister taxa   [ Cladistics - Taxonomy ]
Synonym: Sister group

Dictionary of botanic terminology - index of names

  The two clades resulting from the splitting of a single lineage.  

In cladistics: The descendant branches from a node on a cladogram, the two species or higher monophyletic taxon (clades) which meet at a node; or in other words two lineages which diverged from that particular common ancestor. In a phylogeny, the descendants of an ancestor are called "daughters", while the siblings after a speciation event are called "sisters" (so a descendant is a daughter relative to its ancestor and is a sister relative to its other sibling). Note that if either of the daughters undergoes further speciation then the sister to a particular terminal taxon may actually be a group of terminal taxa. Because sister groups share a common ancestor, they are each other's closest relatives.

Sister relationships in a Phylogenetic Tree:

Species 5 is the sister group to species 6

Species 3 is the sister group to species 4

The clade of species 3+4 is the sister group to the clade of species 5+6

The clade of species (3/4)+(5/6) is sister to species 2

Species 1 is sister to the clade containing all the other species
Remember, trees can be rotated at the nodes without changing the topology (i.e. without changing the relationships represented in the tree).





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