For application to characters, see ordered. As applied to trees, it refers to whether distances measured along the branches of the tree add up to the observed distances (from a matrix of pair-wise distance comparisons among terminal taxa).

    The determination of positional homology for molecular sequences, involving the juxtaposition of amino acids or nucleotides in homologous molecules.

    See phylesis.

    See homoplasy.

    A relatively derived or advanced or unique character state (cf. autapomorphy, synapomorphy, plesiomorphy, symplesiomorphy).

    A tree that displays historical relationships among geographic areas, rather than phylogenetic relationships among taxa.

    The possession by an organism of a particular feature, e.g. this tree is rough-barked, that tree is half-barked (cf. character and character states).

    An apomorphy in a terminal taxon; diagnoses the terminal but is uninformative about relationships to other terminals; therefore of no use for cladistic tree-building.

    A character type with only two states (usually given as 0, 1), in which a change in either direction between the states is one step (cf. ordered, unordered, Dollo, irreversible).

    Any heritable attribute of organisms that varies among terminal taxa, and so is useful for phylogenetic reconstruction.