NEW MEASUREMENTS OF DISTRIBUTION OF HOMOPLASY AND RELIABILITY OF PARSIMONIOUS CLADOGRAMS

Levels of homoplasy, measured by consistency index (CI) or retention i ndex (RI), have been commonly used as indicators of reliability of par simonious cladograms. Less attention has been paid to distribution of homoplasy which, however, may be another important parameter for estim ating the reliability of cladograms. Average unit character consistenc y (AUCC), measuring distribution of homoplasy among the characters on parsimonious cladograms, is defined as the average of total unit chara cter consistencies. When cladograms with the same CI are compared, the one with the largest AUCC also has the most asymmetric distribution o f homoplasy, i.e., it is compatible with the largest portion of the ch aracters, and homoplasy is concentrated in the smallest portion of cla distically unreliable or fast evolved characters of this cladogram. Ho moplasy distribution index (HDI) is defined as the difference between the AUCC and CI, and can be used to compare distribution of homoplasy among cladograms with similar levels of homoplasy. A new measurement o f the reliability of parsimonious cladograms, homoplasy distribution r atio (HDR), is defined as the ratio of the HDI to the homoplasy index (HI).