Significance tests for RCI, SCI and GER values by randomization

Chipmunk Basic code for the Macintosh, whether older versions, OSX, MacBooks, and Intel


  • Calculates Relative Completeness Index (RCI) (Benton 1994), Stratigraphic Consistency Index (SCI) (Huelsenbeck 1994), and Gap Excess Ratio (GER) (Wills 1999) given one or more cladistic topologies and stratigraphic range data for up to 74 terminal taxa.

  • Can be used to assay large numbers of trees from PAUP files, reporting those trees with the best fit to stratigraphy. Can be used interactively with MACCLADE to investigate the effects of moving branches on RCI, SCI and GER.

  • Randomly permutes the assignment of stratigraphic ranges among taxa, while holding tree topologies constant. Re-calculates RCI and SCI values, and repeats this process a given number of times to yield a distribution of values. Tests whether the RCI and SCI values for the original data differ significantly from the random distributions.

  • Tabulates trees by RCI, SCI and GER, and the deviation of these indices from random.


    To use the program, you need to do three things:

  • Download Ghosts 2.3 from the bottom of Matt Wills' home page.

  • Download the appropriate version of Chipmunk Basic from Ronald Nicholson's Basic page.

  • E-mail Matt Wills for the password. This helps him keep track of who's using the program, and also enables him to inform you of any updates.